Developing an SNP dataset for efficiently evaluating soybean germplasm resources using the genome sequencing data of 3,661 soybean accessions.

BACKGROUND: Single nucleotide polymorphism (SNP) markers play significant roles in accelerating breeding and basic crop research. Several soybean SNP panels have been developed. However, there is still a lack of SNP panels for differentiating between wild and cultivated populations, as well as for detecting polymorphisms within both wild and cultivated populations. RESULTS: This study utilized publicly available resequencing data from over 3,000 soybean accessions to identify differentiating and highly conserved SNP and insertion/deletion (InDel) markers between wild and cultivated soybean populations. Additionally, a naturally occurring mutant gene library was constructed by analyzing large-effect SNPs and InDels in the population. CONCLUSION: The markers obtained in this study are associated with numerous genes governing agronomic traits, thus facilitating the evaluation of soybean germplasms and the efficient differentiation between wild and cultivated soybeans. The natural mutant gene library permits the quick identification of individuals with natural mutations in functional genes, providing convenience for accelerating soybean breeding using reverse genetics.

MicroRNA 4407 modulates nodulation in soybean by repressing a root-specific ISOPENTENYLTRANSFERASE (GmIPT3).

MicroRNAs (miRNAs) are important regulators of plant biological processes, including soybean nodulation. One miRNA, miR4407, was identified in soybean roots and nodules. However, the function of miR4407 in soybean is still unknown. MiR4407, unique to soybean, positively regulates lateral root emergence and root structures and represses a root-specific ISOPENTENYLTRANSFERASE (GmIPT3). By altering the expression of miR4407 and GmIPT3, we investigated the role of miR4407 in lateral root and nodule development. Both miR4407 and GmIPT3 are expressed in the inner root cortex and nodule primordia. Upon rhizobial inoculation, miR4407 was downregulated while GmIPT3 was upregulated. Overexpressing miR4407 reduced the number of nodules in transgenic soybean hairy roots while overexpressing the wild-type GmIPT3 or a miR4407-resistant GmIPT3 mutant (mGmIPT3) significantly increased the nodule number. The mechanism of miR4407 and GmIPT3 functions was also linked to autoregulation of nodulation (AON), where miR4407 overexpression repressed miR172c and activated its target, GmNNC1, turning on AON. Exogenous CK mimicked the effects of GmIPT3 overexpression on miR172c, supporting the notion that GmIPT3 regulates nodulation by enhancing root-derived CK. Overall, our data revealed a new miRNA-mediated regulatory mechanism of nodulation in soybean. MiR4407 showed a dual role in lateral root and nodule development.

A natural non-synonymous single nucleotide polymorphism in GmbHLH113 negates its inhibitory effect on root hair elongation in soybean.

Root hair length (RHL) is an important character that affects nutrient acquisition in plants. The regulatory network in soybean controlling RHL is yet to be fully understood. In this study, we identified a quantitative trait locus (QTL) regulating RHL. One candidate causal gene in this QTL (GmbHLH113), preferentially expressed in root hairs, was annotated as encoding a basic helix-loop-helix transcription factor. In wild soybeans, the allelic type of GmbHLH113 with a glycine in the 13th residue, which was associated with a reduction in RHL, was shown to localize in the nucleus and activate gene transcription. Another allelic type with a single nucleotide polymorphism that resulted in a glutamate in the 13th residue is fixed in cultivated soybeans, and it lost the ability to localize to the nucleus or negatively regulate RHL. The ectopic expression of GmbHLH113 from W05 in Arabidopsis root hairs resulted in shorter RHL and reduced phosphorus (P) accumulation in shoots. Hence, a loss-of-function allele in cultivated soybeans might have been selected during domestication due to its association with a longer RHL and improved nutrient acquisition.

QTL analyses of soybean root system architecture revealed genetic relationships with shoot-related traits.

