水稻主效基因OsPsbS1调控非光化淬灭自然变异的分子机制研究

Rice is generally cultivated under high natural illumination, and nonphotochemical quenching (NPQ) is a major photoprotective mechanism that always regulates energy conversion in photosystem II and protects plants from photoinhibition. NPQ capacity affects rice sustainable growth and grain yield significantly. OsPsbS1 was found to be a major determinant for natural variation of NPQ capacity. Haplotypes with the 2674-bp insertion in the promoter region exhibited significantly higher NPQ values and higher expression levels of OsPsbS1. Recently, by rapid amplification of the cDNA ends (RACE), we have determined the transcript of FP1, an Open Reading Frame located in the insertion fragment. FP1 can directly bind to the cis-element near the transcription start site of OsPsbS1. The FP1 mutants by T-DNA insertion exhibit significantly decreased NPQ values and lower expression levels of OsPsbS1. sRNA and high levels of DNA methylation are observed in the FP1 genomic region. In addition, one MYB and four bZIP transcription factors have been identified to be able to bind to a promoter region with the highest relative promoter activities. In this research proposal, the regulatory effects of the above-mentioned factors will be further characterized through various approaches. The core cis-elements will be defined, and the DNA binding and transcriptional activation domains of the transcription factors will be revealed. The genetic interaction mode among these factors will be elucidated. The research results will help understand in depth how OsPsbS1 functions for NPQ variation and provide guidance in enhancing photoprotection and photosynthetic efficiency for rice breeding.

水稻生长季节经历典型自然强光辐射，非光化淬灭(NPQ)是其主要的光保护机制。OsPsbS1是控制NPQ值的主效位点，高NPQ值材料在启动子区含有2674-bp的插入序列且OsPsbS1表达水平较高。本研究小组在该插入片段中检测到转录基因FP1，FP1蛋白可以结合到OsPsbS1转录起始位点区域，在FP1的T-DNA插入突变体中OsPsbS1表达量及NPQ值均出现极显著下降，FP1存在小分子RNA及甲基化修饰。还发现启动子一区段内存在增强转录的顺式作用元件，并鉴定出5个能与该区段互作的OsbZIP及OsMYB转录因子。本项目拟进一步通过各种方法阐明以上各因子对OsPsbS1表达量的调控效应，确定关键顺式作用元件核心序列，鉴定各转录因子DNA结合结构域及转录激活结构域，并研究各调控因子间的互作。本研究对于深入理解OsPsbS1调控水稻NPQ值自然变异的机制及指导高光效育种实践具有重要意义。

水稻通常在高自然光强条件下生长，非光化淬灭（NPQ）是其主要的光保护机制。一般典型粳稻NPQ值极显著高于籼稻，连锁与关联分析表明OsPsbS1是控制水稻NPQ值自然变异的主效位点。高NPQ值材料在OsPsbS1启动子区含有2674-bp的插入序列。本项目研究了高NPQ值水稻种质材料在OsPsbS1启动子区的2674-bp插入序列内部存在的关键调控元件，以及这些元件导致典型粳稻比籼稻NPQ值高的分子机制。.本研究发现OsbZIP72直接正向调控OsPsbS1的表达，并极显著影响水稻NPQ值；在典型粳稻OsPsbS1启动子中含有能与其强烈结合的额外顺式元件GACAGGTG，这导致了典型粳稻中OsPsbS1的表达量及NPQ值极显著高于籼稻。OsbZIP72受SAPK1激活，依赖于ABA信号路径。SAPK1通过磷酸化OsbZIP72增强其对OsPsbS1的转录激活活性。本研究还发现OsMYBS2直接下调OsPsbS1的表达，并极显著影响水稻NPQ值。在典型粳稻OsPsbS1启动子中鉴定了其新的核心结合元件序列CTAATC。水稻14-3-3蛋白GF14A通过调控OsMYBS2的质核穿梭影响OsPsbS1基因的表达，且OsMYBS2的Ser53磷酸化对与GF14A蛋白的互作十分关键。OsPsbS1基因表达受高光强显著诱导。与野生型相比，OsbZIP72基因敲除突变体在强光下OsPsbS1基因表达极显著下降；而OsMYBS2基因敲除突变体OsPsbS1基因在弱光下表达显著高于野生型。.本研究首次发现14-3-3蛋白参与调控NPQ过程，且NPQ、ABA信号及逆境信号路径存在交叉。项目研究结果对于深入理解水稻NPQ自然变异主效基因OsPsbS1参与的光保护机制具有重要科学意义，对于水稻高光效育种实践具有重要指导意义。