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Nature Genetics🤖 AI summary
Identifying the Genetic Traces Crops Leave in Soil: A Next-Generation Breeding Method Designing Entire Crop Rotation Systems Beyond Single Varieties
Background Modern agricultural breeding has focused on maximizing the yield of individual crops. While single-variety-centered selection breeding contributed to increasing annual productivity, it created structural limitations such as continuous cropping disorders and the degradation of soil ecosystems. In farmland, crop rotation systems—planting different crops in succession—are widely used to replenish soil fertility and suppress pest proliferation. In actual cultivation, residual organic matter and root exudates remain in the soil even after the previous crop is harvested, directly affecting the growth of subsequent crops in the following season. This is referred to as Plant-Soil Feedback (PSF) or soil legacy. The problem is that existing crop improvement programs have proceeded while completely excluding these soil legacy interactions. Breeders evaluated traits by planting only a single target crop in independent plots, without tracking the impact of changes to the soil microbiome or nutrient balance on subsequent crops planted the following year. While farmers experienced extreme productivity variations depending on the variety combination when planting corn after certain legumes, they attempted to solve the problem by relying on chemical fertilizer and pesticide inputs without identifying the clear cause. Key Findings This Perspective article published in Nature Genetics presents an empirical analysis demonstrating that the biochemical and microbiological footprints left by crops in the soil are not merely environmental factors, but are determined by the variety's inherent genetics. The researchers explained that even within the same crop species, the composition of phenolics and organic acids in root exudates varies depending on which alleles are carried, which in turn determines the structure of the rhizosphere microbial community and the amount of fixed nitrogen. A particularly noteworthy observation is that the magnitude and quality of the soil legacy depend heavily on genetic variation between varieties. According to experimental analysis, certain wheat varieties accumulate beneficial bacteria in the soil that aid in nodule formation for subsequent legumes, whereas other varieties leave pathogenic fungal spores in the soil, inhibiting the initial rooting of the next crop. In other words, the genetic traits of a crop indirectly control not only the current year's yield but also the phenotype of the next crop through the medium of the soil. The research team proposed a complete revision of the traditional breeding system, which used only the single-season yield of a single crop as an indicator. An integrated multi-crop breeding system that optimizes the cumulative productivity and resource use efficiency of the entire rotation cycle, spanning 2 to 4 years, was proposed as an alternative, moving beyond the independent evaluation of individual varieties. The strategy involves quantifying the interactions between the genotypes of preceding and subsequent crops to custom-design genetic combinations so that the previous crop contributes to fertilization and suppresses soil-borne pathogens. Significance and Outlook This proposal provides a new breeding paradigm for the global agricultural industry, which must drastically reduce the use of chemical fertilizers and fungicides. It opens a path to move away from the practice of applying inputs after sowing to maintain soil health, and instead utilize the genetic characteristics of crops themselves as tools for improving the soil environment. Once the genetic compatibility between crops within a rotation system is identified, farmers can secure stable total yields throughout the rotation cycle while minimizing fertilizer input. However, there are significant challenges to overcome before fully implementing this method in the breeding industry. Since the genetic combinations of multiple crops must be cross-validated over several years, the area of breeding test plots and the evaluation period will inevitably increase by three to four times compared to existing methods. Controlling the complexity of Genotype-by-Environment (GxE) interactions, which depend on soil microbiome and climatic conditions, is also a difficult task. The researchers added that the development of technologies to pre-screen soil legacy traits by combining metagenomic analysis with machine learning-based predictive models must proceed in parallel to reduce the cost of large-scale field evaluations.
💡 Seed companies and agricultural operations can develop customized complex seed package products based on this concept. For example, it is anticipated that a business model will emerge to supply farmers with rotation-specific variety sets featuring verified mutual soil feedback synergies, moving away from the practice of selling preceding wheat varieties and subsequent soybean varieties individually. This can be expanded into crop rotation placement prescriptions optimized for regional soil characteristics when combined with precision agriculture data. Amid rising fertilizer and pesticide prices that are increasing the burden of farming costs, designing crop rotations that leverage natural soil metabolic legacies offers a practical alternative to reduce farming expenses while addressing stricter eco-friendly agricultural regulations.
Nature Genetics🤖 AI summary
Pan-genome and Genetic Variation Map for Flowering and Dwarfism Traits Completed via Genomic Analysis of 2,320 Cultivated Peanuts
Background Cultivated peanut (Arachis hypogaea) is a key legume crop supporting global edible oil and protein supplies. It holds high economic value in tropical and subtropical agriculture due to its ability to grow in dry and poor soil environments. However, it has a vulnerability of narrow genetic diversity due to its formation through natural hybridization and polyploidization among wild species. Relying solely on a single reference genome presented clear limitations in interpreting the entire complex allotetraploid structure. Existing crop research has assembled genomic sequences based on a single standard variety. This approach results in missing data issues, failing to capture genes that are lost or newly emerged between varieties, as well as large-scale structural variations (SV). In particular, despite dramatic differences among peanut varieties in key agronomic traits such as flowering cycle, pod development, and plant architecture, there was a lack of comprehensive genetic information to explain these at the molecular level. This was the background in which a genomic blueprint was needed to precisely track where useful genes are located and which variations induce phenotypes. Key Findings An international research team constructed an integrated pan-genome by performing de novo assembly of the genomes of 10 representative cultivated peanut varieties. Furthermore, they conducted whole-genome resequencing (WGRS) on 2,320 germplasm accessions collected worldwide to comprehensively survey vast genetic polymorphism. As a result of the analysis, numerous SVs, including large-scale insertions, deletions, and chromosomal inversions that were missing from the single reference genome, were revealed. Based on the pan-genome data, the researchers conducted a genome-wide association study (GWAS) to identify key trait loci directly linked to farm profitability. Notably, they identified flowering time-regulating gene loci that induce early flowering and uniform fruit set, as well as key dwarfism-related genes that inhibit stem elongation to enhance lodging resistance. Compared to previous analyses that were limited to the single nucleotide polymorphism (SNP) level, this study is notable for proving the mechanism by which large-scale structural variations directly regulate changes in gene expression levels. In strains exhibiting the dwarf phenotype, structural variations within specific regulatory regions were observed to alter the transcriptional efficiency of growth hormone signaling genes. The spectrum of 2,320 germplasm accessions clearly illustrates the flow of gene clusters that were either conserved or lost during variety differentiation. Significance and Outlook This pan-genome map will serve as a molecular accelerator for customized crop improvement in response to climate change. In modern agricultural environments where drought and high-temperature stress are becoming permanent, technologies to freely regulate flowering periods and refine plant architecture to be more compact are essential conditions for securing yields. Converting the identified dwarf loci into molecular markers can shorten the selection period for dwarf varieties by several years. Improvements in farming efficiency are also expected. Varieties with shorter, denser plant architecture are advantageous for mechanized harvesting and significantly reduce pest management costs. Additionally, by controlling flowering concentration to resolve the uneven pod development that previously occurred at different maturity stages, it becomes possible to harvest high-quality seeds with high marketability. However, challenges remain before this vast genomic data can lead directly to the commercialization of varieties. Due to the genetic redundancy characteristic of tetraploid crops, the possibility of unintended metabolic interference during the editing of specific alleles cannot be ruled out. Subsequent field trials must be conducted to empirically verify the phenotypic expression of the identified gene loci across various cultivation environments.
💡 This study provides a genetic resource navigation tool that can be directly applied to the field of molecular crop breeding. Breeders can use the 2,320-variety resequencing database to perform virtual screening of whether beneficial alleles related to flowering time and plant architecture are present when selecting breeding parents. While traditional field breeding required monitoring growth for several months after sowing to confirm flowering characteristics and dwarfism, it is now possible to identify superior individuals early through DNA chip testing at the seedling stage, increasing the rate of generational advancement by more than three times. Furthermore, it provides direct genetic coordinates for developing peanut lines optimized for smart farms—suitable for high-density cultivation and mechanized harvesting—and for breeding new varieties that maximize yield per unit area.
Nature🤖 AI summary
Europe Moves CRISPR Crops to Fields, but Farming Guidelines and Traceability Systems Must Be Established Before They Reach the Table
Background The European Union (EU) has long applied strict standards to Genetically Modified Organisms (GMOs). The regulatory guidelines established in 2001 targeted traditional transformation technologies that insert foreign genes, acting as a barrier to cultivation approval for a long time. Conversely, the sense of crisis in agriculture has intensified as climate change brings frequent droughts, heatwaves, and sudden pest outbreaks, leading to decreased productivity. Farmers have repeatedly called for the urgent development of crop varieties that can withstand abnormal weather. In response, the European Commission has embarked on revising legislation to separate new genomic technique (NGT) crops, such as those utilizing CRISPR-Cas9 gene-editing technology, from the existing GMO regulatory framework. The core of this approach involves classifying crops with fewer than 20 base modifications—changes that can also occur through natural mutation or traditional breeding—as 'Category 1,' thereby granting them significant regulatory exemptions. However, it remains to be seen whether farmers and consumers will reap tangible benefits from measures that merely lower regulatory barriers. This is because social and ecological standards have not been established for when varieties leave the laboratory and take root in actual farmland. Key Findings According to an analysis by Nature, the key factor determining the successful adoption of gene-edited crops is not the precision of the technology itself, but clear and nuanced management guidelines for implementation in the field. Even amidst the trend of deregulation, establishing a coexistence manual to prevent edited crops from mixing with conventional or organic crops was identified as the top priority. The most urgent technical issue is blocking gene flow through pollen-mediated pollination. Wind-pollinated crops with long pollen dispersal distances, such as rapeseed and maize, face the risk of edited genes flowing into adjacent organic farmlands. The analysis specifies that concrete buffer regulations, such as setting buffer zone distances, diversifying sowing periods, and restricting the sharing of harvesting equipment, must be standardized. Furthermore, to solve the technical difficulty of distinguishing natural mutations from gene-edited individuals at the molecular level, the researchers proposed mandating registration in a public database based on Digital Sequence Information (DSI). The intellectual property structure also emerged as an area requiring close review. Concerns have been raised that if a small number of multinational seed companies monopolize core patents, farmers' seed sovereignty may be diminished. Consequently, the researchers proposed an open licensing model in which a patent pool established by public agricultural research institutions provides climate-adaptive seeds to small and medium-sized breeding companies and farmers at affordable technology fees. Implications and Outlook This discussion shows that the focus of biotechnology policy has shifted from simple safety approval reviews to governance in the cultivation field. It serves as a reminder of the historical lesson that scientifically proven safety does not immediately translate into market acceptance. If gene-edited crops are distributed indiscriminately without clear farming guidelines, it is highly likely to face not only the erosion of trust in the European organic market but also a backlash of consumer opposition. The future task is the flexible implementation of systems tailored to the agricultural environment of each country. The arid climate zones of southern Spain and the plains of France and Germany have vastly different agricultural forms and ecosystem compositions. Rather than insisting on a single centralized guideline, a multi-layered management system that incorporates regional environmental risk assessments is required. Additionally, financial support measures must follow, ensuring that the costs of seed traceability verification are not passed on to farmers but are supported by public budgets. For the fruits of deregulation to lead to sustainable food production, a transparent institutional safety net must accompany precise science.
