Clonal growth characteristics and diversity patterns of different Clintonia udensis (Liliaceae) diploid and tetraploid cytotypes in the Hualongshan Mountains.

Polyploidization plays an important role in plant evolution and biodiversity. However, intraspecific polyploidy compared to interspecific polyploidy received less attention. Clintonia udensis (Liliaceae) possess diploid (2n = 2x = 14) and autotetraploid (2n = 4x = 28) cytotypes. In the Hualongshan Mountains, the autotetraploids grew on the northern slope, while the diploids grew on the southern slopes. The clonal growth characteristics and clonal architecture were measured and analyzed by field observations and morphological methods. The diversity level and differentiation patterns for two different cytotypes were investigated using SSR markers. The results showed that the clonal growth parameters, such as the bud numbers of each rhizome node and the ratio of rhizome branches in the autotetraploids were higher than those in the diploids. Both the diploids and autotetraploids appeared phalanx clonal architectures with short internodes between ramets. However, the ramets or genets of the diploids had a relatively scattered distribution, while those of the autotetraploids were relatively clumping. The diploids and autotetraploids all allocated more biomass to their vegetative growth. The diploids had a higher allocation to reproductive organs than that of autotetraploids, which indicated that the tetraploids invested more resources in clonal reproduction than diploids. The clone diversity and genetic diversity of the autotetraploids were higher than that of the diploids. Significant genetic differentiation between two different cytotypes was observed (P < 0.01). During establishment and evolution, C. udensis autotetraploids employed more clumping phalanx clonal architecture and exhibited more genetic variation than the diploids.

N 6-Methyladenosine and physiological response divergence confer autotetraploid enhanced salt tolerance compared to its diploid Hordeum bulbosum.

Polyploid species have played an essential role in plant evolution, exemplified by adaptive advantages to abiotic stress. N 6-Methyladenosine (m6A) is suggested to play an important role in stress response. However, whether genome doubling affects m6A to increase autopolyploids stress tolerance is still unclear. This study aims to compare physiological (maintaining osmoregulatory homeostasis) and m6A changes between autotetraploid and diploid wild barley (Hordeum bulbosum) in response to salt (NaCl) stress. Results showed that autotetraploids physiologically had enhanced stress tolerance based on the measured parameters of relative water content, water loss, proline, H2O2, and chlorophyll. Diploid H. bulbosum experienced an excessive abundance of proline following salt stress where tetraploids had beneficial proline accumulation and thus enhanced osmoregulation. The significantly higher level of proline and H2O2 in diploid than in autotetraploid implies that diploids suffered higher osmotic stress than autotetraploid. Autotetraploid produced enough proline to protect stress, but not so much to cause toxicity. m6A in total RNA showed no significant difference between ploidies in controls, but was significantly higher in autotetraploids than in diploids during stress and recovery. These results suggest that increased m6A might be one of molecular mechanisms that increases salt tolerance in autotetraploid H. bulbosum compared to diploids, which enhances the adaptation of autopolyploids. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-022-01260-x.

N6-Methyladenosine dynamic changes and differential methylation in wheat grain development.

MAIN CONCLUSION: More methylation changes occur in late interval than in early interval of wheat seed development with protein and the starch synthesis-related pathway enriched in the later stages. Wheat seed development is a critical process to determining wheat yield and quality, which is controlled by genetics, epigenetics and environments. The N6-methyladenosine (m6A) modification is a reversible and dynamic process and plays regulatory role in plant development and stress responses. To better understand the role of m6A in wheat grain development, we characterized the m6A modification at 10 day post-anthesis (DPA), 20 DPA and 30 DPA in wheat grain development. m6A-seq identified 30,615, 30,326, 27,676 high confidence m6A peaks from the 10DPA, 20DPA, and 30DPA, respectively, and enriched at 3'UTR. There were 29,964, 29,542 and 26,834 unique peaks identified in AN0942_10d, AN0942_20d and AN0942_30d. One hundred and forty-two genes were methylated by m6A throughout seed development, 940 genes methylated in early grain development (AN0942_20d vs AN0942_10d), 1542 genes in late grain development (AN0942_30d vs AN0942_20d), and 1190 genes between early and late development stage (AN0942_30d vs AN0942_10d). KEGG enrichment analysis found that protein-related pathways and the starch synthesis-related pathway were significantly enriched in the later stages of seed development. Our results provide novel knowledge on m6A dynamic changes and its roles in wheat grain development.

