粒长作为籽粒重要性状之一，是影响作物产量的重要因素。然而，小麦粒长性状相关基因报道却十分有限。前期工作发现一个新合成异源六倍体小麦后代与亲本相比表现出明显的粒长优势，通过表达谱分析获得了9个表达模式可能影响粒长表型的基因，这些基因不仅在雌蕊或未成熟籽粒中特异高表达，且均为生长素路径成员，预示其很有可能与小麦粒长发育相关。本项目拟采用病毒介导的基因沉默方法（VIGS）结合基因时空表达、激素应答以及遗传群体验证等进一步明确其与粒长的关系；对初步明确功能的1个基因，结合BAC文库筛选、in situ、内源启动子驱动GUS表达、基因组特异VIGS以及亚硫酸氢盐测序等方法，深入探讨其三个部分同源基因共同参与粒长性状调控的协同作用模式，揭示其在合成过程中的表达调控机制,并通过转基因小麦最终验证其功能。本研究从新合成异源六倍体出发，以粒长基因为例，以期为挖掘小麦供体种重要农艺性状基因开辟一条新途径。

Grain length, one of the major grain traits, is one of the important factors determining crop yield. In wheat, however, genes involved in grain development, especially grain length development are hardly reported. We previously found significant grain length growth vigor in newly synthesized allohexaploid wheat derived from a combination of tetraploid wheat accession PI94655 (Triticum turgidum, 2n=28) and diploid wheat accession AS2404 (Aegilops tauschii, 2n=14). By comparative analysis of transcriptome profiles between the progeny and the progenitors, we found nine highly expressed genes in pistil and immature seed. Furthermore, these genes exhibited expression patterns potentially correlated with grain length inheritance patterns during the synthesis of allohexaploid wheat. Together with their natures as genes in auxin pathways, these data strongly suggest that these nine genes are candidate genes involved in grain length development. In this proposal we hence plan to conduct the following works: (1) To further confirm their roles in grain length development using virus-induced gene silencing (VIGS) techniques, supported by tissue-specific and spatiotemporal expression patterns and auxin response assays as well as segregation analysis by genetic population; and (2) To study the functions and regulatory modes of one confirmed gene by studying its homoeoallele expression patterns using in situ hybridization, homoeoallele-specific real time PCR, and GUS expression driven by native promoters. Finally, transgenic wheat expressing the chosen candidate gene using tissue-specific promoter will be generated to further study its potential values for wheat yield improvement. This study takes advantage of newly synthesized allohexaploid wheat as bridging materials to screen and identify grain length genes and to characterize their functions, which may provide a new strategy to mine agronomically important genes from wheat donor species.