💡 Farming guidelines for gene-edited crops directly reshape business models across the seed industry and distribution chains. Specifically, farmers intending to cultivate drought-resistant wheat or pest-resistant soybeans can prevent disputes over organic certification or export rejections by securing standard operating procedures to prevent cross-contamination with adjacent farmlands. Seed distribution companies gain practical benefits by adopting digital sequence history management systems to demonstrate transparency during the seed distribution process and obtain premium sustainability certifications. Furthermore, an ecosystem will be established where small and medium-sized breeding companies can commercialize climate-tailored varieties without being blocked by the patent barriers of large agricultural corporations, simultaneously strengthening the diversity of the seed industry and food security.
Trends in plant science🤖 AI summary
Prime Editing, Rewriting Genes Without Double-Strand Breaks, Establishes a Blueprint for Precision Plant Breeding
Background Traditional CRISPR gene editing has primarily relied on cutting both strands of target DNA and relying on the cell's repair response. While effective for knocking out gene functions, precise insertion of desired sequences requires donor DNA and homology-directed repair. In plant cells, the activity of this repair pathway is low, limiting the efficiency of precise substitutions or insertions, and leaving the risk of unintended insertions or deletions at the cleavage site. Base editing can change specific bases without DNA double-strand breaks, but the types of possible substitutions and the editing range are narrow. Prime editing (PE) was developed to complement this. It combines Cas9 nickase with reverse transcriptase and uses prime editing guide RNA (pegRNA) that contains both the target location and the new sequence to be written. Theoretically, it can implement all 12 types of base substitutions, as well as short insertions and deletions, without donor DNA. The problem is that PE, which originated in mammalian cells, does not function consistently in plants. Efficiency varies greatly depending on the target locus, and even when editing occurs in somatic cells, it often fails to be transmitted to germline cells. Somatic chimerism, where different genotypes exist within a single individual, also acts as an obstacle to variety fixation. Key Findings This paper is not an experimental study testing a new editor, but a review that provides a multi-layered synthesis of accumulated PE technologies in monocots and eudicots. Rather than simply ranking the performance of different PE variants, the researchers reconstructed them into design axes: protein, pegRNA, expression regulation, DNA repair, and delivery vectors. They concluded that editing efficiency depends on the combination of these elements and the target sequence rather than any single component. The basic mechanism of PE proceeds as follows: Cas9 nickase creates a nick in one DNA strand, exposing the end to which the primer binding site of the pegRNA binds; subsequently, reverse transcriptase copies the sequence from the reverse transcription template into the DNA. Subsequently, cellular flap cleavage and mismatch repair determine whether the new sequence is established. During this process, if the length of the pegRNA primer binding site, the length and secondary structure of the reverse transcription template, additional nicking positions, or enzyme expression levels are mismatched, the editing rate can drop sharply. The paper identifies protein engineering of Cas9 and reverse transcriptase, stabilization of the 3' end of pegRNA, selection of promoters tailored to plant species and tissues, and regulation of mismatch repair pathways as major improvement strategies. However, it points out that comparing results has become difficult as various laboratories test different structures following PE1 across different crops, loci, and culture conditions. This means that optimal conditions obtained in monocots like rice cannot be directly applied to eudicots like tomato or Arabidopsis. Meaning and Prospects The next competitive advantage of PE is expected to lie in 'result predictability' rather than 'editability'. Since the performance of even the same editor varies depending on the target flanking sequences, chromatin accessibility, and the cell's repair status, standard test methods for each crop and common evaluation metrics are required. The mere fact that the desired sequence was detected in some tissues of T0 plants is insufficient. To determine whether it can be considered a real breeding resource, one must also verify the chimera ratio, byproducts, off-target editing, germline transmission rate, and stable inheritance in subsequent generations. The researchers suggest AI-based protein engineering and data-driven pegRNA design as promising solutions. The idea is to use accumulated sequence and efficiency data to select the optimal reverse transcriptase and guide structure for each target, and to design editors that increase intracellular stability and expression. Delivery technologies that reduce dependence on tissue culture must also be pursued in parallel. In major crops where regeneration is difficult, the utility of the technology decreases significantly if a complete plant cannot be obtained despite high editing efficiency. Currently, PE is less a universal breeding tool ready for immediate use in all crops and more of a platform requiring optimization for specific conditions. Nevertheless, the advantage of being able to design precise sequence changes at the level of natural variation without double-strand breaks or external donor DNA is clear. Once technical standardization and delivery issues are resolved, the focus of breeding is likely to shift from 'deleting' agricultural traits in editing to accurately 'writing' useful alleles.
💡 Seed companies can utilize PE to directly reproduce known alleles of genes involved in disease resistance, herbicide tolerance, and quality/storability into elite varieties. For example, in a lineage that has excellent yield potential but is vulnerable to a specific disease, changing just a few bases related to susceptibility could reduce the need for the lengthy process of removing unnecessary genomic regions through long-term crossing. Research institutions need a high-throughput screening system to first compare editor and pegRNA combinations by crop and target. Subsequently, to connect to commercial lines, they must evaluate not only the editing rate in T0 tissues but also the genetic stability in T1 and T2 generations, as well as chimerism and unintended byproducts. Since regulatory classifications vary by country, data proving the presence of residual foreign DNA and the molecular characteristics of the editing products must also be prepared.
Plant biotechnology journal🤖 AI summary
Development of Alfalfa with Combined Herbicide Resistance via Simultaneous Triple Gene Editing using Prime Editing
Background Alfalfa (Medicago sativa), known as the queen of forages, is a perennial legume widely cultivated as a protein source in livestock farming. It holds high value as forage due to its balanced amino acid composition and rich vitamin and mineral content. However, in packaged cultivation, it has been vulnerable to various weed invasions, facing the dual challenges of reduced yield and degraded quality. In the early growth stages, failure to compete with weeds for sunlight, moisture, and nutrients often leads to failed stand formation. The most efficient means of weed control is herbicide application. However, there has been an absolute shortage of alfalfa breeding varieties with resistance to commercial herbicides. To control both gramineous and broadleaf weeds invading single-crop fields, multiple herbicides with different modes of action must be used in combination. Existing alfalfa varieties are highly sensitive to herbicides, suffering severe injury even with slight misuse of herbicides. Even when attempting to introduce target traits, it was difficult to confer complex resistance in a short period through traditional cross-breeding due to the complex genetic structure unique to tetraploid crops. This created an urgent need for precision molecular breeding technology using gene editing. Key Findings Researchers designed a Prime Editing (PE) platform that increased expression efficiency within alfalfa cells and succeeded in simultaneously editing three target genes present in the crop genome. The target genes for editing were the acetolactate synthase genes MsALS1 and MsALS2, and the acetyl-CoA carboxylase gene MsACC1. Based on previous research results on rice homologs, mutations conferring ALS resistance to sulfonylureas and other compounds were designed into MsALS1 and MsALS2. This was intended to provide resistance to nicosulfuron, commonly used in maize and soybean cultivation. Precise point mutations were also planned for the MsACC1 gene to confer resistance to aryloxyphenoxypropionate (APP) class herbicides. To edit the three genes simultaneously in a single transformant, the researchers introduced the Csy4 nuclease system derived from bacteria for RNA processing. The principle involves expressing a multi-pegRNA transcript linked by Csy4 recognition sequences within the cell, where the Csy4 protein cleaves each RNA into individual units to form multiple complexes. Through this system, the intended base substitutions occurred precisely in the three alfalfa genes. The gene-edited alfalfa lines, in which the mutations were stably established, maintained normal growth even in greenhouse tests involving the combined application of nicosulfuron and the APP-class herbicide haloxyfop-P-methyl. Significance and Outlook This achievement, which precisely substituted three genes in a single cell without off-target deletions, is regarded as a breakthrough that has overcome the molecular breeding barrier for tetraploid perennial crops. In crops like alfalfa, which have high chromosome copy numbers and complex genetic variations, correcting with conventional gene editors that induce double-strand breaks (DSBs) often resulted in unexpected deletions or chromosomal rearrangements. This study demonstrated that by combining the PE method, which directly overwrites base sequences, with a multi-target system, it is possible to induce desired genotypes while minimizing genomic damage. At the farm level, customized control becomes possible by selectively combining graminicide (haloxyfop-P-methyl) and broadleaf/graminaceous dual-purpose herbicides (nicosulfuron). This widens the scope for implementing cross-control systems without crop damage when herbicide-resistant weeds emerge. However, there are still many challenges to overcome before reaching the packaging demonstration stage. It is necessary to determine whether foreign expression cassettes used in the transformation process persist, and measures to prevent gene flow via pollination must be established. As regulatory standards for gene-edited crops vary by country, securing null-segregant lines and verifying yield and nutritional value will determine the timeline for commercialization.