Origins and chromosome differentiation of Thinopyrum elongatum revealed by PepC and Pgk1 genes and ND-FISH.

Thinopyrum elongatum is an important gene pool for wheat genetic improvement. However, the origins of the Thinopyrum genomes and the nature of the genus' intraspecific relationships are still controversial. In this study, we used single-copy nuclear genes and non-denaturing fluorescence in situ hybridization (ND-FISH) to characterize genome constitution and chromosome differentiation in Th. elongatum. According to phylogenetic analyses based on PepC and Pgk1 genes, there was an E genome with three versions (Ee, Eb, Ex) and St genomes in the polyploid Th. elongatum. The ND-FISH results of pSc119.2 and pAs1 revealed that the karyotypes of diploid Th. elongatum and Th. bessarabicum were different, and the chromosome differentiation occurred among accessions of the diploid Th. elongatum. In addition, the tetraploid Th. elongatum has two groups of ND-FISH karyotype, indicating that the tetraploid Th. elongatum might be a segmental allotetraploid. In summary, our results suggested that the diploid Th. elongatum, Th. Bessarabicum, and Pseudoroegneria were the donors of the Ee, Eb, and St genomes to the polyploid Th. elongatum, respectively.

Molecular regulatory mechanisms underlying the adaptability of polyploid plants.

Polyploidization influences the genetic composition and gene expression of an organism. This multi-level genetic change allows the formation of new regulatory pathways leading to increased adaptability. Although both forms of polyploidization provide advantages, autopolyploids were long thought to have little impact on plant divergence compared to allopolyploids due to their formation through genome duplication only, rather than in combination with hybridization. Recent advances have begun to clarify the molecular regulatory mechanisms such as microRNAs, alternative splicing, RNA-binding proteins, histone modifications, chromatin remodelling, DNA methylation, and N6 -methyladenosine (m6A) RNA methylation underlying the evolutionary success of polyploids. Such research is expanding our understanding of the evolutionary adaptability of polyploids and the regulatory pathways that allow adaptive plasticity in a variety of plant species. Herein we review the roles of individual molecular regulatory mechanisms and their potential synergistic pathways underlying plant evolution and adaptation. Notably, increasing interest in m6A methylation has provided a new component in potential mechanistic coordination that is still predominantly unexplored. Future research should attempt to identify and functionally characterize the evolutionary impact of both individual and synergistic pathways in polyploid plant species.

MiR396 regulatory network and its expression during grain development in wheat.

Wheat contains the largest number of miR396 family with 17 miR396 in Poaceae. MiR396 regulatory network underlying wheat grain development has not comprehensively been explored. Our results showed that precursor miR396 family in Poaceae exhibited not only conservativeness but also diversification especially in wheat. Five haplotypes were detected in Poaceae species, while 4 haplotypes in wheat with Hap-4 (miR396a) and Hap-5 (miR396n) unique to wheat. GO enrichment analysis of target genes showed that the first 20 enrichment functions of miR396a and miR396n are completely different from each other, and also completely different from miR396(b-g), miR396(h-m), and miR396(o-q). Functional annotation on the 18 target genes shared by miR396(b-g), miR396(h-m), and miR396(o-q) found that 11 of the 18 target genes are growth-regulating factor (GRF) genes. Our results indicated that, during the grain filling stage of wheat, miR396 is involved in the development of grains by regulating the expression of GRF genes (GRF1, GRF6, and GRF9). Although the enrichment function of miR396(b-g), miR396(h-m), and miR396(o-q) is the same, the gene functional networks they formed differ greatly. Our results indicated that polyploidization enriches not only the diversity of miR396 family and its target genes but also gene functional networks in wheat. These results laid foundation for further elucidating function of miR396 gene family underlying wheat grain development.

Phylogenetic analysis of two single-copy nuclear genes revealed origin of tetraploid barley Hordeum marinum.