KEY MESSAGE: The genetic basis of soybean root system architecture (RSA) and the genetic relationship between shoot and RSA were revealed by integrating data from recombinant inbred population grafting and QTL mapping. Variations in root system architecture (RSA) affect the functions of roots and thus play vital roles in plant adaptations and agricultural productivity. The aim of this study was to unravel the genetic relationship between RSA traits and shoot-related traits in soybean. This study characterized RSA variability at seedling stage in a recombinant inbred population, derived from a cross between cultivated soybean C08 and wild soybean W05, and performed high-resolution quantitative trait locus (QTL) mapping. In total, 34 and 41 QTLs were detected for RSA-related and shoot-related traits, respectively, constituting eight QTL clusters. Significant QTL correspondence was found between shoot biomass and RSA-related traits, consistent with significant correlations between these phenotypes. RSA-related QTLs also overlapped with selection regions in the genome, suggesting the cultivar RSA could be a partial consequence of domestication. Using reciprocal grafting, we confirmed that shoot-derived signals affected root development and the effects were controlled by multiple loci. Meanwhile, RSA-related QTLs were found to co-localize with four soybean flowering-time loci. Consistent with the phenotypes of the parental lines of our RI population, diminishing the function of flowering controlling E1 family through RNA interference (RNAi) led to reduced root growth. This implies that the flowering time-related genes within the RSA-related QTLs are actually contributing to RSA. To conclude, this study identified the QTLs that determine RSA through controlling root growth indirectly via regulating shoot functions, and discovered superior alleles from wild soybean that could be used to improve the root structure in existing soybean cultivars.

Priming-induced alterations in histone modifications modulate transcriptional responses in soybean under salt stress.

Plants that have experienced certain abiotic stress may gain tolerance to a similar stress in subsequent exposure. This phenomenon, called priming, was observed here in soybean (Glycine max) seedlings exposed to salt stress. Time-course transcriptomic profiles revealed distinctively different transcriptional responses in the primed seedlings from those in the non-primed seedlings under high salinity stress, indicating a stress response strategy of repressing unhelpful biotic stress responses and focusing on the promotion of those responses important for salt tolerance. To identify histone marks altered by the priming salinity treatment, a genome-wide profiling of histone 3 lysine 4 dimethylation (H3K4me2), H3K4me3, and histone 3 lysine 9 acetylation (H3K9ac) was performed. Our integrative analyses revealed that priming induced drastic alterations in these histone marks, which coordinately modified the stress response, ion homeostasis, and cell wall modification. Furthermore, transcriptional network analyses unveiled epigenetically modified networks which mediate the strategic downregulation of defense responses. Altering the histone acetylation status using a chemical inhibitor could elicit the priming-like transcriptional responses in non-primed seedlings, confirming the importance of histone marks in forming the priming response.

Increased copy number of gibberellin 2-oxidase 8 genes reduced trailing growth and shoot length during soybean domestication.

Copy number variations (CNVs) play important roles in crop domestication. However, there is only very limited information on the involvement of CNVs in soybean domestication. Trailing growth and long shoots are soybean adaptations for natural habitats but cause lodging that hampers yield in cultivation. Previous studies have focused on Dt1/2 affecting the indeterminate/determinate growth habit, whereas the possible role of the gibberellin pathway remained unclear. In the present study, quantitative trait locus (QTL) mapping of a recombinant inbred population of 460 lines revealed a trailing-growth-and-shoot-length QTL. A CNV region within this QTL was identified, featuring the apical bud-expressed gibberellin 2-oxidase 8A/B, the copy numbers of which were positively correlated with expression levels and negatively with trailing growth and shoot length, and their effects were demonstrated by transgenic soybean and Arabidopsis thaliana. Based on the fixation index, this CNV region underwent intense selection during the initial domestication process.

Drivers of carbon flux in drip irrigation maize fields in northwest China.

BACKGROUND: Under the escalating threat to sustainable development from the global increase in carbon dioxide concentrations, the variations in carbon flux in the farmland ecosystem and their influencing factors have attracted global attention. Over the past few decades, with the development of eddy covariance technology, the carbon fluxes of farmlands have been determined in many countries. However, studies are very limited for drip irrigation maize the arid regions in northwestern China, which covers a large area where a mixed mode of agriculture and grazing is practiced. RESULTS: To study the effects of drip irrigation on the net ecosystem productivity (NEE), ecosystem respiration (ER), gross primary production (GPP) and net biome productivity (NBP) in the arid regions of northwestern China, we measured the carbon flux annually from 2014 to 2018 using an eddy covariance system. Our results showed that the maize field carbon flux exhibited single-peak seasonal patterns during the growing seasons. During 2014-2018, the NEE, ER and GPP of the drip-irrigated maize field ranged between - 407 ~ - 729 g C m-2, 485.46 ~ 975.46 g C m-2, and 1068.23 ~ 1705.30 g C m-2. In four of the 5 study years, the ER released back to the atmosphere was just over half of the carbon fixed by photosynthesis. The mean daily NEE, ER and GPP were significantly correlated with the net radiation (Rn), air temperature (Ta), leaf area index (LAI) and soil moisture (SWC). The results of path analysis showed that leaf area index is the main driving force of seasonal variation of carbon flux. When harvested removals were considered, the annual NBP was - 234 g C m-2, and the drip-irrigated maize field was a carbon source. CONCLUSIONS: This study shows the variation and influencing factors of NEE, ER and GPP in the growth period of spring maize under film drip irrigation in arid areas of northwest China. The ecosystem was a carbon sink before maize harvest, but it was converted into a carbon source considering the carbon emissions after harvest. The variation of carbon flux was influenced by both environmental and vegetation factors, and its leaf area index was the main driver that affects the seasonal variation of carbon flux.

