拟南芥WRKY75基因参与调控GA介导的开花进程的分子机制研究

Correct timing of the floral transition is crucial for successful reproduction. In Arabidopsis, at least five flowering related pathways were genetically identified. Among them, the gibberellin (GA) pathway mainly functions in flowering control under short-day conditions. Our recent results demonstrated that AtWRKY75 may participate in plant flowering control under SD conditions. Down regulation of WRKY75 confers the plant flower later while overexpression of WRKY75 makes the plants flower markedly earlier than the wild type. The contrasting phenotype in flowering was correlated with the opposite experssion levels of AP1. These results implied that AtWRKY75 may function in the regulation of flowering time under SD conditions. Yeast two-hybrid experiment showed that AtWRKY75 can interact with RGA, GAI and RGL proteins, implying that AtWRKY75 may participate in plant flowering control through the GA signaling pathway. Based on these results, we will further explore the molecular function of AtWRKY75 transcription factor in the regulation of plant flowering control, aiming to the identification of AtWRKY75’s direct target genes， illustrating the signaling pathway and molecular mechanism of plant floral transition that controlled by AtWRKY75..

植物开花转换是植物获得生殖成功的关键所在。拟南芥中存在五条控制开花时间的途径,其中赤霉素(GA)途径主要控制植物在短光照生长条件下的开花反应。本项目拟重点研究AtWRKY75基因如何通过GA途径参与调控植物开花进程的分子机制。前期研究表明WRKY75RNAi植株在短日照条件下延迟开花而过表达WRKY75植株则显著提前开花，基因表达分析发现AP1在WRKY75RNAi突变体中的表达明显较在野生型中低，而在WRKY75高表达植株中则明显提高，暗示WRKY75参与调控植物在短日照条件下的开花进程。Y2H证实WRKY75跟RGA、GAI和RGL在蛋白水平上相互作用，建立起WRKY75跟GA信号途径之间的直接联系。在此基础上我们利用基因芯片和ChIP-Seq技术，寻找WRKY75的直接调控靶基因，构建WRKY75跟其靶基因的调控关系，有效阐明WRKY75参与调控GA介导的开花进程的分子机制.

开花时间受内源和外源信号的严格控制。尽管已有证据表明WRKY转录因子参与了开花调控，但所涉及的分子机制和信号转导途径仍有待进一步解析。在本研究中，我们新鉴定了拟南芥WRKY转录调控因子WRKY75作为开花调控的正调控因子。WRKY75突变导致开花延迟，而WRKY75过表达则显著加速了拟南芥的开花进程。基因表达分析表明，WRKY75突变体中开花整合基因FLOWERING LOCUS T (FT)的转录丰度要比WT中低，但在WRKY75过表达植物中则更高。染色质免疫沉淀试验证实WRKY75可以直接调控FT的表达。体内和体外生化分析表明，WRKY75与DELLA蛋白相互作用。我们发现RGL1和GAI都能抑制WRKY75的转录激活功能，从而抑制其对下游基因的调节功能。遗传分析表明，WRKY75以FT依赖的方式正向调节开花，并且RGL1的过表达或GAI的增强功能可部分地延迟WRKY75过表达植物的提前开花表型。我们的结果表明，WRKY75可作为GA介导的信号传导途径的新成分参与调控拟南芥开花进程。