砷胁迫下甘蓝型油菜苗期根、下胚轴和鲜重的全基因组关联分析

Genome-wide association of roots,hypocotyls and fresh weight at germination stage under as stress in Brassica napus L.

油菜是修复土壤重金属污染的理想作物,为筛选甘蓝型油菜耐砷性的显著关联单核苷酸多态性位点及相关候选基因,本研究以140份不同来源的甘蓝型油菜自交系为材料,测定和利用油菜60KSNP芯片对正常和砷胁迫条件下的相对根长(RRL)、相对下胚轴长(RHL)和相对鲜重(RFW)进行了全基因组关联分析。结果表明,与RRL、RHL和RFW显著关联的SNP位点分别为15、20和35个,单个SNP位点表型贡献率分别介于13.31%～24.39%、18.04%～33.82%和20.19%～25.06%之间;其中在A02、A07和C02染色体上同时存在与RRL、RHL和RFW显著关联的LD区间。基于油菜基因组信息在LD区间内共筛选到61个可能与砷胁迫相关的候选基因,其中PHT3;3、PHT1;9、GST、OTC5、NRAMP1和ZIP12等与重金属吸收和转运相关。实时荧光定量PCR分析结果表明, PHT3;3和PHT1;9是与甘蓝型油菜砷离子吸收转运相关的重要候选基因。本研究结果对于甘蓝型油菜耐砷胁迫机理的研究、性状的改良具有重要参考价值。

Brassica napus is an optimum crop for repairing the heavy metal pollution of soil. To identify the associated SNP locus and candidate genes with arsenic(As) stress tolerance in B. napus, we measured and performed genome-wide association studies(GWAS) on relative root length(RRL), relative hypocotyl length(RHL), and relative fresh weight(RFW) of 140 rapeseed accessions by the Brassica 60 K Illumina Infinium SNP array. In total, 15 SNPs significantly associated with RRL, 20 loci with RHL, and 35 SNP with RFW were identified, and each of SNP explained 13.31%–24.39%, 18.04%–33.82%, and 20.19%–25.06% of observed phenotypic variation, respectively. The most notable significant SNPs were located on chromosomes A02, A07, and C02, which were repeatedly detected and associated with RRL, RHL, and RFW simultaneously. Based on the rapeseed genome annotation of the linkage disequilibrium(LD) regions, we predicted 61 As resistance of candidate genes, among them, PHT3;3, PHT1;9, GST, OTC5, NRAMP1, and ZIP12, were related to the heavy metal absorbing and transporting. With the results of qRT-PCR, the PHT3;3 and PHT1;9 were obviously induced by As stress treatment in roots, hypocotyls and leaves, indicating that they were the important candidate genes related to As absorption and transport in B. napus. These results provide a reference for elucidating the regulation mechanism of candidate genes and improving agronomic traits in B. napus under As stress.