The soybean plasma membrane-localized cation/H+ exchanger GmCHX20a plays a negative role under salt stress.

Cation/H+ -exchanger (CHX) perform diverse functions in plants, including being a part of the protective mechanisms to cope with salt stress. GmCHX1 has been previously identified as the causal gene in a major salt-tolerance quantitative trait locus (QTL) in soybean, but little is known about another close paralog, GmCHX20a, found in the same QTL. In this study, GmCHX20a was characterized along with GmCHX1. The expression patterns of the two genes and the direction of Na+ flux directed by overexpression of these two transporters are different, suggesting that they are functionally distinct. The ectopic expression of GmCHX20a led to an increase in salt sensitivity and osmotic tolerance, which was consistent with its role in increasing Na+ uptake into the root. Although this seems counter-intuitive, it may in fact be part of the mechanism by which soybean could counter act the effects of osmotic stress, which is commonly manifested in the initial stage of salinity stress. On the other hand, GmCHX1 from salt-tolerant soybean was shown to protect plants via Na+ exclusion under salt stress. Taken together these results suggest that GmCHX20a and GmCHX1 might work complementally through a concerted effort to address both osmotic stress and ionic stress as a result of elevated salinity.

Photodynamic therapy on prostate cancer cells involve mitochondria membrane proteins.

OBJECTIVE: Photodynamic therapy for prostate cancer has emerged, however the evaluation of its mechanism of action has not yet been clarified. This study aims to explore the mechanism and significance of photodynamic therapy on prostate cancer in vitro. METHODS: Cultured prostate cancer cells were divided into two groups: untreated and photodynamic therapy treatment. The protein of each group was extracted and analyzed by MALDI-TOF/MSMS method. The significantly expressed proteins were identified in the NCBI human protein database. The change of mitochondrial membrane permeability after photodynamic treatment was examined by transmission electron microscopy. RESULTS: The total protein content and band distribution of photodynamic treatment group were similar to the control group. Two mitochondrial membrane proteins were down-regulated significantly. They are mitochondrial heat shock protein (HSP60) (Entrez Gene ID: 31542947, PI 5.7, MW: 61016.4, Protein Score: 354, Protein Score C.I.%:100), and voltage-dependent anion channel (VDAC) (Entrez Gene ID: 340201, PI 7.49, MW: 31574.6, Protein Score: 178, Protein Score C.I.%:100). Transmission electron microscopy showed the loss of integrity of mitochondrial membranes. CONCLUSIONS: Photodynamic therapy changes mitochondrial membrane permeability, leading to the eventual death of cancer cells. The regulation of proteins related to mitochondrial membrane permeability may become an indicator of the efficacy of photodynamic therapy.

Analysis of Soybean Long Non-Coding RNAs Reveals a Subset of Small Peptide-Coding Transcripts.

Long non-coding RNAs (lncRNAs) are defined as non-protein-coding transcripts that are at least 200 nucleotides long. They are known to play pivotal roles in regulating gene expression, especially during stress responses in plants. We used a large collection of in-house transcriptome data from various soybean (Glycine max and Glycine soja) tissues treated under different conditions to perform a comprehensive identification of soybean lncRNAs. We also retrieved publicly available soybean transcriptome data that were of sufficient quality and sequencing depth to enrich our analysis. In total, RNA-sequencing data of 332 samples were used for this analysis. An integrated reference-based, de novo transcript assembly was developed that identified ∼69,000 lncRNA gene loci. We showed that lncRNAs are distinct from both protein-coding transcripts and genomic background noise in terms of length, number of exons, transposable element composition, and sequence conservation level across legume species. The tissue-specific and time-specific transcriptional responses of the lncRNA genes under some stress conditions may suggest their biological relevance. The transcription start sites of lncRNA gene loci tend to be close to their nearest protein-coding genes, and they may be transcriptionally related to the protein-coding genes, particularly for antisense and intronic lncRNAs. A previously unreported subset of small peptide-coding transcripts was identified from these lncRNA loci via tandem mass spectrometry, which paved the way for investigating their functional roles. Our results also highlight the present inadequacy of the bioinformatic definition of lncRNA, which excludes those lncRNA gene loci with small open reading frames from being regarded as protein-coding.

