黄瓜CsSOC1基因参与花打顶形成的分子机制研究

Terminal flower is a major limitation for cucumber greenhouse cultivation in winter-spring season. Our group fine mapping the genetic gene CsTFL1, which is controlling terminal flower by using a mutant, and verified that multiple flower existed in shoot apex in CsTFL1 knockdown lines. In order to clarify the molecular pathways of CsTFL1 in regulation of terminal flower in cucumber, Our group processed transcriptome analysis of CsTFL1 transgenic lines, combining with yeast hybridization system, mined the key regulation gene CsSOC1, which is downstream of CsTFL1 involving terminal flower. The study will conduct CsSOC1 overexpression and knockout transformation to confirm the molecular function in terminal flower; and then mining the close related genes to terminal flower by transcriptome sequencing the CsSOC1 transgenic lines; In addition, yeast one hybrid (Y1H), electrophoretic mobility shift assay (EMSA) and luciferase reporter gene (Luc) technology were used to determine the flowering genes downstream of CsSOC1. This results would be helpful for constructing the molecular regulation network‘CsTFL1-CsSOC1-flowering genes’in terminal flower of cucumber, and also be useful for studying terminal flower in other cucurbit crops.

花打顶是长期困扰我国冬春季设施黄瓜生产的一大难题。本项目组利用花打顶自然突变体图位克隆了花打顶基因CsTFL1，利用转基因技术敲除该基因，导致黄瓜茎尖着生大量花序形成花打顶，通过CsTFL1转基因植株的转录组测序结合酵母杂交研究，发现CsSOC1是位于CsTFL1下游参与花打顶形成的关键基因。本项目将对CsSOC1进行过表达和基因敲除研究，证实其参与花打顶形成的分子功能；对CsSOC1转基因后代及野生型植株进行转录组测序，挖掘其转录调控的开花相关基因；利用酵母单杂交（Y1H）、凝胶迁移（EMSA）和荧光素酶报告基因（Luc）技术，鉴定CsSOC1下游转录调控的关键开花基因，构建“CsTFL1-CsSOC1-开花基因”调控花打顶的分子机制模式，研究结果将为遗传改良手段解决花打顶难题提供科学依据，为其它瓜类作物开展花打顶研究提供理论参考。

本项目通过CsSOC1遗传转化黄瓜获得的过表达株系表现为节间缩短、株高降低以及花芽增多的表型，从而确认CsSOC1基因参与花打顶的形成。对CsSOC1基因的表达分析表明CsSOC1在茎尖生长点和雌花芽中表达较高。利用酵母双杂、BiFC等试验，确认CsTFL1可与CsNOT2a以及开花关键转录因子CsFDP形成复合体，进一步利用酵母单杂、EMSA等分子试验证明CsFDP可与CsSOC1启动子结合。通过分析CsSOC1过表达株系开花相关基因的表达情况，找了到CsSOC1下游开花基因CsLFY，从而提出CsTFL1/CsNOT2a/CsFDP和CsFT/CsNOT2a/CsFDP复合体可能在茎尖分生组织通过竞争性结合CsSOC1启动子从而影响CsSOC1以及下游CsLFY基因的表达最终影响开花的分子模型。该机制的解析可为后续黄瓜花打顶科研和育种工作提供帮助，同时为其他瓜类蔬菜，以及番茄、辣椒等蔬菜开展抗花打顶研究以及培育都市蔬菜品种提供技术职支撑。