小麦抗穗发芽主基因TaPHS1功能性等位变异发掘及调控网络解析

Pre-harvest sprouting (PHS), happened in all the areas for wheat production worldwide, can cause serious losses in both yield and quality, and thus is one of the major constraints for wheat production. In China, PHS has been happening frequently in middle and lower reaches of the Yangtze River and Southwest Winter Wheat Zones. In recent years, its happening showed an increasing trend in the Huang-Huai Winter Wheat and North China Winter Wheat Zones. To identify and use resistance gene is the most economic way to control PHS. In a former study, we have identified and cloned a major gene for PHS resistance, TaPHS1, identified two causal mutations in this gene that cause the loss of PHS resistance. We also screened the haplotypes of these two mutations in diploid, tetraploid and hexaploid (common) wheat accessions together with PHS resistance, and found some diploid, tetraploid and hexaploid accessions with resistant haplotype but highly susceptible to PHS. In this study, we will continuously clone and sequence TaPHS1 in these accessions to identify the functional allelic variations in diploid, tetraploid and hexaploid wheat; to dissect the gene regulation network of TaPHS1 to better understand the molecular mechanism of TaPHS1 for seed dormancy and PHS resistance; to clarify the distribution of these alleles in wheat germplasm; and to develop diagnostic markers for marker assisted breeding to improve PHS resistance in breeding to safe the wheat production in China.

穗发芽是影响小麦产量和品质的一个重要因素，在全世界各小麦产区均有发生。在我国尤以长江中下游麦区、西南麦区为甚，并在黄淮冬麦区和华北冬麦区呈明显加重趋势。利用抗穗发芽基因选育抗穗发芽品种是防治穗发芽的最经济有效的途径。在已从普通小麦中发掘并图位克隆抗穗发芽主基因TaPHS1，发现基因内两个造成穗发芽抗性丧失的变异，并对部分二倍体、四倍体和普通小麦进行穗发芽抗性鉴定及TaPHS1单体型检测的基础上，本研究拟进一步对发现的呈抗穗发芽单体型但高感穗发芽的二倍体、四倍体、普通小麦中的TaPHS1进行克隆、测序，明确TaPHS1在二倍体、四倍体及普通小麦中的功能性等位变异类型；解析TaPHS1调控的基因网络，进一步阐明TaPHS1控制种子休眠和穗发芽抗性的分子机理；明确各等位变异在小麦品种中的分布；开发可用于高通量标记辅助选择的诊断性标记，应用于小麦育种，提高穗发芽抗性，保证小麦产量和品质的不断提高。

穗发芽严重影响小麦的产量和品质，是包括小麦等主要禾谷类作物生产中的一种世界性灾害,每年都造成严重损失。本研究在前期已图位克隆小麦抗穗发芽基因TaPHS1的基础上，拟对部分普通小麦、硬粒小麦及小麦供体种中发现的易穗发芽、但基因型为已发现TaPHS1内关键变异为抗病单体型的品种进行克隆、测序，鉴定新的功能性等位变异；开发功能性等位变异的KASP标记、并对功能性等位变异在中国小麦品种中的分布及与穗发芽抗性的关系进行检测和分析；解析TaPHS1调控的基因网络并鉴定具有重要调控作用的基因。经过研究，对来自我国黄淮冬麦区、北部冬麦区及长江中下游、西南麦区等小麦主产区的768份小麦品种的穗发芽抗性进行了多点、多年鉴定，发现一批高抗和高感穗发芽的品种；鉴定出63份抗性稳定的高抗种质；通过克隆、测序、关联分析、基因表达分析相结合，在TaPHS1的3’端非翻译区732nt位置鉴定发现了一个新的功能性等位变异，在普通小麦、硬粒小麦中均显著影响穗发芽抗性；发现位于启动子区-222位点的优异变异在我国小麦中分布频率很低，显著影响穗发芽抗性；明确了TaPHS1内-222、+646、+666、732nt四个功能性等位变异在我国小麦种质中的分布情况及其与穗发芽抗性的关系，鉴定出每一位点的优异等位变异及TaPHS1穗发芽抗性最优单体型；构建了TaPHS1的调控网络，发现可能有重要调控作用的基因TaSPT等；鉴定出与TaPHS1互作的蛋白TaVDAC、TaPK等。本研究为利用TaPHS1进行小麦抗穗发芽分子标记辅助育种提供了重要支撑；为进一步深入了解小麦种子休眠与穗发芽抗性的调控机制奠定了重要基础，具有重要重要理论与应用价值。