影响小麦籽粒产量的细胞分裂素平衡关键基因及其有益等位基因的发掘与功能分析

Several recent studies of the molecular basis of grain yield indicate that the cytokinins (CK) are key factors in determining grain yield. It is now clear that the homeostasis of endogenous CKs is coordinately regulated by at least four multi-gene families encoding isopentenyl transferases (IPT), cytokinin oxidases (CKX), zeatin O-glucosyltransferases (ZOG), and β-glucosidases (GLU), and that genetic manipulation of these genes can increase the level of endogenous CKs which may favorite flower and seed development and enhance grain yield. While wheat is a major food crop worldwide, little is known about the CK homeostasis and its role in regulating grain yield in this species. To date, only few CKX genes and one GLU gene have been isolated from wheat. Functional studies of the currently available genes have largely been hampered by the less availability of genetic transformation systems in this species. Previously, we have isolated almost all the family members of IPT, CKX, ZOG and GLU genes and their homoeologs in different sub-genomes of wheat. In planta temporal and spatial expression patterns of these genes and their homoeologs during leaf and reproductive development were elucidated using multiple RNA-seq transcriptome data and RT-qPCR technique. Putative genes/homoeologs playing key roles in enhancing the grain formation and development have be determined. In the present project, we are going to create and identify series of mutants/alleles for each key gene/ by screening TILLING and Eco-TILLING populations in combination with the High Resolution Melt (HRM) analysis. Functional analysis of theses alleles will be carried out through phenotypic investigation, mRNA level and endogenous CK analysis of the mutant carrying M3 plants. These results will provide more information underpining the molecular basis of the CK homeostasis and its role in regulating grain yield in wheat. Mutant alleles beneficial for grain yield improvement will be determined，and functional markers will be developed and introduced into wheat MAS breeding or traditional breeding programs.

细胞分裂素（CK）是调控植物籽粒发育的关键因子之一。植物內源CK的平衡是由编码异戊烯基转移酶（IPT）、细胞分裂素氧化酶（CKX）、玉米素-O-葡糖糖基转移酶（ZOG）和β-葡萄糖苷酶（GLU）等多基因家族协同调控的。对某些基因家族成员的遗传操作可有效改变植物生殖器官的内源CK水平，进而提高籽粒产量。小麦是重要的粮食作物，但国内外对CK平衡基因的研究严重滞后。除本项目申请人外，迄今仅克隆到少数CKX基因和1个GLU基因，转基因技术的限制也制约了基因功能研究。本项目拟在前期对多数IPT、CKX、ZOG和GLU家族成员及其部分同源基因的克隆和大规模定量表达研究的基础上，采用高分辨率熔解曲线PCR扫描小麦TILLING和Eco-TILLING群体，获得各关键基因的系列突变等位基因，并对多个系列等位基因进行功能分析，揭示內源CK平衡及其调控籽粒产量的分子机理，并为小麦高产育种提供有益等位基因，并开发出相应的功能标记，应用于小麦的分子设计育种。

细胞分裂素在植物生长发育过程中扮演了重要的角色，也是调控植物籽粒发育的关键因子之一。对某些基因家族成员的遗传操作可有效改变植物生殖器官的内源CK水平，进而提高籽粒产量。小麦是重要的粮食作物，但国内外对CK平衡基因的研究相对其他作物严重滞后。本项目采用小麦TILLING和Eco-TILLING群体与HRM扫描技术相结合的策略，通过对多个关键基因的系列等位基因的同步分析，建立了一个既能对大量小麦目的基因同步进行基因功能研究，又可以为小麦育种创造有益等位基因的综合研究平台。并较系统揭示了小麦內源细胞分裂素平衡的分子机理及其对调控小麦籽粒产量和其他重要农艺性状的关系。获得了20多个籽粒产量性状有益等位基因，并开发出相应的功能标记。