Impacts of genomic research on soybean improvement in East Asia.

It has been commonly accepted that soybean domestication originated in East Asia. Although East Asia has the historical merit in soybean production, the USA has become the top soybean producer in the world since 1950s. Following that, Brazil and Argentina have been the major soybean producers since 1970s and 1990s, respectively. China has once been the exporter of soybean to Japan before 1990s, yet she became a net soybean importer as Japan and the Republic of Korea do. Furthermore, the soybean yield per unit area in East Asia has stagnated during the past decade. To improve soybean production and enhance food security in these East Asian countries, much investment has been made, especially in the breeding of better performing soybean germplasms. As a result, China, Japan, and the Republic of Korea have become three important centers for soybean genomic research. With new technologies, the rate and precision of the identification of important genomic loci associated with desired traits from germplasm collections or mutants have increased significantly. Genome editing on soybean is also becoming more established. The year 2019 marked a new era for crop genome editing in the commercialization of the first genome-edited plant product, which is a high-oleic-acid soybean oil. In this review, we have summarized the latest developments in soybean breeding technologies and the remarkable progress in soybean breeding-related research in China, Japan, and the Republic of Korea.

High-Throughput Mass Spectrometric Analysis of the Whole Proteome and Secretome From Sinorhizobium fredii Strains CCBAU25509 and CCBAU45436.

Sinorhizobium fredii is a dominant rhizobium on alkaline-saline land that can induce nitrogen-fixing symbiotic root nodules in soybean. Two S. fredii strains, CCBAU25509 and CCBAU45436, were used in this study to facilitate in-depth analyses of this species and its interactions with soybean. We have previously completed the full assembly of the genomes and detailed transcriptomic analyses for these two S. fredii strains, CCBAU25509 and CCBAU45436, that exhibit differential compatibility toward some soybean hosts. In this work, we performed high-throughput Orbitrap analyses of the whole proteomes and secretomes of CCBAU25509 and CCBAU45436 at different growth stages. Our proteomic data cover coding sequences in the chromosome, chromid, symbiotic plasmid, and other accessory plasmids. In general, we found higher levels of protein expression by genes in the chromosomal genome, whereas proteins encoded by the symbiotic plasmid were differentially accumulated in bacteroids. We identified secreted proteins from the extracellular medium, including seven and eight Nodulation Outer Proteins (Nops) encoded by the symbiotic plasmid of CCBAU25509 and CCBAU45436, respectively. Differential host restriction of CCBAU25509 and CCBAU45436 is regulated by the allelic type of the soybean Rj2(Rfg1) protein. Using sequencing data from this work and available in public databases, our analysis confirmed that the soybean Rj2(Rfg1) protein has three major allelic types (Rj2/rfg1, rj2/Rfg1, rj2/rfg1) that determine the host restriction of some Bradyrhizobium diazoefficiens and S. fredii strains. A mutant defective in the type 3 protein secretion system (T3SS) in CCBAU25509 allowed this strain to nodulate otherwise-incompatible soybeans carrying the rj2/Rfg1 allelic type, probably by disrupting Nops secretion. The allelic forms of NopP and NopI in S. fredii might be associated with the restriction imposed by Rfg1. By swapping the NopP between CCBAU25509 and CCBAU45436, we found that only the strains carrying NopP from CCBAU45436 could nodulate soybeans carrying the rj2/Rfg1 allelic type. However, no direct interaction between either forms of NopP and Rfg1 could be observed.

A reference-grade wild soybean genome.

