拟南芥NF-YCs基因参与GA介导种子萌发的调控机制

Seed germination is an indispensable process in plant development and reproduction, and gibberellin (GA) is a crucial hormone which mediates the key process in seed germination and development. However, the underlying molecularmechanism how GA accurately regulates seed germination still remains largely elusive. Our previous work found that: Arabidopsis NF-YCs gene triple mutant (nf-yc3 nf-yc4 nf-yc9) seeds were more resistant to paclobutrazol (PAC, a GA biosynthesis inhibitor) than wild type, while overexpression of NF-YC9 or NF-YC3 transgenic seeds were hypersensitive to PAC; the NF-YC9 could interact with RGL2, the key GA repressor of seed germination, in vivo and in vitro,; NF-YC9 directly binds promoter of DELLA downstream gene XTH5. Hence, we hypothesise that NF-YCs might be involved in seed germination regulation by GA. Here, we mainly focuse on the functional analysis of Arabidopsis NF-YC9 and its homologous genes in seed germination, further understanding the molecular mechanism of NF-YCs and DELLA proteins interaction involved in downstream transcriptional regulation during seed germination process. These results will shed lights on GA signal transduction and regulation in seed germination.

种子萌发是植物发育和繁殖的必需过程，赤霉素（GA）作为主要内源植物激素，介导种子萌发的关键分子信号，然而关于GA如何精确调控种子萌发的具体分子机制仍不十分清楚。我们前期发现：在GA合成抑制剂（PAC）处理下，拟南芥NF-YCs基因同源多突变体（nf-yc3 nf-yc4 nf-yc9）的种子萌发率相比野生型显著提高，表现为PAC不敏感，而过表达NF-YC9或NF-YC3种子对PAC超敏感；NF-YC9与GA介导种子萌发关键抑制因子DELLA蛋白成员RGL2在体内和体外发生蛋白互作；植物体内NF-YC9能直接结合GA下游萌发相关基因XTH5启动子。据此我们推测NF-YCs可能参与GA信号对种子萌发的调控。在此基础上，本项目拟通过对拟南芥NF-YCs基因功能的研究，阐明种子萌发过程中NF-YCs与DELLA蛋白互作机制及对下游基因的转录调控模式，以深入解析GA信号介导种子萌发的调控机理。

种子萌发是植物发育的一个重要阶段，决定着植物何时何地开启生长发育，是自然界物种繁衍与传播的基础，也是保障农业生产的关键性状之一。众多研究表明，种子萌发主要通过植物内源激素GA和ABA相互制衡的方式来调节，然而这两种激素之间发生拮抗的具体分子机制迄今尚未完全明晰。本研究发现Nuclear Factor Y-C（NF-YC）家族基因在调控植物种子萌发中发挥重要作用。拟南芥NF-YC同源基因负调控GA介导种子萌发过程；利用分子生物学手段我们找到了NF-YC的互作因子，即GA介导种子萌发关键抑制子DELLA蛋白RGL2；经高通量测序、遗传及生化分析，结果证实NF-YC和RGL2在转录调控上具有相互依赖关系，二者通过形成复合体共同结合到ABA信号关键调控基因ABI5启动子的CCAAT元件上促进其转录，以此来整合GA和ABA信号，调节种子萌发。该发现阐明了NF-YC-RGL2-ABI5分子模块在种子萌发中的关键作用，促进了对GA和ABA激素互作如何调控植物发育的理论认知。. 项目取得的主要成果为：在国际重要学术期刊发表论文共4篇，皆为第一标注，总影响因子约34。培养博士2名，硕士2名。