miR1432调节水稻籽粒灌浆充实的作用机制

水稻籽粒灌浆充实的好坏决定了稻米产量的高低及其品质的优劣。项目申请人前期研究已证明，在胚乳中低表达miR1432显著增加转基因株系糙米的千粒重，而高表达miR1432显著降低转基因株系糙米的千粒重。本项目拟在上述研究基础上，采用5’-RACE鉴定预测的miR1432靶基因，并利用转基因技术在胚乳中高表达和低表达miR1432的靶基因，互补miR1432低表达和高表达的表型，结合miR1432的时空表达特性、各转基因株系籽粒灌浆过程中內源激素、蔗糖-淀粉合成代谢相关基因的表达，解析miR1432调节水稻籽粒灌浆充实的调控网络和分子机制；进一步通过测定各转基因株系胚乳细胞的分化和增值过程、籽粒的灌浆速率和大小，籽粒灌浆过程中內源激素含量、蔗糖-淀粉代谢关键酶活性，分析miR1432调节水稻籽粒灌浆充实的生理机制，为利用分子改良育种改善水稻籽粒的灌浆充实，提高水稻的产量和品质提供技术支撑。

Grain weight and quality are always determined by the grain filling. It has been proved that miR1432 have important roles in regulating rice grain filling. Compare with wild-type plant, the brown rice weight of STTM1432 transgenic lines (miR1432 lower expressed) was significantly increased. In contrast, the brown rice weight of MIR1432 transgenic lines (miR1432 higher expressed) was significantly decreased. In this project, 5’-RACE was employed to identify the real target of miR1432.Over-expression and down-expression of miR1432’ target transgenic lines will be generated in rice use endosperm specifically expressed promoter, and the grain filling rate will be investigated in these transgenic lines to detect the downstream target of miR1432 in controlling rice grain filling. Then, endogenous hormone, sucrose and starch metabolism related genes’ expression in endosperm of these transgenic lines will be quantified to study the molecular mechanism of miR1432 in controlling rice grain filling. After that, endosperm cell proliferation, seed size, endogenous hormone content, sucrose and starch metabolism related enzyme activity will be assayed to study the physiological mechanism of miR1432 in controlling rice grain filling. By explaining the mechanism of how miR1432 regulate rice grain filling, it will be helpful to provide theoretical guide for rice yield improvement by means of molecular breeding.