Efficient crop improvement depends on the application of accurate genetic information contained in diverse germplasm resources. Here we report a reference-grade genome of wild soybean accession W05, with a final assembled genome size of 1013.2 Mb and a contig N50 of 3.3 Mb. The analytical power of the W05 genome is demonstrated by several examples. First, we identify an inversion at the locus determining seed coat color during domestication. Second, a translocation event between chromosomes 11 and 13 of some genotypes is shown to interfere with the assignment of QTLs. Third, we find a region containing copy number variations of the Kunitz trypsin inhibitor (KTI) genes. Such findings illustrate the power of this assembly in the analysis of large structural variations in soybean germplasm collections. The wild soybean genome assembly has wide applications in comparative genomic and evolutionary studies, as well as in crop breeding and improvement programs.

Transcriptomic reprogramming in soybean seedlings under salt stress.

To obtain a comprehensive understanding of transcriptomic reprogramming under salt stress, we performed whole-transcriptome sequencing on the leaf and root of soybean seedlings subjected to salt treatment in a time-course experiment (0, 1, 2, 4, 24, and 48 hr). This time series dataset enabled us to identify important hubs and connections of gene expressions. We highlighted the analysis on phytohormone signaling pathways and their possible crosstalks. Differential expressions were also found among those genes involved in carbon and nitrogen metabolism. In general, the salt-treated seedlings slowed down their photosynthetic functions and ramped up sugar catabolism to provide extra energy for survival. Primary nitrogen assimilation was shut down whereas nitrogen resources were redistributed. Overall, the results from the transcriptomic analyses indicate that the plant uses a multipronged approach to overcome salt stress, with both fast-acting, immediate physiological responses, and longer term reactions that may involve metabolic adjustment.

Modelling predicts that soybean is poised to dominate crop production across Africa.

The superior agronomic and human nutritional properties of grain legumes (pulses) make them an ideal foundation for future sustainable agriculture. Legume-based farming is particularly important in Africa, where small-scale agricultural systems dominate the food production landscape. Legumes provide an inexpensive source of protein and nutrients to African households as well as natural fertilization for the soil. Although the consumption of traditionally grown legumes has started to decline, the production of soybeans (Glycine max Merr.) is spreading fast, especially across southern Africa. Predictions of future land-use allocation and production show that the soybean is poised to dominate future production across Africa. Land use models project an expansion of harvest area, whereas crop models project possible yield increases. Moreover, a seed change in farming strategy is underway. This is being driven largely by the combined cash crop value of products such as oils and the high nutritional benefits of soybean as an animal feed. Intensification of soybean production has the potential to reduce the dependence of Africa on soybean imports. However, a successful "soybean bonanza" across Africa necessitates an intensive research, development, extension, and policy agenda to ensure that soybean genetic improvements and production technology meet future demands for sustainable production.

Proteomic analysis reveals that pheophorbide a-mediated photodynamic treatment inhibits prostate cancer growth by hampering GDP-GTP exchange of ras-family proteins.

BACKGROUND: We previously reported that pheophorbide a (PhA), excited by 630 nm light, significantly inhibited the growth of prostate cancer cells. In this study, we employed whole-cell proteomics to investigate photodynamic treatment (PDT)-related proteins. METHODS: Two-dimensional gel electrophoresis (2-DE) coupled with tandem mass spectrometry was employed to reveal the proteins involved in PhA-mediated PDT in LNCaP and PC-3 prostate cancer cells. RESULTS: After PhA-PDT treatment, decreased expression of translationally-controlled tumor protein (TCTP) was found in both PC-3 and LNCaP whole-cell proteomes. In contrast, human rab GDP dissociation inhibitor (GDI) in LNCaP cells and ras-related homologs GDI in PC-3 cells were up-regulated. CONCLUSIONS: GDP-GTP exchange is an underlying target of photodynamic treatment in prostate cancer cells.

Genome-Wide Analyses of the Soybean F-Box Gene Family in Response to Salt Stress.

The F-box family is one of the largest gene families in plants that regulate diverse life processes, including salt responses. However, the knowledge of the soybean F-box genes and their roles in salt tolerance remains limited. Here, we conducted a genome-wide survey of the soybean F-box family, and their expression analysis in response to salinity via in silico analysis of online RNA-sequencing (RNA-seq) data and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) to predict their potential functions. A total of 725 potential F-box proteins encoded by 509 genes were identified and classified into 9 subfamilies. The gene structures, conserved domains and chromosomal distributions were characterized. There are 76 pairs of duplicate genes identified, including genome-wide segmental and tandem duplication events, which lead to the expansion of the number of F-box genes. The in silico expression analysis showed that these genes would be involved in diverse developmental functions and play an important role in salt response. Our qRT-PCR analysis confirmed 12 salt-responding F-box genes. Overall, our results provide useful information on soybean F-box genes, especially their potential roles in salt tolerance.