💡 This research serves as a practical catalyst for increasing productivity in large-scale alfalfa seed production complexes and commercial forage production farms. In existing alfalfa cultivation fields, the burden of labor and herbicide costs was high due to reliance on pre-plowing or limited selective herbicides for early weed control. With the introduction of the developed multi-resistance lines, herbicide combinations used in rice or maize cultivation can be flexibly applied to alfalfa fields. It can prevent the decline in crude protein content of harvested forage caused by missing the control window immediately after germination and maximize mechanized harvesting efficiency. The multiplex prime editing protocol provides a technological foundation that can be immediately applied to the molecular breeding of other crops to simultaneously improve complex agricultural traits such as drought resistance, lodging resistance, and reduced lignin content.
PNAS🤖 AI summary
Mechanism of Growth Control Without DELLA Protein Degradation Identified... CDK8-Mediated Regulation of Mediator Binding Offers New Target for Improving Crop Architecture
Background The Green Revolution of the 1960s, which dramatically increased agricultural productivity, was driven by semidwarf crops with short, sturdy stems. Thanks to these varieties, which are short-statured—making them resistant to lodging in strong winds and rain—and have high fertilizer use efficiency, global grain yields have increased explosively. At the center of this morphological change lies the DELLA protein, which blocks gibberellin (GA) signaling. DELLA proteins act as key repressors that suppress the expression of growth-promoting genes in plant cells. For a long time, the academic standard has been an 'on-off' model where GA, upon binding to its receptor, triggers the degradation of DELLA proteins via the ubiquitin-proteasome pathway. However, a binary model of either complete destruction or preservation of the protein itself has clear limitations in explaining the complex environmental changes plants face. Under various external stresses such as light, temperature, nutrient status, and pathogen invasion, plants employ strategies to precisely buffer growth rates rather than simply stopping or accelerating growth. In actual agricultural breeding, problems such as significantly reduced seed germination rates or delayed flower bud formation have persisted when DELLA genes are deleted or GA synthesis pathways are artificially blocked. Identifying an independent post-translational regulatory axis that fine-tunes transcriptional repression activity without relying on the rapid degradation of proteins has been a long-standing unresolved challenge in both plant developmental biology and crop genetics. There was an urgent need to identify a molecular switch that could finely adjust the intensity of repression without completely blocking growth. Key Findings In a study published in the September 2026 issue of the Proceedings of the National Academy of Sciences (PNAS), researchers analyzed the model plant Arabidopsis thaliana and identified that CDK8 (cyclin-dependent kinase 8), a kinase module of the Mediator complex, directly regulates DELLA protein activity. This achievement captures the fact that CDK8, known to be involved in cell cycle and basic transcriptional control, directly targets a key repressor of plant hormone responses. The researchers used a combination of biochemical analysis and mass spectrometry to prove that CDK8 specifically phosphorylates the Ser170 residue of RGA (repressor of ga1-3), a key DELLA protein in Arabidopsis. They confirmed that this phosphorylation reaction occurs not only in vitro but also in planta. The most notable result was that this phosphorylation does not induce protein degradation. Contrary to existing academic dogma, Ser170 phosphorylation did not cause significant changes in the intracellular stability, half-life, or nuclear localization of the RGA protein. Instead, it selectively weakened the physical interaction between RGA and MED15 (Mediator subunit 15), a key mediator of the transcription machinery. In other words, this reveals a mechanism whereby the transcriptional repression of downstream genes is significantly attenuated due to inhibited recruitment of the Mediator complex, even under conditions where the DELLA protein is physically maintained. Genetic validation data also clearly supported this molecular mechanism. Mutant plants with a $cdk8$ gene deletion showed slowed growth responses even when treated with GA, and exhibited defects such as delayed flowering and delayed transition from the juvenile to the adult developmental stage. When the researchers introduced a DELLA loss-of-function mutation into this $cdk8$ mutant, they observed that the delayed growth and developmental phenotypes were restored to nearly normal levels. This result clearly demonstrates that CDK8 is an essential regulator that enables normal plant developmental transitions by phosphorylating the Ser170 residue of DELLA to alleviate excessive growth inhibition. Significance and Outlook This study clearly demonstrates that plant hormone signaling possesses a flexible buffering zone through the coordination of transcriptional complex binding via phosphorylation, in addition to the extreme on-off regulation of protein degradation. It has opened a molecular pathway to selectively reduce the repression of target genes without completely eliminating growth-inhibiting proteins. Compared to the Green Revolution of the 1960s, which relied on large-scale deletions of DELLA genes or mutations that slowed protein degradation, fine-tuning via an upstream kinase regulatory axis provides a new paradigm for crop growth regulation. This achievement provides a genetic target capable of precisely controlling crop height without disrupting the physiological balance between stem elongation, seed formation, and environmental stress responses. Challenges remain before reaching industrial practical application. The CDK8 enzyme is a multifunctional kinase involved in various biological pathways beyond DELLA, such as cell division and RNA polymerase II transcriptional elongation. Therefore, there is a concern that systemic overexpression or inhibition of the CDK8 gene itself could lead to widespread metabolic disturbances or developmental abnormalities in plants. Consequently, researchers and breeders are turning their attention to a CRISPR base editing strategy that selectively corrects only the Ser170 phosphorylation motif within DELLA proteins, rather than modifying the entire enzyme. An urgent follow-up task is to confirm whether this discovery in the model plant Arabidopsis is similarly conserved in monocot grains that are staples for humanity, such as wheat, rice, barley, and maize. Subsequent large-scale empirical studies must verify the amino acid sequences of DELLA homologs in major grains and demonstrate both yield and lodging resistance in actual field environments. This marks a significant turning point in developing next-generation climate-resilient crops to ensure stable grain production amidst climate change.
💡 As climate change leads to more frequent typhoons and localized heavy rains, lodging damage—where crops fall over due to wind and rain—is identified as a factor threatening food security. The CDK8-DELLA regulatory mechanism elucidated in this study directly translates into molecular tools for precisely redesigning crop architecture in agricultural settings. The existing Green Revolution varieties had to accept losses such as reduced seed germination vigor and poor early growth during the process of reducing plant height due to DELLA deficiency. In contrast, substituting the phosphorylation target site of the DELLA protein using base editing technology can slightly attenuate mediator binding affinity while leaving the protein degradation pathway intact. A framework enabling the development of next-generation semi-dwarf wheat and rice varieties that maintain grain formation and yield intact while resisting lodging despite increased fertilizer application. This approach is also expected to be effectively applied in the development of climate-resilient crops that temporarily increase growth inhibition intensity in response to environmental stress signals such as drought or high temperatures, before recovering.
PNAS🤖 AI summary
From Rice Genomes to Single-Cell Metabolic Maps: C. Robin Buell Pioneers Crop Genomics
Background Modern crop breeding no longer stops at reading DNA sequences but has advanced to interpreting gene function and expression locations to identify useful traits. However, in the early 2000s, assembling and annotating large plant genomes remained a technical challenge due to high repeat content, complex ploidy, and frequent chromosomal mixing among different lineages. At that time, researchers struggled to determine which genomic regions corresponded to genes and what roles these genes played in yield, disease resistance, and metabolism. C. Robin Buell, a professor at the University of Georgia, as highlighted in PNAS, has been a leading plant genomicist working to bridge this gap since the dawn of DNA sequencing technology. She joined the Genome Institute in 1999 and led efforts in plant genome assembly, gene annotation, and comparative genomics. Her work has extended beyond staple crops like rice and potato to include plants such as Arabidopsis, maize, switchgrass, sweet potato, mint, and medicinal plants. In 2025, she was elected to the U.S. National Academy of Sciences for her contributions to plant genomic biology. According to the PNAS paper and NAS profile, this article is not a report of new experimental results but a profile summarizing her research trajectory and recent achievements. Key Discoveries Buell's early contributions transformed crop genomes into practical resources for researchers. She was a key member of the team that published the reference rice genome in 2005 and has maintained the rice genome annotation database for over two decades. In 2011, she also participated in the international potato genome sequencing consortium. By linking genomic assemblies with gene structure, protein function, and expression and co-expression data, she laid the foundation for identifying candidate genes for breeding. Recent research has shifted focus to rare cell types hidden within tissue averages. In the Madagascar periwinkle, which produces the anticancer compounds vinblastine and vincristine, the biosynthetic pathway is distributed across three distinct cell types. Buell's team combined chromosome-level genome and single-cell transcriptome analyses to reveal that the 38-step monoterpene indole alkaloid pathway is sequentially localized in phloem-associated parenchyma, epidermal, and idioblast cells. Analyzing whole tissues often averages out signals from rare idioblast cells, making it easy to miss candidate genes, but single-cell expression maps clearly reveal the spatial division of labor. In a follow-up study analyzing 11,321 stem cells from the tree Catharanthus roseus, the team identified 29,002 expressed genes and 23 cell clusters. Early iridoid synthase gene clusters were found concentrated in a cell population representing only 0.68% of the total plastid content. The researchers also identified MYB and bHLH transcription factors co-expressed in the same cells and proposed that the divergent transcription factor lineages used by C. roseus and the closely related Rauvolfia species reflect their evolutionary split approximately 115 million years ago. Significance and Outlook Buell's research encapsulates the trajectory of plant genomics. Starting from the early stage of reading reference genomes and annotating genes, the field has now advanced to tracking gene activation and metabolite movement within specific cell types. This approach can be applied not only to agricultural traits like yield and disease resistance but also to the design of plants for pharmaceuticals, biofuels, and biomaterials. However, genome maps alone cannot establish causal relationships for traits. Candidate genes identified in single-cell transcriptomes must be validated through gene editing, overexpression, metabolite profiling, and field trials. There is also the possibility of cell loss or stress responses during plastid isolation. Future challenges include integrating pan-genomes, spatial transcriptomes, and single-cell metabolomes to reflect structural variations and complex ploidy across varieties. Long-term maintenance and standardization of public databases will also be critical for reproducibility and breeding utility.
