小麦苗期铅耐受性的全基因组关联分析

Genome-Wide Association Analysis of Lead Tolerance in Wheat at Seedling Stage

【目的】随着工业化的推进,重金属尤其是铅对耕地的污染已成为世界性问题。小麦作为主要粮食作物,其健康生产对保障粮食安全意义重大,筛选铅耐受性强和铅低积累小麦品种、挖掘相关调控基因或 QTL 区间,为耐铅种质创新和揭示小麦铅耐受性遗传机制奠定基础。【方法】采用 140 mg·kg^(-1)的硝酸铅溶液对 102 份小麦品种(系)进行苗期胁迫试验,以 3 个重复下的最大根长、根生物量和生长速率的耐铅系数的加权隶属函数值(D 值)来评价小麦对铅的耐受性。结合小麦 660K SNP芯片的 335 438 个高质量 SNP 标记对小麦铅耐受性进行全基因组关联分析(genome-wide association study,GWAS),挖掘铅耐受性候选基因。【结果】小麦品种(系)之间的铅耐受性表现出丰富的变异,变异系数为 44.8%-46.2%,相关系数介于0.87-0.97(P<0.001);铅耐受性强的品种呈现出铅低积累特性。基因分型结果显示 SNP 多态性信息含量(polymorphic information content,PIC)为 0.28-0.32,群体结构分析将供试材料分为 7 个亚群;2 种 GWAS 分析方法共检测到 20 个与小麦铅耐受性显著关联的 SNP(P≤0.001)和 8 个候选区间,分别分布在 1B、2A、2D、3A、3B、5A 和 7A 染色体上,单个位点可解释 15.33%-19.75%的表型变异,其中 10 个位点和 8 个候选区间在 2 个及以上环境被检测到。分析稳定检测的显著关联位点及区间的候选基因,发现其功能主要与跨膜运输、蛋白修饰以及氧化应激反应有关,包括 7 个与转运蛋白相关基因(TraesCS1B02G433800、TraesCS7A02G118800、TraesCS7A02G117900 等)、2 个与泛素化与去泛素化相关的候选基因(TraesCS2A02G550900 和 TraesCS7A02G477300)、3 个跨膜蛋白基因(TraesCS2D02G570500、TraesCS3B02G039900 和TraesCS3B02G466000)和 1 个过氧化物酶相关的候选基因(TraesCS7A02G474200)。【结论】筛选出铅耐受性强的种质材料 7份,检测到与小麦铅耐受性显著关联的 20 个 SNP 位点及 8 个候选区间,筛选出 13 个与小麦铅耐受性相关的候选基因。

【Objective】With the advancement of industrialization, the pollution of arable land by heavy metals, especially lead, has become a worldwide problem. Wheat is an important food crop, and its safe cultivation is critical to maintaining food security.Screening wheat varieties with strong tolerance to lead, low lead accumulation and mining relevant regulatory genes or QTL regions would lay foundation for further elucidating the genetic mechanism of lead tolerance in wheat. 【Method】The tolerance to lead of102 wheat varieties (advanced lines) were evaluated with a 140 mg·kg;lead nitrate solution at the seedling stage, by the weighted membership function value (D Value) of the lead tolerance coefficients of maximum root length, root biomass and growth rate under three replicates, combining with the 335 438 high-quality SNPs (single nucleotide polymorphism)markers by wheat 660K SNP chip,a genome-wide association study (GWAS) for lead tolerance in wheat was conducted, to mine the candidate genes for lead tolerance in wheat. 【Result】The lead among between wheat varieties (advanced lines) under different replicates showed rich variation, with the coefficient of variation of 44.8%-46.2%, and the correlation coefficient was between 0.87-0.97 (P<0.001). It was found that varieties with strong lead tolerance showed low lead accumulation characteristics. The genotyping results showed that the SNP polymorphic information content (PIC) was 0.28-0.32, the population structure analysis showed that these wheat materials could be divided into 7 subgroups;a total of 20 SNPs and 8 key chromosomal segments that were significantly associated with lead tolerance in wheat (P≤0.001) were detected by two GWAS methods respectively distributed on chromosomes 1B, 2A, 2D, 3A, 3B, 5A, and7A. A single locus explains 15.33%-19.75% of the phenotypic variation, and 10 and 8 key chromosomal segments were detected in two and more environments. Analysis of candidate genes for significant and stable association sites and intervals revealed that the functions of the candidate genes were mainly related to transmembrane transport, protein modification and oxidative stress response,including 7 genes related to transporters, including TraesCS1B02G433800, TraesCS7A02G118800, Traes CS7A02G117900 etc. Two genes involved in ubiquitination and deubiquitination (TraesCS2A02G550900 and TraesCS7A02G477300), three genes encoding transmembrane proteins (Traes CS2D02G570500, TraesCS3B02G039900 and TraesCS3B02G466000), one gene related to peroxidase(TraesCS7A02G474200). 【Conclusion】Seven wheat materials with strong lead tolerance were screened, 20 SNPs in 8 candidate regions significantly related to lead tolerance in wheat were detected, and 13 candidate genes related to lead tolerance in wheat were finally screened.