小麦粒重基因TaGW2三个位点的遗传效应与互作研究

Common wheat is one of important food crops, and its production directly affects standard of living and food security. Grain weight, representing in plant breeding practice by thousand grain weight (TGW), is one of three yield components in common wheat. Cloning yield-related genes, developing functional markers and investigating theirs mechanism of action are greatly important for high-yield breeding in wheat. In the previous project, the homologous gene of OsGW2 was cloned from common wheat based on comparative genomics, and named with TaGW2. Gene diversity of TaGW2 indicated that the sequences were highly conserved in the coding region among cultivars with various grain weights, and diversity of TaGW2-6B was higher than that of TaGW2-6A, but no sequence difference was found on TaGW2-6D. In addition, molecular markers, such as TaGW2-6A-CAPS, TaGW2-6B-ACAS-PCR, TaGW2-6B-CAPS, TaGW2-6B-dCAPS were developed according to several SNP loci, and some of them have been applied to wheat genetic study. Based on building of genotyping system of TaGW2, the objectives of the present project were to analyze the interplay action between three genes of GW2 in wheat, investigate the relatedness between the expression level of genes and grain weight and, detect the evolution pattern of these genes in the polyploidization history of wheat. After dissecting yield-related gene TaGW2 systematically, this project will provide some probable theoretical basis on high-yield molecular breeding programs, and explore a dissection approach of important agronomic traits in wheat.

粒重是小麦产量的三要素之一。克隆小麦粒重基因、开发功能标记并研究其作用机理对小麦高产分子育种具有重要意义。上期项目从小麦中克隆了水稻粒重GW2的同源基因，命名为TaGW2。通过TaGW2基因多样性及分子标记研究发现，不同粒重小麦品种编码区序列高度保守，启动子区域TaGW2-6B多样性高于TaGW2-6A，TaGW2-6D启动子区序列无差异；开发了简易分子标记TaGW2-6A-CAPS和TaGW2-6B-ACAS-PCR、TaGW2-6B-CAPS、TaGW2-6B-dCAPS，部分标记已被国内外同行利用。本项目拟在此基础上，重点从小麦三个GW2基因互作分析、基因表达差异与粒重关系研究、基因在多倍体化过程中的进化规律探讨三个方面进一步解析小麦粒重基因TaGW2。本项目从当前的小麦生产需求出发，系统剖析产量相关基因，将为小麦高产分子育种提供一些理论基础，为复杂的小麦农艺性状研究开辟思路。

TaGW2是一个粒重相关基因，主要影响小麦粒宽和千粒重。本项目是国家青年科学基金项目“小麦粒重相关基因TaGW2多样性及其分子标记研究（30900898）”的延续，前期研究完成了TaGW2基因克隆、核苷酸多态性检测、有效分子标记开发、验证及不同单元型全球小麦地理分布特征等方面的分析。在此基础上，该项目系统、深入地解析了TaGW2同源基因单元型间互作、表达模式差异及多倍体进化规律。研究发现，TaGW2s基因在全球小麦育种过程中经历了强烈的选择，且优异单元型组合（Hap-6A-A/Hap-6B-1）存在一定的加性效应；无论粒宽或粒重，TaGW2-6B表型解释率均高于TaGW2-6A，TaGW2-6A/TaGW2-6B组合的表型解释率高于单个基因。TaGW2s基因在小麦籽粒发育过程中对粒宽及粒重呈负调控作用。大粒型单元型Hap-6A-A和Hap-6B-1平均相对表达量均低于同一位点上的小粒型单元型；伴随着多倍化及驯化过程中粒宽和千粒重的提高，TaGW2s基因相对表达水平降低，进一步证实TaGW2s负调控小麦粒宽和粒重。在小麦进化和改良过程中，TaGW2s基因受到了强烈的选择作用，在启动子区的选择强度要高于编码区。TaGW2三个同源基因从二倍体到四倍体，再到六倍体核苷酸多态性及单元型数目显著降低；在整个启动子区和编码区，TaGW2-6B多样性最高，TaGW2-6A次之，TaGW2-6D多样性最低。TaGW2s在不同倍性材料间和不同区域间伴随多倍化过程均存在一定程度的分化，二倍体到四倍体间的遗传分化显著高于四倍体与六倍体间的遗传分化，启动子区的遗传分化程度高于编码区。研究结果将为小麦高产分子设计育种提供重要基因或有效标记，为复杂的小麦农艺性状和小麦多倍化过程中重要农艺性状基因的进化研究提供思路。围绕TaGW2基因互作与进化规律研究，本项目在国际刊物发表相关研究论文3篇，授权国家发明专利1项，培养博士研究生1名。