Sea barley Hordeum marinum is an important germplasm resource. However, the origin of this tetraploid H. marinum subsp. gussoneanum is still unclear, which has caused great perplexity to the exploration and utilization of germplasm resources. We used two single-copy nuclear genes, thioredoxin-like gene (TRX) and waxy1 gene encoding granule-bound starch synthase (WAXY1) to analyze 41 accessions of Hordeum marinum. The phylogenies of different genes told different story of evolution of tetraploids of H. marinum subsp. gussoneanum. The phylogenetic trees showed that two distinct copies of sequences from both genes were detected for some accessions of the tetraploids of H. marinum subsp. gussoneanum, and diploid marinum might also contribute to the origin and evolution of the tetraploid gussoneanum. Our findings suggested that tetraploid more likely originated from the diploids of H. marinum subsp. gussoneanum and another ancestor that might be an extinct unknown diploid species. Homogenization of gene in tetraploids also occurred after polyploidization as both TRX and WAXY1 sequences in some accessions of tetraploid H. marinum subsp. gussoneanum cannot be distinguished, indicating the complicated evolution of this tetraploid.

Insights into the N6-methyladenosine mechanism and its functionality: progress and questions.

N6-methyladenosine (m6A) RNA methylation has become a progressively popular area of molecular research since the discovery of its potentially essential regulatory role amongst eukaryotes. m6A marks are observed in the 5'UTR, 3'UTR and coding regions of eukaryotes and its mediation has been associated with various human diseases, RNA stability and translational efficiency. To understand the implications of m6A methylation in molecular governance, its functionality and mechanism must be initially understood. m6A regulation through its readers, writers and erasers as well as an insight into the potential "cross-talk" occurring between m6A and previously well documented regulatory molecular mechanisms have been characterized. The majority of research to date has been limited to few species and has yet to explore the species- and tissue specific nature or mechanistic plasticity of m6A regulation. There is still a tremendous gap in our knowledge surrounding the mechanism and functionality of m6A RNA methylation. Here we review the formation, removal, and decoding of m6A amongst animals, yeast, and plants while noting potential "cross-talk" between various mechanisms and highlighting potential areas of future research.

Evolutionary patterns of plastome uncover diploid-polyploid maternal relationships in Triticeae.

To investigate the diploid-polyploid relationships and the role of maternal progenitors in establishment of polyploid richness in Triticeae, 35 polyploids representing almost all genomic constitutions together with 48 diploid taxa representing 20 basic genomes in the tribe were analyzed. Phylogenomic reconstruction, genetic distance matrix, and nucleotide diversity patterns of plastome sequences indicated that (1) The maternal donor of the annual polyploid species with the U- and D-genome are related to extant Ae. umbellulata and Ae. tauschii, respectively. The maternal donor to the annual polyploid species with the S-, G-, and B-genome originated from the species of Sitopsis section of the genus Aegilops. The annual species with the Xe-containing polyploids were donated by Eremopyrum as the female parent; (2) Pseudoroegneria and Psathyrostachys were the maternal donor of perennial species with the St- and Ns-containing polyploids, respectively; (3) The Lophopyrum, Thinopyrum and Dasypyrum genomes contributed cytoplasm genome to Pseudoroegneria species as a result of incomplete lineage sorting and/or chloroplast captures, and these lineages were genetically transmitted to the St-containing polyploid species via polyploidization; (4) There is a reticulate relationship among the St-containing polyploid species. It can be suggested that genetic heterogeneity might associate with the richness of the polyploids in Triticeae.

Transcriptome and miRNAs analyses enhance our understanding of the evolutionary advantages of polyploidy.

Polyploid organisms have more than two sets of chromosomes, including autopolyploid via intraspecific genome doubling, and allopolyploid via merging genomes of distinct species by hybridization. Polyploid organisms are widespread in plants, indicating that polyploidy has some evolutionary advantages over its diploid ancestor. Actually, polyploidy is always tightly associated with hybrid vigor and adaptation to adverse environmental conditions. However, why polyploidy can develop such advantages is poorly known. MicroRNAs (miRNAs) are endogenous ∼21 nt small RNAs which can play important regulatory roles in animals and plants by targeting mRNAs for cleavage or translational repression. MicroRNAs are essential for cell development, differentiation, signal transduction, and show an adaptive response to biotic and abiotic stresses. Environmental stresses cause plants to over- or under-express certain miRNAs or synthesize new miRNAs to cope with stress. We have here reviewed our current knowledge on the molecular mechanisms, which can account for the evolutionary advantages of polyploidy over its diploid ancestor from genome-wide gene expression and microRNAs expression perspectives.

Phylogenetic analysis of two single-copy nuclear genes revealed origin and complex relationships of polyploid species of Hordeum in Triticeae (Poaceae).