💡 In breeding programs, candidate genes associated with disease resistance or tuber formation can be selected from rice and potato genome databases, followed by validation in gene-edited lines and diverse cultivation environments. Narrowing the search reduces the need for random screening of large breeding populations. In the pharmaceutical and biotech industries, metabolic pathway maps of rare cells are valuable. For example, identifying transcription factors that regulate alkaloid synthesis in Madagascar periwinkle could enable their transfer to plant cell cultures or microbial production systems, offering candidates to improve the production of natural compounds with unstable supply. Connecting these findings to actual processes requires further validation of enzyme activity, intermediate toxicity, and intercellular transport mechanisms.
PNAS🤖 AI summary
Tracking the Wild Tomato Genome and Discovery of the Sl-LIP100 Gene to Restore Its Natural Flavor
Background Modern cultivated tomatoes commonly found in supermarkets have been criticized for being bland and lacking flavor compared to wild species or older varieties. This is largely due to decades of breeding efforts by plant breeders that have focused on increasing yield, extending shelf life, and enhancing resistance to pests and diseases. As a result, the genetic elements responsible for the unique natural flavor of tomatoes have gradually been lost. This has disrupted the delicate balance of sugars that provide sweetness, organic acids that contribute to tartness, and volatile compounds that determine aroma. Although research to restore flavor has been ongoing, identifying the genetic regulatory factors that control these complex metabolic pathways has remained challenging. A precise analytical approach was needed to uncover the genetic background of flavor-related compounds and to trace the superior genes from wild species that were lost during breeding. Key Findings The research team decoded the genome information of 558 tomato lines collected worldwide, including wild species, semi-domesticated varieties, and modern cultivars. They measured the levels of sugars, organic acids, and flavor-determining compounds in each line and compared them with genetic data. To detect genetic variations at the gene level with precision, they applied a genome-wide association study (GWAS). The analysis revealed the complex genetic relationships that explain how modern commercial tomatoes have lost their flavor. The team traced the accumulation pattern of deleterious alleles in wild species that negatively affect flavor as they were carried forward during domestication. This confirmed that these harmful mutations inevitably co-segregated during the selection process aimed at improving productivity. Among the newly identified genes, Sl-LIP100, which encodes a lipase enzyme, was found to be a key factor in producing the fresh tomato aroma. Experimental validation showed that this gene promotes the synthesis of five- and six-carbon volatile organic compounds (VOCs) that contribute to the characteristic green, fresh scent of tomatoes. The presence or absence of Sl-LIP100 activity was observed to cause up to a tenfold difference in the concentration of aromatic compounds within the fruit. Implications and Outlook This study marks a significant milestone by opening a concrete pathway to restore flavor without compromising yield, based on accumulated genetic data. Future research is expected to accelerate the use of molecular markers in marker-assisted breeding or the application of CRISPR gene-editing technology to remove deleterious alleles and precisely introduce beneficial alleles from wild species into cultivated varieties. In breeding programs, this will provide greater momentum for developing new tomato varieties that simultaneously achieve both flavor and productivity. However, challenges remain in fully controlling the genetic linkage drag phenomenon, where undesirable traits may be inadvertently introduced when wild species genes are incorporated. Given the complex nature of flavor, which involves interactions among multiple genes, some experts argue that flavor restoration through manipulation of a single gene may not be sufficient. The development of comprehensive genome engineering techniques that can precisely regulate sugar, acidity, and aroma in fruits is expected to be a key factor in achieving commercial success.
💡 This discovery is expected to bring tangible benefits to the food industry and smart farm growers. Consumers have increasingly preferred heirloom varieties with distinctive flavor, even at a higher price, over large, firm commercial tomatoes that lack aroma. In the future, the use of genetic markers identified in this study during early breeding stages will open the way to mass-produce commercial tomatoes with high sweetness and superior flavor. This genetic information is particularly valuable for tomatoes grown in controlled environments such as smart farms or plant factories. By combining genetic regulation with traditional methods of controlling light exposure and nutrient solutions, the enhancement of aromatic compounds can be maximized. From the grower's perspective, this can lead to higher income through the production of high-value fruits, while seed companies can secure a line of premium seeds with competitive advantages in the global market.
PNAS🤖 AI summary
Plant Growth Hormone Found to Suppress Immunity via Epigenetic Pathway, Unlocking New Key for Crop Protection
Background One of the greatest challenges plants face during growth is the efficient allocation of limited metabolic energy. When energy is concentrated to promote growth, defense becomes weakened, and conversely, when the immune system is activated, growth halts. This trade-off between growth and defense is well recognized in the scientific community, and efforts to simultaneously secure productivity and resistance have continued. A representative substance regulating plant growth is the steroid hormone brassinosteroid (BR). Similar to how animal steroids suppress inflammation and immunity in the body, it is well known that BR in plants also suppresses immune responses during growth. However, the specific control pathway has remained a mystery. The precise mechanism by which immune receptor production is inhibited at the genetic level has not been clearly elucidated. Previous studies have only observed quantitative changes in hormones or the binding of proteins, without advancing to the stage of revealing fundamental changes in genome structure. Key Findings A recent paper published in the international journal PNAS revealed the mechanism by which a specific transcription factor controls epigenetic changes and RNA processing to regulate immunity when plants receive growth signals. The research team used the model plant Arabidopsis thaliana to observe molecular-level changes induced when the BR receptor, BRASSINOSTEROID INSENSITIVE 1 (BRI1), is activated. The results were intriguing. The basic helix-loop-helix (bHLH) transcription factor CESTA (CES) and its homologous proteins, BRASSINOSTEROID ENHANCED EXPRESSION (BEE1, BEE2, BEE3), were confirmed as the main regulators of immune suppression. These transcription factors block the activity of the core immune receptor gene SUPPRESSOR OF NPR1-1 CONSTITUTIVE 1 (SNC1). Specifically, they alter the DNA methylation pattern in the genome region rich in transposable elements (TE) near the SNC1 gene, effectively changing the gene's structure to prevent its expression. In this regulatory process, CES was found to physically interact with chromatin remodeling complexes and splicing machinery within the cell. This epigenetic interaction induces alternative splicing in the pre-mRNA processing stage of SNC1. As a result, inactive variant proteins are produced instead of normal immune receptor proteins, leading to a downregulation of the plant's overall defense system. To verify the operation of this regulatory circuit, the research team conducted gene knockout experiments. They created a triple mutant (ces-tM) lacking CES, BEE1, and BEE3, and a quadruple mutant (ces-qM) with BEE2 also knocked out, and directly compared their resistance to pathogens. The mutant plants showed significantly suppressed growth but exhibited remarkably strong resistance to the oomycete pathogen Hyaloperonospora arabidopsidis (Hpa) compared to the wild type. This phenomenon is interpreted as the immune suppression switch, previously tightly locked by growth-promoting hormone signals, being released, thereby normalizing the defense capability. Implications and Prospects This study provides a detailed control map of how plants decide whether to focus on growth or allocate resources to defense in response to environmental changes. Just as steroid hormones in animals function as key suppressors of immunity in the human body, it is now clear that plants also allocate energy intelligently through epigenetic control—an evolutionary strategy for resource allocation. However, there are still obstacles to overcome before this mechanism can be directly applied in agriculture. For instance, plants with genetically modified immunity maximization showed clear growth inhibition or dwarfism compared to the wild type. Therefore, the development of a precise switch that can release immune suppression only when pathogens invade, without impairing growth, is highlighted as a key future challenge. It is proposed that subsequent research should integrate gene editing technologies or chemical regulation methods to design systems where immune proteins function normally only under specific conditions.
💡 In the modern agricultural environment, where sudden pest and disease damage is rapidly increasing due to climate change, this study provides a concrete roadmap for breeding smart crops with both high productivity and disease resistance. The application strategy is specific. For example, in cultivation regions where fungal diseases such as downy mildew frequently occur due to climate warming, a customized control scenario could be designed to temporarily halt the inhibitory effects of CES and BEE transcription factors only during the early stages of pathogen invasion. Under normal conditions, plants would grow robustly and ensure yield through the normal signaling of steroid hormones, and only in critical situations where infection is detected would methylation suppression be released to produce large amounts of immune receptors. Such a precision control system is expected to maximize the inherent immunity of crops while reducing the use of chemical pesticides, thereby laying the foundation for sustainable precision agriculture.
Journal of integrative plant biology🤖 AI summary
Induction of Complex Disease Resistance in Cucumber and Melon by Prime Editing Efficiency Exceeding 80%
Background CRISPR gene scissors technology corrects genes by randomly cutting and relying on cellular repair mechanisms, which may lead to off-target mutations. In contrast, prime editing (Prime Editing, PE) technology is gaining attention as a next-generation tool capable of precise genome modifications such as insertions, deletions, and substitutions without double-strand breaks. However, prime editing has faced limitations in dicot crops such as Cucurbitaceae and Solanaceae, where its efficiency is significantly lower. While it shows high activity in monocots like rice and wheat, major dicot crops such as cucumber, melon, and potato exhibit low editing rates, posing a barrier to practical application. To overcome these challenges, improving gene delivery systems and controlling protein expression have become urgent priorities. In particular, incomplete processing of prime editing guide RNA (pegRNA) has been identified as a primary cause of inefficiency. As the development of disease-resistant crops becomes increasingly urgent due to climate change, continuous efforts have been made to overcome the genome editing efficiency barriers in Cucurbitaceae crops. Key Findings To surpass the limitations of existing plant prime editing, the research team introduced three key optimization steps. First, spectinomycin was introduced as a selection marker, significantly improving transformation efficiency in Cucurbitaceae tissue culture. Second, the tomato elongation factor 1-alpha (SlEF1α) promoter was incorporated to maximize the expression of editing proteins. Third, a Csy4 ribonuclease (Csy4)-based self-cleavage method was integrated to ensure that pegRNAs are accurately processed according to design specifications. The resulting composite genome editing system, particularly the Csy4-PE6d model, achieved an average editing efficiency of 80.83% at target sites in cucumber. In certain gene regions, the editing success rate reached 100%. Among the transgenic lines, 36.43% exhibited homozygous editing, where both parental alleles were corrected. To confirm the scalability of this platform, the research team conducted the same experiments on melon, pumpkin, and potato cells. The results showed significant editing activity in these crops, demonstrating the potential of this system as a universal precision breeding tool. Furthermore, the team applied this technology to edit the CsSGR gene in cucumber, which is involved in aging and pathogen susceptibility. As a result, they successfully produced cucumber lines with strong resistance to bacterial angular leaf spot and downy mildew. The edited traits were stably inherited by subsequent generations. Significance and Outlook This study is significant in that it has enhanced the genome editing efficiency of Cucurbitaceae crops, which were previously considered highly challenging, and has directly led to the development of disease-resistant crops. By securing cucumber lines resistant to complex diseases, the path is now open to reduce the use of chemical pesticides and improve agricultural productivity. The combination of the tomato promoter and Csy4 is expected to expand into breeding strategies for various dicot crops in the future. This technology has the potential to become a platform for rapidly responding to pathogen mutations. Nevertheless, several tasks must be addressed before commercialization. It must be verified whether the gene scissors tool remains in the cell as an external genetic material and is completely removed by the final crop stage. A biosafety evaluation is also required to assess the impact of modified genes on the ecosystem. Additionally, harmonizing the diverse regulatory standards for genome-edited crops across countries will be a key factor in determining the pace of adoption in agriculture.
