水稻M2群体中OsNramp5基因同一等位突变后代基因组变异特征OA

During the creation of low-cadmium rice germplasm resources using exon-targeted sequencing technology,two lines,H7-25(H7)and K8-24(K8)carrying the same heterozygous allelic mutation of the OsNramp5 gene were identified in the M2 population derived from rice cultivar Fuxiang 116(FX116)irradiated by 12C6+ion beam.The allelic variation is characterized by a single base deletion at position 8835306(RAP_Locus)in the 13th exon of the OsNramp5 gene.Homozygous mutant lines were subsequently obtained from their progeny through self-pollination,segregation,and identification.In the M7 generation,the novel low-cadmium rice mutant lines both exhibited low-cadmium accumulation in brown rice but showed significant differences in plant height and thousand-grain weight.To explore the effects of radiation mutagenesis on genomic variation in rice,whole-genome resequencing was employed to characterize the genomic variation profiles of the mutant lines.Compared with the wild type,a total of 2 506 and 1 080 single nucleotide polymorphisms(SNPs)were identified in H7 and K8,respectively.Transition was the predominant type of SNP variation,accounting for 74.06％and 74.91％of the total SNPs in two mutants.There were 61 common SNP variants shared by H7 and K8,accounting for only 2.44％and 5.65％of their respective total SNPs.These SNPs were mainly distributed in intergenic regions(59.02％)and concentrated on Chromosome 1(42.63％).The line-specific SNPs unique to H7 and K8 were 2,445 and 1,019,of which 59.96％and 82.73％were located in intergenic regions,respectively.Chromosomal distribution analysis showed that the specific SNPs of both mutant lines were predominantly enriched on Chromosome 1,with proportions of 98.08％and 96.44％,respectively.Additionally,785 and 569 insertions/deletions(InDels)variants were identified in H7 and K8,small fragment deletions(≤2 bp)constituted the major InDel type,represnting 75.28％and 81.72％of the total InDels.There were 182 common InDel variants shared by H7 and K8,accounting for 23.19％and 31.99％of their respective InDels variations.These common InDels were primarily enriched in intergenic regions(60.44％)and concentrated on Chromosome 1 and 6(34.62％and 42.86％,respectively).The mutant line-specific InDels of H7 and K8 were 603 and 387,among which 54.56％and 69.25％were distributed in intergenic regions.These specific InDels were mainly clustered on Chromosome 1,with proportions of 84.74％and 72.35％,respectively.The overall mutation frequency were 7.9×10-6 for H7 and 3.9×10-6 for K8.Validation of selected exonic variants via Sanger sequencing achieved a detection rate exceeding 95％.This study analyzed the genomic divergence between H7 and K8,evaluated the genomic mutation frequency,and systematically characterized the genomic variation patterns of the mutants.The results provide molecular theoretical support for population management,generation advancement,and mutant selection in mutation breeding programs.