Comparison of Small RNA Profiles of Glycine max and Glycine soja at Early Developmental Stages.

Small RNAs, including microRNAs (miRNAs) and phased small interfering RNAs (phasiRNAs; from PHAS loci), play key roles in plant development. Cultivated soybean, Glycine max, contributes a great deal to food production, but, compared to its wild kin, Glycine soja, it may lose some genetic information during domestication. In this work, we analyzed the sRNA profiles of different tissues in both cultivated (C08) and wild soybeans (W05) at three stages of development. A total of 443 known miRNAs and 15 novel miRNAs showed varying abundances between different samples, but the miRNA profiles were generally similar in both accessions. Based on a sliding window analysis workflow that we developed, 50 PHAS loci generating 55 21-nucleotide phasiRNAs were identified in C08, and 46 phasiRNAs from 41 PHAS loci were identified in W05. In germinated seedlings, phasiRNAs were more abundant in C08 than in W05. Disease resistant TIR-NB-LRR genes constitute a very large family of PHAS loci. PhasiRNAs were also generated from several loci that encode for NAC transcription factors, Dicer-like 2 (DCL2), Pentatricopeptide Repeat (PPR), and Auxin Signaling F-box 3 (AFB3) proteins. To investigate the possible involvement of miRNAs in initiating the PHAS-phasiRNA pathway, miRNA target predictions were performed and 17 C08 miRNAs and 15 W05 miRNAs were predicted to trigger phasiRNAs biogenesis. In summary, we provide a comprehensive description of the sRNA profiles of wild versus cultivated soybeans, and discuss the possible roles of sRNAs during soybean germination.

QTLs Regulating the Contents of Antioxidants, Phenolics, and Flavonoids in Soybean Seeds Share a Common Genomic Region.

Soybean seeds are a rich source of phenolic compounds, especially isoflavonoids, which are important nutraceuticals. Our study using 14 wild- and 16 cultivated-soybean accessions shows that seeds from cultivated soybeans generally contain lower total antioxidants compared to their wild counterparts, likely an unintended consequence of domestication or human selection. Using a recombinant inbred population resulting from a wild and a cultivated soybean parent and a bin map approach, we have identified an overlapping genomic region containing major quantitative trait loci (QTLs) that regulate the seed contents of total antioxidants, phenolics, and flavonoids. The QTL for seed antioxidant content contains 14 annotated genes based on the Williams 82 reference genome (Gmax1.01). None of these genes encodes functions that are related to the phenylpropanoid pathway of soybean. However, we found three putative Multidrug And Toxic Compound Extrusion (MATE) transporter genes within this QTL and one adjacent to it (GmMATE1-4). Moreover, we have identified non-synonymous changes between GmMATE1 and GmMATE2, and that GmMATE3 encodes an antisense transcript that expresses in pods. Whether the polymorphisms in GmMATE proteins are major determinants of the antioxidant contents, or whether the antisense transcripts of GmMATE3 play important regulatory roles, awaits further functional investigations.

Molecular phylogeny and dynamic evolution of disease resistance genes in the legume family.

BACKGROUND: Legumes are the second-most important crop family in agriculture for its economic and nutritional values. Disease resistance (R-) genes play an important role in responding to pathogen infections in plants. To further increase the yield of legume crops, we need a comprehensive understanding of the evolution of R-genes in the legume family. RESULTS: In this study, we developed a robust pipeline and identified a total of 4,217 R-genes in the genomes of seven sequenced legume species. A dramatic diversity of R-genes with structural variances indicated a rapid birth-and-death rate during the R-gene evolution in legumes. The number of R-genes transiently expanded and then quickly contracted after whole-genome duplications, which meant that R-genes were sensitive to subsequent diploidization. R proteins with the Coiled-coil (CC) domain are more conserved than others in legumes. Meanwhile, other types of legume R proteins with only one or two typical domains were subjected to higher rates of loss during evolution. Although R-genes evolved quickly in legumes, they tended to undergo purifying selection instead of positive selection during evolution. In addition, domestication events in some legume species preferentially selected for the genes directly involved in the plant-pathogen interaction pathway while suppressing those R-genes with low occurrence rates. CONCLUSIONS: Our results provide insights into the dynamic evolution of R-genes in the legume family, which will be valuable for facilitating genetic improvements in the disease resistance of legume cultivars.