Mutagenic Effects Of Gamma-ray Irradiation On Genome Of Arabidopsis Thaliana

Due to its characteristics of shorter wavelength,higher energy and stronger peretrating power,Gamma-ray,has been the most commonly used physical mutagen in radiation mutation breeding.In this study,dry Arabidopsis thaliana seeds(ecotype: Columbia)that irradiated by gamma-ray were used for mutant screening.The quantitative statistical analysis of mutation rate and mutation spectrum in M2 population were performed to assess the mutagenic effects of gamma-ray at the phenotypic level.Then,based on the whole-genome re-sequencing technology,the types and distribution characteristic of mutations that induced by gamma-ray at DNA level had been analyzed comperhensively.The results,obtained from phenotypical and genomics,will enrich the understanding of the molecular mechanism and biological effectiveness of gamma-ray irradiations on Arabidopsis thaliana,thus may provide the theoretical foundation for gamma-ray radiation mutagenesis on plants.The main conclusion of this research as followed:1.In total,394 plant lines that displayed macroscopic variations were isolated as the putative mutants from 20511 M2 plants,and they were divided into different groups according to their phenotypes: 1)Mutations in the leaf morphology,2)Mutations in the life cycle,3)Mutations in the fertility.The results showed that the total mutation rate of Arabidopsis thaliana irradiated by gamma-ray was 1.92%,the occurrence of leaf mutants and fertility mutants were 1.43% and 0.05%,respectively.In addition,the statistical analysis of pleiotropic phenotypes was performed as well: in the 394 mutant lines,286(72.59%)displayed one conspicuous phenotype,71(18.02%)displayed two conspicuous phenotypes,and 25(6.35%)showed at least three conspicuous phenotypes.Genetic stability investigation showed that there were 79 lines of 394 M2 mutant plants(20.05%)showed stable and heritable phenotypes in the M3.2.Based on the whole-genome resequencing technology,the molecular mutation spectrum of mutations induced by gamma-ray radiation at DNA level analyzed.According to the statistical analysis,a total of 196561469 paired-end reads which covered 22.08 folds were generated,and the average mapped reads account for 90.36%.Detected 432 SNPs and 117 InDels,its ratio was 3.69:1.Among the 432 SNPs,the ratio between the A-G,T-C transition and A-C,A-T,G-C,G-T transversions was 1.27:1.The fragment size of InDels ranged from 1-25 bp,among them,77(65.81%)of the 117 InDels were single base,while 40(34.19%)of the detected InDels were with fragment size ?2bp.3.The distribution of SNPs and InDels is not uniform in the genome.In the whole genome,53.02% of the 549 detected gamma-ray irradiation inducted mutations were occurred in upstream and downstream regions,5.67% occurred in untranslated region,23.03% in the exon,1.28% in the intron and 15.54% in the intergenic region.4.In present study,the GO annotation and classification for the functional genes were also performed.The results showed that the proportion of the mutational genes with related to the biological process were the highest,accounting for 46.24%;the proportion of the mutations in the molecular function and cellular component were 20.05% and 33.71%,respectively.