💡 The optimized prime editing platform proposed in this study has the potential to revolutionize the Cucurbitaceae crop breeding industry. Traditional breeding methods require multiple generations of crossbreeding and selection to obtain desired traits, often taking at least five to ten years. In contrast, the application of high-efficiency prime editing technology allows for the fixation of desired resistance traits through precise base editing in a single generation, significantly shortening the variety development cycle to within one to two years. In particular, seed companies are expected to be able to respond rapidly at the molecular level to new viruses and fungal diseases that are spreading quickly due to climate change. For example, the simultaneous occurrence of downy mildew and bacterial angular leaf spot due to rising temperatures can be resolved through the development of resistant lines. This will directly translate into concrete benefits for agriculture, including enhanced harvest stability and reduced economic burdens on farmers by lowering the costs of purchasing and applying chemical pesticides.
Nature🤖 AI summary
The End of Lush Forests Caused by Greenhouse Gases, Proven by 56 Million-Year-Old Plant Fossils
Background About 56 million years ago, Earth experienced an extreme warming period with temperatures rising by approximately 5 to 8 degrees Celsius due to rapid carbon emissions. Academia refers to this period as the Paleocene-Eocene Thermal Maximum (PETM) and studies it as the most analogous past case to the climate change currently faced by modern humans. A hypothesis gained traction suggesting that the high concentration of atmospheric carbon dioxide at that time acted as a fertilizer, promoting plant growth and making forests lush. However, the incomplete nature of fossil records has made it challenging to quantitatively prove the density of ancient forests. Most studies have only compared the distribution of discovered plant species. To understand the real impact of rising temperatures and water scarcity on ancient plants, a new analytical method to restore canopy density was urgently needed. Key Findings Led by Dr. Regan Dunn, a paleobotanist at the La Brea Tar Pits Museum, the research team derived answers from the fossils of ancient plant leaves. The team focused on the changes in the epidermal cell morphology of leaf fossils collected from the Hanna Basin in Wyoming. Leaves receiving more sunlight tend to have round and symmetrical epidermal cells, whereas those growing in the shade develop elongated and narrow cells to capture more light. The team devised a method to calculate the Leaf Area Index (LAI), representing the canopy density of ancient forests, by precisely analyzing the ratio of cell width to length. The results derived from this analytical method clearly demonstrated the harshness of ancient climate change. As the Paleocene-Eocene Thermal Maximum began, the canopy density of forests in the Hanna Basin area dropped sharply by about 60% compared to before. With temperatures rising by approximately 5 to 9 degrees Celsius, the once-lush forests rapidly dried up and transformed into sparse grasslands. This forest collapse did not remain a temporary phenomenon but persisted for more than 100,000 years. The extreme drought and heat stress accompanying the warming completely offset the plant growth promotion effects of increased carbon dioxide concentration. Significance and Outlook This study holds significant academic value in elucidating how temperature rise-induced water supply imbalances reduce the carbon absorption efficiency of plants. It directly refutes the optimistic expectation that increased carbon dioxide concentration will lead to more vigorous plant growth and a greener Earth. The current rate of carbon emissions by humans is about ten times faster than that of the ancient thermal maximum. Even if atmospheric carbon levels surge, if extreme heat and drought accompany it, forests may lose their ability to store carbon and are likely to become degraded. The collapse of forests could create a feedback loop by reducing carbon absorption capacity and accelerating warming. However, this analytical method is limited to fossil sites with well-preserved cuticles. The research team plans to conduct follow-up studies to verify whether ancient tropical forests and high-latitude forests also experienced similar levels of canopy collapse.
💡 The leaf area index restoration model established in this study can be directly applied to modern afforestation projects and climate model design. It has significant potential as an evaluation tool for selecting tree species with high climate change resistance in large-scale afforestation projects aimed at obtaining carbon credits. For example, introducing leaf cell analysis technology as a biological indicator to identify plants that can maintain canopy density under extreme drought and high-temperature conditions and continuously capture carbon is representative. Integrating ancient environmental data into national climate prediction systems is expected to more accurately diagnose the actual carbon absorption limits of global forests in the future.
Molecular biology reports🤖 AI summary
Post-Antibiotic Era: Non-Drug Alternatives Emerge for Livestock Disease Management, Including Gene Editing and Phage Therapy
Background Antibiotics, once hailed as powerful weapons, have become a double-edged sword, threatening human health. The rise of antimicrobial resistance (AMR) in bacteria, viruses, and fungi has rendered existing treatments ineffective, posing a global health crisis. In livestock farming, the overuse of antibiotics for productivity enhancement and disease prevention exacerbates the problem. This misuse promotes the development of resistant bacteria, which can spread through the food chain or environment, ultimately infecting humans. Projections indicate that if this trend continues, AMR will cause 10 million deaths annually worldwide by 2050. Deteriorating livestock health and increased mortality rates threaten food security. Reliance on conventional chemical antibiotics is no longer sustainable. Consequently, researchers and industry are striving to develop non-drug therapeutic alternatives to combat pathogens. Key Findings Non-drug control technologies, particularly genetic engineering, are at the forefront. CRISPR-Cas systems, a third-generation gene-editing tool, precisely targets and eliminates resistance genes in pathogens. It disrupts the genetic structure of harmful bacteria, preventing their survival and replication. Phage therapy, which selectively targets and kills specific bacteria, is also gaining prominence. Phages bind to bacterial cell walls and inject their genetic material, lysing the host cell. Unlike broad-spectrum antibiotics, phage therapy preserves beneficial gut bacteria while selectively eliminating pathogens. Probiotics and fecal microbiota transplantation (FMT) are proposed to restore microbial ecosystem balance and treat diseases. FMT involves transferring the gut microbial community from healthy individuals to other animals, establishing an immune barrier and preventing the colonization of harmful bacteria. Antimicrobial peptides (AMPs), derived from living organisms, destroy pathogen cell membranes. AMPs are considered promising alternatives to conventional antibiotics due to their lower potential for resistance development. Other potential solutions include phytotherapy using plant extracts and essential oils, nanotechnology for targeted drug delivery, biofilm disruptors that break down bacterial protective layers, and acidifiers that acidify the gut environment to inhibit the growth of harmful bacteria. Vaccination strategies and precision livestock farming (PLF) systems, which integrate information and communication technologies, are also key alternatives. PLF uses real-time sensors to monitor animal behavior and body temperature, detecting early signs of disease. This allows for early isolation or targeted treatment, preventing widespread outbreaks and reducing antibiotic use. Significance and Outlook The immediate implementation of these non-drug alternatives faces several challenges. There is a lack of sufficient basic research to demonstrate the safety and efficacy of gene-edited livestock and phage therapy. Addressing knowledge gaps and establishing rigorous biosafety standards and complex regulatory procedures are crucial for accelerating commercialization. Economic barriers also exist. Implementing precision livestock farming equipment or producing customized phage therapies requires significant initial investment and ongoing costs, which may be prohibitive for small-scale farmers. Government funding and infrastructure support are essential. Given the rapid global spread of resistant bacteria, international cooperation and harmonized regulatory standards are urgently needed. Recognizing the interconnectedness of human and animal health, integrated approaches are being actively pursued. Effective AMR management requires a One Health perspective that encompasses the environment, livestock, and humans. The development of non-drug therapies is not only about preserving livestock productivity but also about preventing a major public health disaster.
💡 The introduction of non-drug antibiotic alternatives is expected to bring about direct changes in livestock farms and the feed industry. For example, in a pig farm, a scenario could be designed where piglets with chronic diarrhea are treated by mixing phages and acidifiers into their feed. Previously, antibiotics were prescribed for short-term treatment, but now, phage therapy can protect the gut microbiome while selectively inhibiting the causative agent, E. coli. Furthermore, installing real-time monitoring cameras and sound sensors in the pigsty can detect early signs of illness, such as coughing or decreased activity. The farmer can then isolate the affected animals and administer customized plant extract essential oils and immunomodulators. This approach prevents widespread infections and ensures the supply of safe, antibiotic-free meat to consumers. This integrated management minimizes economic losses in livestock farming and creates added value by producing antibiotic-free, environmentally friendly meat.