Two single-copy nuclear genes, the second largest subunit of RNA polymerase II (RPB2) and thioredoxin-like gene (HTL), were used to explore the phylogeny and origin of polyploid species in Hordeum. Our results were partly in accord with previous studies, but disclosed additional complexity. Both RPB2 and HTL trees confirmed the presence of Xa genome in H. capense and H. secalinum, and that H. depressum originated from H. californicum together with other American diploids, either H. intercedens or H. pusillum. American diploids solely contributed to the origin of H. depressum. The Asian diploids, either H. bogdanii or H. brevisubulatum, contributed to the formation of American polyploids except H. depressum. RPB2 and HTL sequences showed that H. roshevitzii did not contribute to the origin of American tetraploids. Our data showed a close relationship between the hexaploids H. procerum and H. parodii and the tetraploids H. brachyantherum, H. fuegianum, H. guatemalense, H. jubatum, and H. tetraploidum. The involvement of the diploid H. pusillum and the tetraploid H. jubatum in the formation of H. arizonicum was also indicated in the HTL phylogeny. Our results suggested a possible gene introgression of W- and P-genome species into the tetraploid H. jubatum and the hexaploid H. procerum.

Origin and Evolution of Allopolyploid Wheatgrass Elymus fibrosus (Schrenk) Tzvelev (Poaceae: Triticeae) Reveals the Effect of Its Origination on Genetic Diversity.

Origin and evolution of tetraploid Elymus fibrosus (Schrenk) Tzvelev were characterized using low-copy nuclear gene Rpb2 (the second largest subunit of RNA polymerase II), and chloroplast region trnL-trnF (spacer between the tRNA Leu (UAA) gene and the tRNA-Phe (GAA) gene). Ten accessions of E. fibrosus along with 19 Elymus species with StH genomic constitution and diploid species in the tribe Triticeae were analyzed. Chloroplast trnL-trnF sequence data suggested that Pseudoroegneria (St genome) was the maternal donor of E. fibrosus. Rpb2 data confirmed the presence of StH genomes in E. fibrosus, and suggested that St and H genomes in E. fibrosus each is more likely originated from single gene pool. Single origin of E. fibrosus might be one of the reasons causing genetic diversity in E. fibrosus lower than those in E. caninus and E. trachycaulus, which have similar ecological preferences and breeding systems with E. fibrosus, and each was originated from multiple sources. Convergent evolution of St and H copy Rpb2 sequences in some accessions of E. fibrosus might have occurred during the evolutionary history of this allotetraploid.

Molecular evidence of RNA polymerase II gene reveals the origin of worldwide cultivated barley.

The origin and domestication of cultivated barley have long been under debate. A population-based resequencing and phylogenetic analysis of the single copy of RPB2 gene was used to address barley domestication, to explore genetic differentiation of barley populations on the worldwide scale, and to understand gene-pool exchanges during the spread and subsequent development of barley cultivation. Our results revealed significant genetic differentiation among three geographically distinct wild barley populations. Differences in haplotype composition among populations from different geographical regions revealed that modern cultivated barley originated from two major wild barley populations: one from the Near East Fertile Crescent and the other from the Tibetan Plateau, supporting polyphyletic origin of cultivated barley. The results of haplotype frequencies supported multiple domestications coupled with widespread introgression events that generated genetic admixture between divergent barley gene pools. Our results not only provide important insight into the domestication and evolution of cultivated barley, but also enhance our understanding of introgression and distinct selection pressures in different environments on shaping the genetic diversity of worldwide barley populations, thus further facilitating the effective use of the wild barley germplasm.

Molecular evolution of Wcor15 gene enhanced our understanding of the origin of A, B and D genomes in Triticum aestivum.

The allohexaploid bread wheat originally derived from three closely related species with A, B and D genome. Although numerous studies were performed to elucidate its origin and phylogeny, no consensus conclusion has reached. In this study, we cloned and sequenced the genes Wcor15-2A, Wcor15-2B and Wcor15-2D in 23 diploid, 10 tetraploid and 106 hexaploid wheat varieties and analyzed their molecular evolution to reveal the origin of the A, B and D genome in Triticum aestivum. Comparative analyses of sequences in diploid, tetraploid and hexaploid wheats suggest that T. urartu, Ae. speltoides and Ae. tauschii subsp. strangulata are most likely the donors of the Wcor15-2A, Wcor15-2B and Wcor15-2D locus in common wheat, respectively. The Wcor15 genes from subgenomes A and D were very conservative without insertion and deletion of bases during evolution of diploid, tetraploid and hexaploid. Non-coding region of Wcor15-2B gene from B genome might mutate during the first polyploidization from Ae. speltoides to tetraploid wheat, however, no change has occurred for this gene during the second allopolyploidization from tetraploid to hexaploid. Comparison of the Wcor15 gene shed light on understanding of the origin of the A, B and D genome of common wheat.

