TaGS3调控小麦籽粒大小的生物学功能研究与功能标记开发

Heterotrimeric G-protein mediates growth and development by perceiving and transmitting signals in multiple organisms. Gγ subunit determines the specificity of the signal transduction pathways. Our previous results revealed that there are five splicing isoforms of TaGS3 (Gγ), which translate five proteins with different domains, whereas alternative splicing has not been reported in Arabidopsis and rice. It is speculated that alternative splicing of TaGS3 may be an important regulation pattern invloved in kernel traits in wheat..Common wheat is an allohexaploid grass species (AABBDD, 2n=6x=42). Our project will focus on: First, ion beam-induced mutant library was used to select three TaGS3 homoeologs single mutants which are crossed each other to obtain the double and triple mutants for analyzing the grain size. The results obtained from these mutants will be helpful to clarify the function diversity of the three TaGS3 homoeologs (TaGS3-A, TaGS3-B and TaGS3-D) and the collaborative relationship between homoeologous genes. Second, transgenic wheat lines harboring different splicing isoforms of TaGS3 will be used to analyze the kernel traits and identify the splicing isoform which positively regulates the grain size. Using yeast-two/three hybrid and BiFC, the combining ability of splicing isoforms of TaGS3 with Gα and Gβ will be investigated. Third, using MCC, KJ-RIL and bred variety population, the haplotypes and allelic variation of TaGS3 will be studied and functional molecular markers of TaGS3 favorable haplotypes will be developed. Eventually, our work will provide gene resources and functional markers in molecular breeding to improve kernel weight in common wheat.

异源三聚体G蛋白通过调控信号传递介导生物体生长发育，Gγ亚基决定了细胞信号转导的特异性。我们的研究表明，不同于拟南芥和水稻，小麦TaGS3 (Gγ) 存在5种RNA剪接形式，产生5种不同的蛋白质。.本课题利用 TaGS3不同染色体组同源基因(TaGS3-A、TaGS3-B和TaGS3-D)的缺失突变体进行籽粒大小的表型分析，明确同源基因生物学功能差异及位点间的协同作用；通过分析TaGS3不同剪接形式的转基因植株籽粒性状，筛选出对小麦籽粒大小起正向调控作用的剪接形式；通过酵母双/三杂交、BiFC等手段检测不同剪接形式与Gα和Gβ的结合能力，阐明TaGS3不同剪接形式参与小麦籽粒大小调控的作用机制；利用微核心种质、KJ-RIL及育成品种群体，发掘TaGS3优异等位变异，开发功能标记用于分子育种。.研究结果将丰富多倍体小麦基因功能分化和调控的理论体系，更为分子育种提供基因资源和功能性分子标记。

异源三聚体G蛋白通过调控信号传递介导生物体生长发育，Gγ亚基决定了细胞信号转导的特异性。小麦是异源六倍体，TaGS3 (Gγ) 有3个染色体组同源基因（TaGS3-7A,TaGS3-4A,TaGS3-7D）。本课题利用小麦微核心种质（MCC）分析TaGS3-4A核酸序列，检测到15个多态位点，通过开发的两个分子标记，将TaGS3-4A区分为5种单倍型。通过关联分析表明，HAP-4A-1和HAP-4A-2为优异单倍型，且在驯化过程中经历了强烈的选择，可以显著增加小麦籽粒的千粒重和粒长。此外，TaGS3-4A和TaGS3-7D同源基因的互作对籽粒性状具有显著的加性效应。Hap-4A-1/ Hap-7D-2单倍型组合是提高小麦产量的最佳单倍型组合。利用343个中国现代栽培品种(MC)，478个北美品种，53个CIMMYT 品种，382个欧洲品种，82个前苏联品种，50个澳大利亚品种，对TaGS3-4A和TaGS3-7D单倍型的全球分布进行了分析。. TaGS3克隆过程中发现其存在5种可变剪接形式。通过分析TaGS3不同剪接形式的转基因植株籽粒性状，筛选出对小麦籽粒大小起正向调控作用的剪接形式TaGS3.5，过表达TaGS3.5显著提高籽粒重5.70%，籽粒长4.30%；通过酵母双/三杂交、BiFC等手段检测不同剪接形式与Gα和Gβ的结合能力，阐明了TaGS3不同剪接形式参与小麦籽粒大小调控的作用机制。. 研究结果将丰富多倍体小麦基因功能分化和调控的理论体系，更为分子育种提供基因资源和功能性分子标记。