转录因子OsbZIPC调控水稻粒形的分子机理研究

Grain shape is an important influencing factor in grain yield. The investigation into the grain shape regulation genes may clarify the molecular mechanism of the grain seed development, and can be effectively applied in improving grain yield. We have cloned a bZIP transcription factor named OsbZIPC, which is highly expressed in immature seeds. The preliminary study with the OsbZIPC gene revealed that it is localized in the nucleus, and in the yeast-one-hybrid system, it can bind to the fragments of two starch synthase gene promoters. The OsbZIPC over-expression transgenic plants showed up as higher plant height and larger seeds compared with the wild type. And the RNAi transgenic plants showed up as semi-dwarf and smaller seeds compared with the wild type. Our preliminary study in OsbZIPC revealed that it may be involved in the regulation of starch synthesis to determine grain shape, and also be involved in some other regulation pathway to regulation grain shape. In this study, firstly we plan to apply ChIP-seq technique to disclose the downstream pathways which OsbZIPC gene maybe involved, focus on carbohydrate transport and cell division & differentiation pathways, further investigate into the role of OsbZIPC in the grain shape regulation mechanism, and probe into the possibility of the application of OsbZIPC gene in rice breeding.

水稻籽粒形状是影响稻米产量的重要农艺性状。对调控粒形基因的研究不仅能为阐明水稻种子发育的分子机制奠定基础，而且具有潜在的农业生产价值。我们克隆了一个水稻未成熟种子中高表达的bZIP转录因子，OsbZIPC。过量表达OsbZIPC的转基因植株表现为籽粒变长，株高也略有增加；OsbZIPC的RNAi转基因植株表现为籽粒变短，株高略有减少。研究显示OsbZIPC定位于细胞核中，OsbZIPC蛋白可以结合在两个淀粉合成酶基因的启动子片段上。推测OsbZIPC可能通过调控水稻种子中淀粉合成影响籽粒形状，还可能通过其他途径调控粒形。在本项目中，我们将通过染色质免疫共沉淀和新一代测序技术，重点关注糖类物质转运和细胞分裂与分化途径，从下游基因和遗传调控途径网络的角度，对OsbZIPC基因的调控水稻粒形的分子机理进行探讨，并探索OsbZIPC基因用于水稻育种的可能性。

水稻籽粒形状是影响稻米产量的重要农艺性状。对调控粒形基因的研究不仅能为阐明水稻种子发育的分子机制奠定基础，而且具有潜在的农业生产价值。OsbZIP34是一个水稻未成熟种子中高表达的bZIP转录因子，研究显示OsbZIP34定位于细胞核中，其时空表达模式与糖类在籽粒中时空分布一致。EMSA和ChIP-qPCR实验显示OsbZIP34可以结合淀粉合成途径Wx基因和SBE1基因的启动子片段（含ACGT元件）。进一步利用ChIP-seq技术对OsbZIP34的下游基因进行全基因组扫描，结合酵母单杂实验我们找到了三个下游基因：Os03g0701400（PPR蛋白）、Os08g0109300 (ATP-AMP transphosphorylase )及 Os04g0249500（sucrose synthase7）。过量表达OsbZIP34的转基因植株表现为籽粒变长，株高增加；RNAi转基因植株表现为籽粒变短，株高降低。本研究结果将有助于增加我们对水稻种子发育调控机制的进一步了解，增加水稻育种中可利用的基因资源，具有很好的应用价值。基于本研究结果，已申请中国专利一项。