OsMADS27在microRNA444b介导下调控水稻种子萌发的机理探讨

Seed germination is a thread of life of plants that guarantee its survival, thus playing an important role in modern agriculture to increase crop production to feed the growing world population. It is known that seed germination is usually regulated by a series of internal and external factors, especially plant hormones. In the eudicot model plant Arabidopsis, many such seed germination-related factors have been identified, and a relatively clear understanding of germination regulatory networks has been established. However, in monocots such as rice, the function of MADS-box genes involved in the seed germination is still unknown, and the further molecular mechanisms that control germination still need to be elucidated. In this study, we obtained an OsMADS27 loss-of-function mutant of rice and observed delayed germination and increased ABA content phenotypes. This delayed germination could be rescued by expression of OsMADS27, but the precise functional role of this factor remains unknown and requires further investigation. In addition, previous sequence analysis showed that OsMADS27 is one of the target genes of microRNA444b, though there is no direct molecular or functional evidence for this. Therefore, here we also seek to investigate the regulatory roles of miR444b-regulated OsMADS27 inhibiting ABA synthesis in regulating seed germination in rice. This study will help us to better understand the functions of MADS-box genes that are regulated by microRNA, and will supply some direct evidence that demonstrates the integration of multiple regulatory networks of seed germination in rice.

种子萌发作为作物生长并保证产量的关键环节,受众多内外因素（尤其是激素）的复杂调控。双子叶植物拟南芥中已鉴定到一系列参与种子萌发的因子，而且形成了一个主要的调控网络。然而，在作为重要农作物的单子叶植物水稻中，种子萌发的分子机理和调控网络还有待完善。本项目的实验材料是前期工作中得到的一个水稻OsMADS27基因的功能缺失突变体，表现为种子萌发延迟，而且该表型能够很好的被OsMADS27的全长基因组序列所互补。检测发现突变体中ABA含量明显升高。此外，序列分析发现OsMADS27基因是microRNA444b的靶基因之一。本项目的申请旨在探讨OsMADS27基因如何与microRNA444b相互作用通过影响ABA等种子萌发相关激素的含量，进而影响种子萌发的分子机理。本研究的开展将丰富现有受microRNA调控的MADS基因的功能研究，为水稻种子萌发调控网络的整合提供一些科学证据。

1. 研究背景：水稻种子的萌发好坏极大地影响着水稻的产量和品质。我们已经发现OsMADS27基因的突变影响了水稻种子的萌发，但作用机制还不清楚。.2. 研究内容：本研究以水稻种子为研究材料，综合运用发育生物学、细胞生物学、生物化学、分子生物学等原理和方法，着重研究OsMADS27基因对水稻种子萌发的影响及其作用的分子基础。在上述结果基础上，综合分析OsMADS27基因与其上游、下游基因的相互作用，揭示OsMADS27基因的调控网络，从分子水平阐明OsMADS27基因调控水稻种子萌发的生物学机制。.3. 重要结果： OsMADS27基因的突变导致脱落酸ABA含量增加，OsMADS27通过调控ABA合成酶基因OsNCED1和OsNCED5的表达水平来控制ABA的含量，进而影响种子的休眠和萌发；而上游基因miR444b.2对OsMADS27具有负调控作用。.4. 关键数据：osmads27突变体中OsNCEDs基因和miR444b.2小RNA的表达水平数据、EMSA和ChIP实验结果以及稳定遗传的转基因水稻植株。.5. 科学意义：水稻作为重要的粮食作物，其种子萌发及其萌发后的早期生长极大地影响着水稻的产量和品质。本项目的研究结果，将拓宽水稻MADS基因功能的认识，为阐明水稻种子萌发的调控机制提供新的科学依据和理论基础。