Nature Biotechnology🤖 AI summary
Precise Insertion of 11kb Large DNA into Rice and Maize Genomes: First Implementation of the Next-Generation Plant Genome Editing Tool 'PrimeRoot'
Background Globally, there are active efforts to increase agricultural productivity and develop crops that can withstand adverse environments in response to climate change and population growth. Previously, CRISPR-Cas9 technology was mainly used to correct crop genomes. It has been effective in cutting genes or making small base changes, but it has been limited in its ability to accurately insert large genetic information of several kilobases (kb) into specific locations to significantly improve the useful traits of crops. The traditional genetically modified organism (GMO) technology, which randomly inserts foreign genes into plants, often leads to unwanted gene disruption or uneven expression. Due to the dynamic gene repair mechanisms within plant cells, the success rate of insertion is also extremely low. There is a need for a new, precise genome engineering platform that can accurately install multiple genes or large regulatory sequences into specific regions of the plant genome, which has high agricultural value. Key Findings The research team, led by Professor Caixia Gao of the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, designed PrimeRoot, a technology that can precisely transplant large amounts of DNA into desired sites in the plant genome. This editing tool is a plant-optimized Prime Editor (ePPE), which has been optimized to function efficiently in plant cells, and a system that fuses site-specific recombinases that insert external DNA in a precise direction. The ePPE first engraves a recombination enzyme recognition site at the target genome location, and then the recombination enzyme precisely merges external genetic material into this site without random replication. To verify the performance of PrimeRoot, the research team targeted the genomes of rice and maize. The results showed that they were able to precisely insert large gene sequences of up to 11.1 kilobases (kb) into the Genomic Safe Harbor (GSH) of the plant genome without any missing or off-target effects. This demonstrates that it is possible to control large-scale metabolic pathways or introduce multiple external traits into the plant genome at once, beyond simple corrections at the base level. To improve efficiency, process optimization was carried out in parallel. The research team established a sequential transformation system in which the gene editing material is injected twice at different times, rather than all at once. This new sequential method increases editing efficiency by 2 to 4 times compared to the existing method, and has laid the foundation for achieving a precise insertion efficiency of up to 8% in the genomes of rice and maize. In fact, the rice blast resistance gene pigmR and its related promoter were successfully inserted into the GSH of the rice genome, and plants with actual resistance were successfully produced. Significance and Prospects This research is expected to accelerate crop breeding and expand the field of plant synthetic biology. In the past, it was difficult to induce multiple genes involved in pest and disease resistance or adaptation to extreme climates at once with existing breeding techniques or early gene editing technologies. However, by introducing PrimeRoot, useful genes can be precisely placed at designated locations, thereby ensuring the safety and agricultural productivity of genome-edited crops. However, there are also challenges to be solved before it can be applied directly to the agricultural field. An insertion efficiency of 6% to 8% is still considered low from the perspective of industrial production, which aims for large-scale production beyond the laboratory stage. It is necessary to conduct on-farm demonstration tests to determine whether the inserted genes function properly in plants grown in various climates over the long term. It is also a major prerequisite to complete a transient expression system to reduce potential side effects caused by long-term residence in cells. This technology can be directly applied to scenarios for rapidly developing multifunctional crops that can cope with climate change. For example, a 10kb gene package containing rice blast resistance genes, drought resistance genes, and nutritional enhancement genes can be created. Then, PrimeRoot is used to insert it into a specific safe harbor in the plant genome in a single process. In the past, it took 5 to 10 years to individually cross and combine strains with each trait into a single variety, but with the new gene editing tool, it is possible to obtain seeds with multiple traits in just a few months. This opens up a practical pathway to rapidly introduce high-value crops that are resistant to pests and diseases and can withstand climate change to the market.
💡 This technology can be directly applied to scenarios for rapidly developing multifunctional crops that can cope with climate change. For example, a 10kb gene package containing rice blast resistance genes, drought resistance genes, and nutritional enhancement genes can be created. Then, PrimeRoot is used to insert it into a specific safe harbor in the plant genome in a single process. In the past, it took 5 to 10 years to individually cross and combine strains with each trait into a single variety, but with the new gene editing tool, it is possible to obtain seeds with multiple traits in just a few months. This opens up a practical pathway to rapidly introduce high-value crops that are resistant to pests and diseases and can withstand climate change to the market.
Nature🤖 AI summary
Mechanism Preserving Vigor in Sugarcane Hybrids, 'Female Restitution,' First Elucidated Through Haploid Genome Analysis
Background Sugarcane accounts for the majority of global sugar production and is also a highly valuable crop as a raw material for next-generation renewable energy sources, including bioethanol. However, due to its complex polyploid genetic structure and large genome size, genetic analysis and improvement of desirable traits have been notoriously difficult. Biotechnologists have been conducting various breeding studies to combine the beneficial genes of Saccharum officinarum, which has excellent sugar accumulation ability, with the wild species Saccharum spontaneum, which has excellent environmental stress resistance and disease resistance. One of the perplexing genetic phenomena that occurs during interspecific hybridization is female restitution, in which the maternal genome does not halve during meiosis but is passed on intact to the offspring. When this phenomenon occurs, the hybrid offspring inherit the maternal genes twice, maintaining vigor. However, the specific molecular mechanism by which the maternal chromosomes are completely preserved during meiosis and transmitted to the next generation has long remained unclear. This was because there were no genome analysis tools with sufficient resolution to individually identify the chromosomes of polyploid organisms. Key Findings A joint research team from the United States and China used haplotype-resolved F1 genomes to resolve a long-standing mystery in plant genetics. The research team traced the chromosome segregation pattern that occurs during female restitution based on a high-precision genetic map constructed from F1 individuals of two sugarcane species. The analysis revealed that the maternal chromosomes of the hybrid individuals underwent a second division restitution (SDR), in which they were duplicated, and then did not separate from each other during the second meiotic division, remaining in the same egg cell. The maternal chromosomes transmitted by this mechanism were not simply replicated. Partial genetic recombination between non-sister chromatids occurs before replication, and this recombined chromatid is then passed on intact to the offspring, and a unique signature is observed throughout the genome. The research team precisely elucidated the fine structure and sequence changes of the recombined chromatids at the molecular level using haploid decoding technology. This is a significant achievement that goes beyond previous hypotheses and clearly demonstrates the meiotic mechanism based on actual genome chromosome data. Significance and Prospects The sugarcane SDR mechanism revealed in this study is expected to have a significant impact on plant evolution research and agricultural biotechnology. By elucidating the detailed principles of female restitution, breeders can establish more systematic breeding strategies in a controlled environment to create superior varieties. The door is now open for precise genome design that efficiently combines the excellent stress resistance genes from the wild species while maintaining the high sugar content genetic pattern of the cultivated sugarcane. However, the increased sterility rate and the uncertainty of complex polyploid genetics that may accompany hybrid formation still need to be addressed. The research team plans to develop genetic tools in the future to control the recombination frequency of meiosis and arbitrarily control the natural female restitution rate.
💡 This research provides a key to addressing two critical challenges: mitigating the climate crisis and ensuring alternative energy security. Sugarcane is an essential crop for bioethanol production, which significantly contributes to carbon reduction. By integrating the excellent sugar content of cultivated sugarcane with the disease resistance and extreme drought tolerance of wild sugarcane without adverse effects, it becomes possible to extract large amounts of sugar and ethanol from even barren soils. Breeders can now control the undesirable trait segregation that occurred during random crosses in the past and create a breeding design that specifically fixes the advantages of the parent species. This shortens the variety development period by several years, helps to provide stable crops to regions where crop yields are threatened by climate change, and further enhances the feasibility of realizing a useful scenario that strengthens the global green energy supply chain.
The New phytologist🤖 AI summary
Expanding the Scope of Prime Editing in Rice from Hundreds of Base Substitutions to Thousands of Base Deletions
Background Crop traits are influenced not only by single nucleotide variations but also by sequence differences spanning tens to hundreds of nucleotides, including regulatory regions and protein domains. Replacing entire genomic regions of elite varieties with desired alleles requires large-scale homologous replacement, but achieving both efficiency and precision has been challenging in plants. Conventional CRISPR-Cas9-based homology-directed repair involves cleaving DNA double strands and supplying an external template. However, plant cells tend to prioritize non-homologous end joining, leading to insertion/deletion byproducts, and editing efficiency is significantly affected during tissue culture and plant regeneration. Prime editing (PE) utilizes Cas9 nickase, reverse transcriptase, and prime editing guide RNA (pegRNA) to introduce desired information into the target site without double-strand cleavage. However, conventional PE is typically limited to short substitutions and insertions/deletions, with significant constraints on replacing sequences longer than 100 base pairs. Key Findings The researchers expanded template-jumping prime editing (TJ-PE), a strategy reported for large DNA insertions, to homologous replacement in rice. TJ-PE is designed to allow the reverse transcriptase to continuously read the editing template, connecting the newly synthesized DNA to the opposite end of the target locus. This reduces the structural burden of conventional PE, which requires accommodating the entire long sequence within the reverse transcriptase template of a single pegRNA. In the rice genome, the researchers replaced DNA fragments of various lengths, from tens to hundreds of base pairs, with homologous sequences of the same length. The longest replaced region was 340 base pairs. The key finding is that they successfully removed the original genomic fragment and replaced it with a designed sequence of the same length, rather than simply adding nucleotides. This demonstrates the potential to move multiple variants present in natural alleles or consecutive functional motifs in a region-by-region manner. The application of TJ-PE is not limited to substitutions. The researchers precisely deleted genomic fragments of 944 to 2,024 base pairs at defined locations. Even under conditions where approximately 2,000 base pairs were removed, the highest efficiency recorded was 34.6%. As a result, it is now possible to perform both precise replacement of large fragments and kilobase-scale deletions using the same editing system. Significance and Outlook This result expands the editing scale of PE in rice from single nucleotides or short sequences to the level of gene functional regions. Alleles associated with disease resistance, environmental stress adaptation, yield, and quality often contain multiple variants clustered together. If TJ-PE can be reliably applied, it will be possible to reproduce these useful sequence clusters at once, rather than editing each variant individually. It can also be used to remove long regulatory sequences to alter gene expression or to replace regions encoding specific protein domains. However, it is difficult to assume that the maximum efficiency shown will be reproduced in all targets and varieties. Performance may vary depending on guide RNA structure, target flanking sequences, and chromatin accessibility, and the ratio of accurate substitutions to partial edits and off-target byproducts should be thoroughly verified. The stability of edited traits across generations, the stability of agronomic traits, and the evaluation of off-target variations at the whole-genome level are also important tasks to be confirmed before commercial breeding. It remains to be seen whether the technology can be extended to crops with larger genomes or higher ploidy levels, such as wheat and maize. This will be a key focus of future research.
