OsSHI1调控水稻花器官发育的分子机制研究

Floral organ development is fundamental to plant reproduction and the establishment of fruit yield and quality. As one of the most important crops in the world, rice grain yield and quality depends much on the development of floral organ development. We previously identified a novel rice floral organ mutant shi1 with abnormal panicle and floral organ development and significantly reduced seed setting rate, grain weight and quality. Map-based cloning and transgenic complementation demonstrated that the phenotypic variations are controlled by the OsSHI1 gene. Yeast-two hybrid assay revealed that OsSHI1 interacts with MADS transcription factors. However, the coordinated regulation mechanism of floral organ development by OsSHI1 and MADS transcription factors remains unknown. This project mainly addresses three major issues: one is to clarify the expression pattern of OsSHI1 in various floral organs; the other is to validate the effect of OsSHI1 on the function of MADS transcription factors; the third is to elucidate the cooperated regulatory property of downstream target genes. The results of this project can further explain the mechanism of OsSHI1-mediated floral organ development and provide important theoretical guidance for the variety improvement of rice.

花器官的发育是植物繁殖后代和种群扩散的重要手段，同时也是果实产量和品质形成的基础。水稻作为世界上最重要的粮食作物之一，其花器官发育对稻米产量及品质具有显著影响。前期研究中鉴定出了一个新的水稻花器官突变体shi1，其穗型紧凑扭曲，花器官形态异常，籽粒畸形，结实率、千粒重及稻米品质等均显著降低。图位克隆结果表明，该突变性状由转录因子OsSHI1所调控。通过酵母双杂交筛选初步发现，OsSHI1与MADS类转录因子互作。然而，OsSHI1与MADS类转录因子协同调控水稻花器官发育的分子遗传机制尚不明确。因此，本项目主要对以下三方面进行探究：一、鉴定OsSHI1在各轮花器官组织中的表达特性；二、明确OsSHI1对MADS类转录因子蛋白功能的影响；三、阐明OsSHI1与MADS类转录因子对下游基因表达的调控模式。拟通过本项目探究OsSHI1调控水稻花器官发育的分子机制，为水稻品种改良提供理论基础。

花器官的发育是植物繁殖后代和种群扩散的重要手段，同时也是果实产量和品质形成的基础。水稻作为世界上最重要的粮食作物之一，其花器官发育对稻米产量及品质具有显著影响。本项目中鉴定出了一个新的水稻花器官突变体shi1，其穗型紧凑扭曲，花器官形态异常，籽粒畸形，结实率、千粒重及稻米品质等均显著降低。图位克隆结果表明，该突变性状由转录因子OsSHI1所调控。通过荧光定量、免疫印迹、GUS染色及原位杂交等方法验证表明，OsSHI1在各轮花器官组织中均有所表达。对小穗组织地酵母cDNA文库进行双杂交筛选发现，OsSHI1可与E类MADS转录因子互作。进一步蛋白分段验证发现，OsSHI1特异性地与MADS DNA结合结构域互作，该结构域中保守氨基酸地突变显著降低两者地互作强度。OsSHI1与OsMADS1之间的互作并不改变后者地转录及蛋白积累水平，然而，凝胶阻滞及荧光素酶活性分析表明OsSHI1显著抑制OsMADS1的DNA结合及转录活性。染色质免疫沉淀试验证实，在shi1突变体中OsMADS1更加显著富集到下游基因的启动子区中，且OsMADS1下游基因的表达水平显著升高。遗传试验结果表明，E类MADS转录因子过表达转基因植株的产量性状等显著降低，且OsSHI1与OsMADS1协同调控穗部及小花的发育过程。该项目的研究结果不仅解析了OsSHI1介导的水稻花器官发育的分子机制，丰富对植物花器官发育的认知，并为水稻品种改良提供理论基础。