| Corn(Zea mays L.)is one of the crops widely planted in the world today.It is also an important crop of food,feed,industrial raw material and energy in China.It plays a great role in promoting the development of national economy,ensuring food security and alleviating energy crisis.The SBP gene family is a type of transcription factors unique to plants.This gene family encodes a kind of multifunctional zinc finger structure,and its transcription level can promote the target gene to activate or inhibit the DNA-binding protein at a specific time and space.Most of the SBP genes were found to be related to the development and ripening of fruit,which is the source of human survival and development.Therefore,SBP gene is of great significance in the study of plant high yield.In this study SBP genes were sequenced using targeted sequence capture technology in 32 teosinte,68 Landraces and 348 maize inbred lines to analyze the sequence polymorphism of SBP genes in three populations and the patterns of evolution during the domestication process.In addition,a total of 15 maize yields related traits were measured.The candidate gene association analysis method was used to mine the favorable alleles significantly associated with agronomic traits.The main research results are as follows:1.Totally,17 members of the SBP gene family were successfully captured in 448 maize lines and analyzed their sequence variation.Sequence polymorphism analysis showed that among 448 maize inbred lines,the 17 SBP genes had the largest number of sbp3 mutation sites(1819)(1504 SNPs and 315 Indel),while the 17 sbp19 gene had the least number of sbp19 mutation sites(343)(218 SNPs and 125 Indel).tsh4 had the highest frequency of mutation loci,with an average of one mutation loci every 5.06 bp.sbp19 had the lowest mutation frequency,with an average of one mutation site per 20.06 bp.It was found that the nucleotide polymorphism of SBP gene was high in the upstream of the start codon,intron and downstream of the stop codon,but was relatively low in the coding region(CDS).From the point of view of domestication,the nucleotide polymorphism of each segment of SBP gene increased in order from maize inbred line,local breed and teosinte.The LD model analysis showed that tsh4,sbp1,sbp27,sbp25 and sbp29 had obvious selection trace.2.In order to further clarify the sequence variation of 17 SBP genes in 348 maize inbred lines,the analysis showed that:Among the 348 maize inbred lines,the 17 SBP genes had the highest number of sbp3 mutation sites(970(786 SNP and 184 Indel)),and the sbp19 gene had the lowest number of sbp19 mutation sites(343(218 SNP and 125 Indel)).Correlation analysis of candidate genes showed that a total of 9 SBP genes were significantly associated with 12 traits.The genetic variation of lgl gene was significantly correlated with spike grain weight(EGW),grain length(KL),grain number in row(KNR)and grain width(KW)traits.The genetic variation of sbp3 gene was significantly associated with panicle diameter,axial diameter and grain weight.The genetic variation of sbp20 gene had significant influence on row number,grain thickness,ear diameter and ear length.Among them,a total of 5 variation loci in sbp3 were associated with ear diameter(ED),and their contribution rates ranged from 6.97%to 8.14%.The sbp20 gene was mapped to 26 loci related to keratin number(KNR),and the contribution rate was 3.41%-5.48%.sbp3 and sbp20 were selected for further study.3.Haplotype analysis of significant variation sites on sbp3 showed that inbred lines could be divided into two haplotypes,in which ear diameter of hap1 was significantly larger than that of hap2.Expression analysis showed that haplotype hap1 of sbp3 was significantly higher than that of hap2.A total of 26 variation loci were found to be significantly associated with row number traits in sbp20,and these variation loci could be divided into four haplotypes.The row number of hap1 and 2 was significantly higher than that of hap3 and Expression analysis showed that the expression levels of hap3 and 4 genes were significantly higher than those of hap1 and 2.4.In order to study the function of sbp3 and sbp20 genes,an EMS mutant of sbp3 was screened from the mutant library,and a homozygous termination mutation was identified.At the same time,three independent homozygous mutation events were obtained by gene knockout of sbp3 using CRISPR/Cas9 gene editing technology.Five homozygous mutants of sbp20 gene were obtained by screening the Mu mutants from the Mu library.Seven independent heterozygous mutations were obtained in sbp20 gene knockout using CRISPR/Cas9 gene editing.This study will provide a better understanding about sequence variation and genetic evolution of the SBP genes during maize domestication.The identified favorable alleles can be used through molecular marker-assisted selection of germplasm improvement. |
PDF Full Text Request