水稻Hd1基因节律性分子调控机制及其对抽穗期的影响

水稻抽穗期代表茎顶端分生组织从营养生长到生殖生长转换的早晚，抽穗期决定了品种的地域分布和产量。本课题组前期鉴定了调控水稻抽穗期的C3HC4类RING结构域的E3泛素连接酶HAF1，HAF1通过泛素化降解Hd1和OsELF3，分别调控水稻在短日照和长日照条件下的抽穗期。本研究鉴定了与HAF1互作的bHLH类转录因子HIP4，拟通过突变体表型、基因表达及蛋白互作的研究，系统解析HAF1泛素化降解HIP4及HIP4调控Hd1表达的分子机制，从而回答HAF1在转录水平和蛋白水平是如何调控Hd1昼夜节律性表达影响水稻抽穗期的；利用水稻核心种质资源的基因组测序信息，评估HAF1、HIP4及Hd1不同单倍型组合对水稻抽穗期的贡献。本项目的研究将为水稻抽穗期遗传改良奠定理论基础。

Heading date indicates the time of transition of the shoot apex meristem from vegetative to reproductive phase in rice. Rice heading date determines the variety growth adaptation in various growth seasons and regions. Our previous study has identified a novel C3HC4 RING domain-containing E3 ubqutin ligase HAF1 (Heading date Associated Factor 1). HAF1 mediates ubiquitination and targets degradation of Hd1 and OsELF3, which control the heading date under short and long day conditions, respectively. In this study, we have identified a novel bHLH transcription factor HIP4 (HAF1 Interaction Protein 4), which physically interacts with HAF1. Through analysis of mutants phenotype, gene expression and protein inteactions, we will further examine the molecular mechanisms of ubiquitin-dependent degradation of HIP4 mediated by HAF1 and transcriptional expression of Hd1 regulated by HIP4. Thus, we will address how HAF1 controls the circadian rhythm of Hd1 expression at transcriptional and protein levels to influence heading date in rice. Furthermore, based on the whole genome re-sequencing of the rice core collection, we will evaluate the contribution of the haplotypes combinations of HAF1, HIP4 and Hd1 to control the heading date. This project will preliminarily provide a theoretical fundamental basis for genetic improvement of heading date in rice.