💡 Seed companies can consider strategies to move beneficial alleles of elite varieties, associated with disease resistance or quality, from one variety to another by transferring hundreds of base pair regions, rather than recreating them base by base. For example, this could involve replacing multiple functional motifs of a promoter at once or precisely deleting an unfavorable regulatory region of approximately 2 kilobases to regulate gene expression. The fact that it precisely modifies the existing genome without randomly inserting foreign genes is also advantageous for crop development. However, in actual breeding, it is necessary to select and analyze the progeny after the editing reagents have been removed, and to confirm the absence of unintended variations and the stability of traits through whole-genome analysis and multiple generations of field trials. Given that TJ-PE efficiency is likely to vary depending on the variety and target, the development of high-efficiency guides and the standardization of plant regeneration processes will be key factors in determining the speed of industrial application.
Animals : an open access journal from MDPI🤖 AI summary
ORFV F1L-Targeted mRNA Vaccine Elicits Immune Responses Comparable to Live Vaccines
Background Contagious ecthyma, caused by orf virus (ORFV), is a highly contagious disease in sheep and goats, characterized by proliferative lesions around the lips and oral cavity. In young animals, the pain can lead to poor feeding, growth retardation, and even death. It is also a zoonotic disease that can be transmitted to humans who come into contact with infected animals. Recurrence is possible after recovery, making it difficult to eliminate the virus within a herd. Current control strategies rely primarily on commercial live vaccines. While live vaccines induce relatively strong immunity, they involve the use of live virus, which carries the risk of lesions at the injection site, transmission to unvaccinated animals, and environmental contamination. Furthermore, there are limitations in distinguishing between vaccine strains and field strains. Messenger RNA (mRNA) vaccines, on the other hand, do not involve the use of infectious viruses and allow for the rapid design of vaccine candidates by simply changing the antigen sequence. While their use has expanded in human medicine, research on vaccines for livestock animals is still in its early stages. Key Findings The researchers selected F1L, a major immunodominant surface protein of ORFV, as the antigen. mRNA encoding the F1L gene was synthesized via in vitro transcription and encapsulated in lipid nanoparticles (LNPs) to create 'F1L-mRNA-LNP'. F1L is known to induce neutralizing antibodies on the viral surface and was therefore chosen as a target to induce protective immunity without using infectious viruses. Seventy BALB/c mice were divided into five groups of 14 mice each and administered 5, 10, or 15 micrograms of F1L-mRNA-LNP, a commercial live vaccine, or phosphate-buffered saline (PBS). The primary immunization was administered by intramuscular injection, followed by a booster injection 14 days later. Immune responses were evaluated 14 days after the booster. The animal study design and reporting followed the ARRIVE 2.0 guidelines. Both the mRNA vaccine groups at all three doses and the live vaccine group showed higher F1L-specific antibody responses compared to the PBS control group. This indicates that the mRNA delivered by the LNP was translated into antigen protein in vivo and recognized by the adaptive immune system, similar to the live vaccine. Importantly, the non-replicating, single-antigen platform demonstrated immunogenicity comparable to that of the commercial live vaccine. However, this comparison is based on immune markers measured after vaccination and does not necessarily equate to 'efficacy' in the same sense as a challenge study that confirms whether it prevents ORFV infection or reduces lesions. Significance and Outlook This study demonstrates the potential to extend the mature mRNA-LNP technology used in human vaccines to infectious diseases in small ruminants. The production process does not require large-scale cultivation of ORFV, and the risk of release of live vaccine strains is reduced. If the sequence of the prevalent strain changes, it is relatively easy to replace the mRNA sequence or develop a multivalent vaccine by including other antigens, such as B2L. However, a clear limitation is that the experimental animals were mice, not the natural hosts of the disease, goats or sheep. It remains to be verified whether the antibodies neutralize the virus, whether cellular immunity and the duration of immunity are sufficient, and whether they inhibit clinical lesions and viral shedding in a challenge study with field strains. For livestock vaccines, immunogenicity is only one factor; cold chain logistics, the cost per dose, and ease of large-scale administration are also crucial for adoption. Further studies, including trials in natural hosts and cost-effective manufacturing, are needed to make it a viable alternative to live vaccines.
💡 If mRNA vaccines can be successfully implemented in goat and sheep farms, it can reduce the risk of local lesions and the spread of vaccine viruses within the farm that can occur after live vaccine administration. For example, young goats in ORFV-affected areas can be vaccinated intensively before shipment, or non-infected breeding animals can be vaccinated with a non-infectious vaccine. By combining multiple ORFV antigens or the F1L sequence of regional prevalent strains, it may be possible to develop customized multivalent vaccines for each farm. However, it is not yet possible to conclude the actual preventive effect based on the current results. Challenge studies in goats and sheep, evaluation of the duration of protective immunity, and verification of LNP stability and room temperature distribution during large-scale production are the gateways to commercialization.
Nature Genetics🤖 AI summary
Construction of a tetraploid wheat pangenome encompassing 10 subspecies… paving the way for molecular breeding to enhance yield and climate resilience
Background Wheat, a staple food crop, faces challenges in maintaining productivity due to global warming and pests. This is because the genetic diversity of cultivated wheat has been drastically reduced through thousands of years of artificial selection, leading to the loss of beneficial traits for adapting to rapid climate change. In particular, tetraploid wheat, including durum wheat, is considered difficult to improve due to its complex genetic structure. Previously, researchers have analyzed variations based on the reference genome information of a single cultivar. However, this approach has limitations in capturing broad genetic variations and differences between subgenomes. Consequently, the construction of a pangenome integrating multiple subspecies has emerged as a solution. Key Findings Creating a genomic map by integrating 12 genome datasets A joint research team from the Beijing Academy of Agricultural Sciences and the Siberian Federal Scientific and Research Center for Agro-Biotechnologies decoded 12 representative cultivars of 10 subspecies using high-quality de novo assembly techniques. Based on this, they completed a graph-based tetraploid wheat pangenome map. This research was published in the online edition of the international journal 'Nature Genetics' on July 22. Furthermore, they enhanced the research by combining the whole-genome resequencing data of 736 genetic resources collected from around the world with the pangenome map. This involved conducting a Genome-Wide Association Study (GWAS) to elucidate the correlation between traits and genetic variations using vast amounts of data. As a result, they identified an average of 250,000 structural variations per individual and demonstrated that chromosome rearrangements trigger asymmetric differentiation of subgenomes. Discovery of key genes that will be the key to crop improvement In this process, 287 gene loci associated with 32 major agricultural traits were revealed. In particular, the non-brittle rachis gene variant, which maximizes crop yield, is attracting attention. Wild wheat has a brittle rachis for reproduction, while cultivated wheat has a strong rachis, which is advantageous for human harvesting. The researchers clearly elucidated the process by which the non-brittle rachis trait was fixed through the insertion of a retrotransposon into the Btr1-A gene, leading to its loss of function. The second is the HAT14-B gene variant, which controls the number and size of wheat grains. The research team revealed that this gene encodes a specific transcription factor, and the expression level determines the yield. In fact, cultivars with large and abundant grains showed higher activity of the gene. Significance and Prospects The completed tetraploid wheat pangenome map is considered a powerful foundation for molecular breeding aimed at overcoming climate change. This is because it restores the genetic diversity of wild subspecies that have survived in harsh environments. As a result, it is now possible to accurately identify genes specialized for drought and high temperatures and apply them to crop improvement. The scenario of introducing immune traits from wild species to develop cultivars resistant to climate stress has become even more concrete. However, there are limitations in developing actual new crop varieties using pangenome information. This is because it is necessary to demonstrate that the target traits are expressed in the same way in the complex interaction with environmental factors. It is also necessary to overcome the technical challenges of correcting target sites using CRISPR gene editing. The research team plans to dedicate itself to expanding the pangenome research of hexaploid bread wheat in the future, based on this data.
💡 This pangenome map is planned to be used as a useful compass for the agricultural and food industries to shorten the cycle of developing new cultivars. A typical application scenario is the design of customized wheat cultivars suitable for regions experiencing severe drought, such as Africa and the Middle East. By utilizing the information of the 287 gene loci and alleles discovered by the researchers, it is possible to shorten the breeding period for drought-resistant cultivars from more than 10 years with conventional breeding methods to within 3-4 years using Marker-Assisted Selection (MAS) technology. In addition, it is expected that the early introduction of wheat with enhanced immunity and pest resistance will reduce the use of pesticides and fertilizers, thereby preventing environmental pollution and reducing production costs. A practical means of overcoming the food crisis has been 마련된 셈이다.
