拟南芥种子休眠萌发相关因子ESD的功能和分子调控网络研究

Seed dormancy and germination is a very important transition stage from reproductive growth to vegetative growth, which are the pivotal ecological and agricultural traits which directly determine the timing of seed germination and affect crop yield and food quality in agriculture. Transition stages are characterised by specific transcriptomes and require silencing and activation of diverse sets of genes. However, little is known about the molecular mechnisms of seed dormancy and germination. Recently we found that ESD is involved in the regulation of seed dormancy and germination, but nothing is reported about ESD function and roles in plant development in Arabidopsis. Therefore, we make this proposal to further investigate the function of ESD in combining several approaches such as molecular genetics, transcriptomics, physiology and biochemistry to uncover gene regulatory network or genetic regulatory network in regulating seed germination. We will focus on: (1) molecular mechanisms of ESD in seed dormancy and germination; (2) the crosslink between or among the genes related to seed dormancy and germination. The work will be very helpful for improving the crops in the future.

种子休眠与萌发是植物由生殖生长进入营养生长转变的关键时期，是决定植物生存发展的重要生态性状，也是制约作物高产优质的关键农艺性状。由于种子是低含水量高储藏物质低代谢活性的特殊器官，目前对种子休眠和萌发的分子调控机制了解较少。我们通过突变体筛选发现ESD缺失可以导致种子休眠加深，生物信息分析显示ESD为未知功能蛋白，目前还没有关于ESD功能与植物发育相关的报道。因此，项目拟从ESD的分子功能入手，利用生理生化、分子遗传、组学、植物激素生理以及细胞生物学技术等方法，研究ESD调控种子休眠萌发的分子机制，阐述ESD参与调控种子休眠萌发的分子网络，为遗传育种改良作物提高产量和品质提供理论基础。

研究种子休眠和萌发的调控机理对于植物生存和农业生产具有重要的理论意义。拟南芥DOG1（DELAY OF GERMINATION 1）基因是控制种子休眠数量性状位点（QTL）的主效基因，DOG1是促进植物种子休眠的特异性关键因子。鉴定与DOG1功能相关的新成员并解析其作用机理将会进一步完善种子休眠萌发的分子调控网络。通过STRING网站（https://string-db.org/）预测，发现一个未知功能的蛋白与DOG1具有较高的相关性，该蛋白的编码基因初步命名为ESD，后应出版社要求改为AtSdr4L（Arabidopsis thaliana Seed dormancy 4-Like）。研究发现，AtSdr4L基因在拟南芥种子中特异表达，编码蛋白定位于细胞核，功能缺失突变体atsdr4l种子休眠明显加深，AtSdr4L是种子休眠的特异性负调控因子。进一步研究发现，休眠的atsdr4l种子对赤霉素（GA）处理不敏感，后熟的atsdr4l种子萌发对GA合成抑制剂多效唑（PAC）超敏感，并且遗传研究表明AtSdr4L位于GA途径负调控因子RGL2（RGA-LIKE 2）的上游，这些结果暗示AtSdr4L通过介导GA途径调控种子的休眠与萌发。遗传研究同时也发现，atsdr4l能够完全抑制dog1的休眠缺失表型，AtSdr4L是DOG1的遗传上位基因。因此推测AtSdr4L是GA途径和DOG1途径调控种子休眠萌发的重要结点。关于AtSdr4L的生化功能及其调控种子休眠和萌发的分子机理还在进一步研究中。