Origin of worldwide cultivated barley revealed by NAM-1 gene and grain protein content.

The origin, evolution, and distribution of cultivated barley provides powerful insights into the historic origin and early spread of agrarian culture. Here, population-based genetic diversity and phylogenetic analyses were performed to determine the evolution and origin of barley and how domestication and subsequent introgression have affected the genetic diversity and changes in cultivated barley on a worldwide scale. A set of worldwide cultivated and wild barleys from Asia and Tibet of China were analyzed using the sequences for NAM-1 gene and gene-associated traits-grain protein content (GPC). Our results showed Tibetan wild barley distinctly diverged from Near Eastern barley, and confirmed that Tibet is one of the origin and domestication centers for cultivated barley, and in turn supported a polyphyletic origin of domesticated barley. Comparison of haplotype composition among geographic regions revealed gene flow between Eastern and Western barley populations, suggesting that the Silk Road might have played a crucial role in the spread of genes. The GPC in the 118 cultivated and 93 wild barley accessions ranged from 6.73 to 12.35% with a mean of 9.43%. Overall, wild barley had higher averaged GPC (10.44%) than cultivated barley. Two unique haplotypes (Hap2 and Hap7) caused by a base mutations (at position 544) in the coding region of the NAM-1 gene might have a significant impact on the GPC. Single nucleotide polymorphisms and haplotypes of NAM-1 associated with GPC in barley could provide a useful method for screening GPC in barley germplasm. The Tibetan wild accessions with lower GPC could be useful for malt barley breeding.

Origin and Reticulate Evolutionary Process of Wheatgrass Elymus trachycaulus (Triticeae: Poaceae).

To study origin and evolutionary dynamics of tetraploid Elymus trachycaulus that has been cytologically defined as containing StH genomes, thirteen accessions of E. trachycaulus were analyzed using two low-copy nuclear gene Pepc (phosphoenolpyruvate carboxylase) and Rpb2 (the second largest subunit of RNA polymerase II), and one chloroplast region trnL-trnF (spacer between the tRNA Leu (UAA) gene and the tRNA-Phe (GAA) gene). Our chloroplast data indicated that Pseudoroegneria (St genome) was the maternal donor of E. trachycaulus. Rpb2 data indicated that the St genome in E. trachycaulus was originated from either P. strigosa, P. stipifolia, P. spicata or P. geniculate. The Hordeum (H genome)-like sequences of E. trachycaulus are polyphyletic in the Pepc tree, suggesting that the H genome in E. trachycaulus was contributed by multiple sources, whether due to multiple origins or introgression resulting from subsequent hybridization. Failure to recovering St copy of Pepc sequence in most accessions of E. trachycaulus might be caused by genome convergent evolution in allopolyploids. Multiple copies of H-like Pepc sequence from each accession with relative large deletions and insertions might be caused by either instability of Pepc sequence in H- genome or incomplete concerted evolution. Our results highlighted complex evolutionary history of E. trachycaulus.

Molecular phylogeny revealed distinct origin of the Y and St genome in Elymus longearistatus (Triticeae: Poaceae).

Cytogenetic data has indicated the presence of St and Y genome in Elymus longearistatus (Boiss.) Tzvelev. However, a random amplified polymorphic DNA (RAPD) based sequence tagged site (STS) study suggested one accession of Pseudoroegneria spicata (Pursh) Á Löve (St genome) as a potential Y genome donor candidate in tetraploid E. longearistatus. To examine the origin of Y genome in and the phylogeny of tetraploid E. longearistatus, sequences of cpDNA (RPS16 and TrnD/T intergenic spacer) and single copy nuclear genes (EF-G and HTL) from eight accessions of E. longearistatus, six StY genomic Elymus species and 62 accessions of diploid in Triticeae were analyzed. The cpDNA data suggested that P. stipifolia (St) is the most likely maternal donor of these six Iranian accessions of E. longearistatus, although P. strigosa could not be excluded. Two nuclear gene data convincingly showed that tetraploid E. longearistatus contains two distinct genomes, St and Y genome. The phylogenetic analyses from both the EF-G and HTL rejected the previous suggestion that accession PI232134 of Pseudoroegneria spicata (Pursh) Á Löve (St genome) was potential Y genome donor to E. longearistatus. Phylogenetic analyses revealed a separation of the Y genome sequences in Iranian accessions of E. longearistatus from the sequences in the Pakistan accession, indicating that geographic isolation might influence the evolution of the Y genome in E. longearistatus.