Nature Genetics🤖 AI summary
Discovery of Keys to Enhanced Yield from Wild Wheat Genome: Completion of a Tetraploid Wheat Pangenome Map Covering 10 Subspecies
Background Wheat Genome Complexity: A Challenge in the Face of the Climate Crisis and Global Food Security Wheat is a staple crop that provides approximately 20% of the world's calorie intake. With the urgent need to dramatically improve agricultural productivity in the face of climate change and population growth, the complex wheat genome presents significant research challenges. Modern bread wheat, a tetraploid wheat, is derived from two distinct subgenomes. The Necessity of Pangenomes to Overcome the Limitations of Single Reference Genomes Previously, research has relied on single reference genomes derived from individual varieties. However, this approach fails to fully capture the genomic diversity observed across different varieties. To achieve improvements in crop productivity and enhance climate resilience, the construction of a pangenome, which encompasses the genetic information of multiple subspecies, is essential. Key Findings Tetraploid Wheat Graph-Based Pangenome Constructed from 12 Genomes The researchers decoded the genomes of 12 tetraploid wheat varieties, representing 10 subspecies, and constructed the first graph-based pangenome for tetraploid wheat. The analysis revealed that chromosomal rearrangements are a major factor driving asymmetry and genetic differentiation between subgenomes. The researchers identified an average of 250,000 structural variations (SVs) per variety, most of which were found to be caused by the activity of transposable elements (TEs). Identification of Molecular Keys Regulating Reduced Shattering and Increased Grain Size Furthermore, a population genomic analysis of 736 varieties worldwide revealed distinct subgroups adapted to local environments. The study successfully elucidated the mechanism behind 'non-brittle rachis,' a key trait that emerged during the domestication of wild wheat. The researchers identified a new allele that maximizes yield by inactivating the Btr1-A gene, which is responsible for non-brittle rachis, through the insertion of a specific retrotransposon. In addition, a genome-wide association study (GWAS) identified 287 genetic regions associated with 32 agronomic traits. Among these, the HAT14-B gene, a transcription factor (TF) located on chromosome 15, was found to contribute to increased productivity by simultaneously increasing grain size and the number of spikelets per spike. Significance and Prospects A Foundation for Developing Customized Wheat Varieties to Address the Climate Crisis The newly constructed tetraploid wheat pangenome provides a new breakthrough for modern breeding, which aims to improve agricultural productivity. By restoring useful genetic diversity that was not accessible with a single reference genome, it will be possible to develop customized crops that are resistant to climate change, such as drought and high temperatures. From Pasta to Bread: A New Horizon for Food Security However, there are still challenges to be addressed before the research findings can be implemented in actual cultivation. Large-scale field trials are needed to verify whether the identified beneficial genes are stably expressed under various environmental conditions. Furthermore, technical support software is needed to integrate this complex genomic information into actual breeding programs.
💡 This research presents a concrete scenario for addressing the climate crisis and developing customized, high-value crops. For example, drought-resistant SVs from wild species adapted to arid climates can be tracked in the pangenome database and used as molecular markers. In addition, the researchers have attempted to develop a super-productive durum wheat variety for pasta by using CRISPR to fine-tune the HAT14-B gene, increasing grain size while maximizing the number of grains per spike. These research findings can also be cross-applied to improve bread wheat varieties, and are expected to directly provide gene-based breeding solutions to the global seed industry.
Nature Genetics🤖 AI summary
Discovery of an Atypical Protein Barrier that Prevents Chromatin Penetration, Maintaining Genome Stability and Increasing Crop Yield
Background The chromosomes of living organisms, which contain genetic information, are controlled by a highly precise regulatory system. Demethylases, enzymes that remove methyl groups (Methyl group) attached to DNA or RNA, are key molecules that regulate gene activation. If these enzymes lose control and indiscriminately activate any region of the genome, it can lead to fatal diseases such as cancer, and genomic instability will also increase significantly. Previously, the biological community believed that intrinsically disordered regions (IDRs), which are proteins with no fixed three-dimensional structure, mainly induce phase separation and act as promoters to help gene expression. However, it has not been revealed that this flexible structure actually plays a role as a brake that limits the excessive access of enzymes to chromatin. Key Findings The research team led by Professor Chuan He at the University of Chicago questioned why FTO and ALKBH5, representative RNA demethylases, have similar active sites but different mechanisms of action. The research team precisely observed the molecular behavior of the two enzymes using protein binding analysis and gene sequencing techniques. The analysis revealed that the IDR located at the C-terminus of ALKBH5 acts as a physical anchor that binds the enzyme to messenger RNA (mRNA). The researchers explained that this device physically limits the binding of the enzyme to chromatin, thereby preserving the stability of the genome inside the cell. The research team designed an experiment to remove the C-terminal IDR of ALKBH5 using a mammalian cell model. The enzyme, which lost its inhibitory device, showed a pattern of immediately moving from mRNA to chromatin-associated RNA (caRNA). The removal of this barrier resulted in opening the chromatin structure and stimulating gene transcription activation. Furthermore, the research team turned their attention to plant research. They induced mutants by transplanting a nuclear localization signal (NLS) into ALKBH5 homologs of Arabidopsis and Rice and removing specific IDR regions. As a result, it was observed that the expression of genes that regulate photosynthesis and growth was accelerated in the mutant plants, and the root development was accelerated, resulting in a significant increase in yield and biomass compared to the control group. The researchers added that this inhibitory mechanism is conserved in various chromatin-modifying proteins, such as histone demethylase, and prevents the abnormal activation of transposable elements. Significance and Prospects This research overturned the long-held belief in the academic community that flexible, intrinsically disordered structures only promote protein activity. It proved that IDRs can actually function as molecular brakes that control the spatial arrangement of enzymes and regulate chromatin binding. This is considered to be a strategy that living organisms have evolutionarily selected to prevent indiscriminate activation of the entire genome and maintain stability. The academic community expects that this research will open a new path for crop improvement. By finely adjusting the genetic brakes that plants use to inhibit their own growth, it will be possible to develop new varieties that can respond to climate change and food crises. However, the long-term impact of artificially removing IDRs on the overall stability of the genome has not yet been verified. Rapid gene activation may cause unexpected side effects on the plant's lifespan or resistance to diseases and pests, so comprehensive safety verification is required.
💡 This research has the potential to contribute directly to the agricultural sector and increase the income of farmers. A representative application scenario is to precisely correct the IDR sequence of the ALKBH5 gene in crops using the CRISPR gene editing technique without introducing external genes. This technology is classified as a gene-edited crop and is expected to significantly shorten the safety assessment period compared to existing genetically modified crops (GMOs). By applying this to areas facing food crises and distributing rice or wheat varieties that can grow roots widely and quickly even in poor soil, it can greatly contribute to solving the food shortage. The inhibitory mechanism revealed in animal cells is also a useful target in the medical and pharmaceutical industries. By targeting cancer cells in which cancer genes are indiscriminately activated due to the overactivation of FTO or ALKBH5, and administering small molecule compounds that mimic the IDR brake, it is predicted that a new drug development pathway will be opened to inhibit tumor growth.
Nature Genetics🤖 AI summary
A pangenome map of 125 cucumber varieties reveals the secrets of disease resistance and fruit length evolution
Background Existing crop genome studies have tended to rely heavily on reference genomes of single varieties. However, it is realistically difficult for a single standard genome alone to perfectly reflect the genetic diversity among individuals. In particular, the popular Single Nucleotide Polymorphism (SNP) analysis method is useful for identifying micro-variations, but it has limitations in detecting structural variations (SVs) where thousands of base pairs are swapped. Cucumber, originating in India, has spread around the world, and traits such as fruit length and disease resistance have diversified in response to the climate. Breeders aim to maximize genetic potential and develop superior new varieties. However, the genomic map that identifies the key variations that cause trait changes has long been shrouded in mystery. As the need arises to integrate the genetic information of all cucumber varieties in order to respond agilely to climate change and emerging pests and diseases, the time has come for a massive gene map. Key Findings The Vegetable and Flower Research Institute of the Chinese Academy of Agricultural Sciences (CAAS) and Qingdao Agricultural University jointly conducted a study to address this issue, performing precise genetic analysis on 125 cucumber varieties. The research team completed chromosome-level genome assemblies for each variety and successfully constructed a large-scale, graph-based pangenome by organically linking them. The high-confidence SVs identified by this pangenome map totaled 171,892. Furthermore, the researchers boldly attempted a Genome-Wide Association Study (GWAS) based on SVs, targeting 38 key agricultural traits of cucumber. The analysis revealed that more than 60% of the overall genetic signals were SV-specific association signals that could not be detected by existing SNP analysis methods. This is considered to have maximized the interpretability of genetic diversity in the genetic variation analysis model. With this genomic map, the research team successfully discovered key genes that have long been a challenge for breeders. A notable achievement is the gene cloning of 'CsCcu', a cucumber black spot resistance gene. This resistance gene was previously in a state of loss due to variation in the single reference genome, but the gene location and sequence were finally restored by precisely tracing back the pangenome graph. The research team also focused on identifying the causative variations that determine cucumber fruit length. The analysis revealed that a specific Long Terminal Repeat (LTR) transposon inserted in the first exon region of 'CsSPL1', a plant growth regulation gene, acts as a positive regulator that increases cucumber fruit length. Cucumbers with this LTR transposon have long fruits, which explains the preference differences and breeding path divergence between short cucumbers in Eurasia and long cucumbers in East Asia. Significance and Prospects The graph pangenome map constructed in this study is attracting attention as an asset that will change the paradigm of crop genome research. It now provides the foundation for molecular design breeding, which can artificially control commercially valuable complex traits such as specific pathogen resistance or fruit length. In the past, conventional breeding methods were passive, waiting for traits to be expressed over several generations after cross-breeding. Pangenome-based molecular design can be defined as an engineering process that precisely targets and assembles target genes. However, there are still technical hurdles to overcome before these genetic variations can be applied to commercially cultivable common cucumber varieties. In the process of introducing excellent genes from wild species into cultivated species, unexpected trait changes, such as growth reduction or taste changes, are often observed. The precise working mechanism of the multi-gene network that responds to climate change has not yet been fully elucidated. The research team expresses its intention to combine artificial intelligence (AI) technology and integrated biological analysis methods in the future to elucidate this complex genetic association.
💡 This pangenome information provides direct solutions for the agricultural sector and the seed industry. In the past, it took 7-10 years to fix useful traits in conventional cucumber breeding, but the introduction of the newly developed SV-based genetic markers has drastically reduced the breeding period to 3-5 years. A typical application scenario is the selection of black spot-resistant individuals. Seed companies use SV markers around the newly discovered 'CsCcu' gene to accurately screen for resistant individuals at the seedling stage. In addition, when developing long cucumbers for the East Asian market, the LTR insertion in the 'CsSPL1' gene can be checked using a gene chip to control fruit length. As a result, producers will benefit from a significant reduction in pesticide costs for pest and disease control. Breeders are also expected to strengthen their export competitiveness in the global market by designing cucumber new varieties tailored to market demand.

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