Cloning and characterization of low-molecular-weight glutenin subunit alleles from Chinese wheat landraces (Triticum aestivum L.).

Low-molecular-weight glutenin subunits (LMW-GS) are of great importance in processing quality and participate in the formation of polymers in wheat. In this study, eight new LMW-GS alleles were isolated from Chinese wheat landraces (Triticum aestivum L.) and designated as Glu-A3-1a, Glu-A3-1b, Glu-B3-1a, Glu-B3-1b, Glu-B3-1c, Glu-D3-1a, Glu-D3-1b, and Glu-D3-1c, which were located at the Glu-A3, Glu-B3, and Glu-D3 loci, respectively. Based on the proteins encoded, the number of deduced amino acids of Glu-B3 alleles was approximately 50 more than those of Glu-A3 and Glu-D3 alleles. The first cysteine of Glu-A3 and Glu-D3 alleles was located at the N-terminal domain, while that of Glu-B3 alleles was found in the repetitive domain, which may lead to the different functioning in forming disulfide bonds. All the eight genes were LMW-m types and the new allele of Glu-B3-1a which had nine cysteine residues may be the desirable LMW-GS gene for improving bread-making quality.

Evolutionary pattern of rDNA following polyploidy in Leymus (Triticeae: Poaceae).

Ribosomal ITS polymorphism and its ancestral genome origin of polyploid Leymus were examined to infer the evolutionary outcome of rDNA gene following allopolyploid speciation and to elucidate the geographic pattern of ITS variation. The results demonstrated that different polyploids have experienced varying fates, including maintenance or homogenization of divergent arrays, occurrence of chimeric repeats and potential pseudogenes. Our data suggested that (1) the Ns, P/F, and St genomic types in Leymus were originated from Psathyrostachys, Agropyron/Eremopyrum, and Pseudoroegneria, respectively; (2) the occurrence of a higher proportion of Leymus species with predominant uniparental rDNA type might associate with the segmental allopolyploid origin, nucleolar dominance of alloploids, and rapid radiation of Leymus; (3) maintenance of multiple parental ITS types in allopolyploid might result from long generation times associated to vegetative multiplication, number and chromosomal location of ribosomal loci and/or recurrent hybridization; (4) the rDNA genealogical structure of Leymus species might associate with the geographic origins; and (5) ITS sequence clade shared by Leymus species from Central Asia, North America, and Nordic might be an outcome of ancestral ITS homogenization. Our results shed new light on understanding evolutionary outcomes of rDNA following allopolyploid speciation and geographic isolation.

Comparison of Acetyl-CoA carboxylase 1 (Acc-1) gene diversity among different Triticeae genomes.

It has widely been documented that life form and mating system have significant influences on genetic diversity. In the tribe Triticeae, several genera contain both annual and perennial species, whereas other genera comprise strictly annual or perennial species. It was suggested that Triticeae annuals have originated from Triticeae perennials. The present study aims to analyze nucleotide diversity of Acc-1 gene among different Triticeae genomes, and attempts to link effects of life history (annuals and perennials) and mating systems. The nucleotide diversity of 364 Acc-1 sequences in Triticeae species was characterized. The highest estimates of nucleotide diversity values (π=0.01919, θ=0.03515) were found for the Ns genome among the genomes analyzed. Nucleotide diversities in the D genome and Ns genome of polyploids are higher than those in respective genomes of diploids, while in the St genome of polyploids, it is lower than that in the St genome of diploids. The averaged π value (0.013705) in the genomes of perennials is more than twice of the value (0.00508) in the genomes of annuals. The averaged π value (0.01323) in the genomes of outcrossing species is two-fold of the value (0.005664) in the genomes of selfer. Our results suggested that the evolutionary history and mating system may play an important role in determining nucleotide diversity of Acc-1 gene in each genome.