水稻光敏感卷叶基因PSL1分子调控机制及其抗逆育种利用研究

Rice leaf is the most important organ for photosynthesis, and it's reversible rolling upon dehydration represents an adaptative response to the adverse stresses as such as high light intensity and low humidity, but the molecular regulation mechanisms are still not fully understood. This proposal intends to investigate the function of a candidate gene, PSL1, identified by Map-based cloning on the rice photosensitive leaf mutant, psl1. The differences of the leave shape and nutrient absorption rate between psl1 and its wild-type Nipponbare will be detected with the different light intensity, temperature and relativity thumidity gradient tests in growth chamber; RNA-seq, enzymology, biochemical and cell wall glycomics analyses will be conducted to unravel molecular mechanism by which PSL1 controls the rice leave reversible rolling in response to hydration. By transcription group analysis to find the related genes to PSL1 and identifiing its function, we will explore the regulatory networks between rice leaf-shaped and the ability to resist high light intensity and low humidity adversity stresses. In addition, PSL1 gene pyramiding with other major resistance genes and tissue-specific expression will help with oriented improvement of rice shape to increase light energy utilization efficiency , and carry out the research of rice stress tolerance breeding. This research work will benefit our understanding of the nutrient absorption, transport and metabolism in rice plants, improve the regulatory networks of rice molecules adapting to environmental adversity stresses, and build up a solid theoretical foundation and material basis for super stress tolerance breeding.

水稻叶片是光合作用主要场所，其可回复性失水卷曲是对高光低湿胁迫逆境的一种适应，但分子调控机制仍不清晰。本申请拟在利用水稻光敏感卷叶突变体（photosensitive leaf 1, psl1）进行图位克隆确定候选基因PSL1的基础上，完成PSL1基因功能验证；通过室内不同光、温、湿梯度试验检测psl1及其野生型叶形变化及养分吸收速率差异；同时结合RNA-seq、酶学、生化和细胞壁糖组学分析，解析PSL1调控水稻叶形可回复性卷曲适应强光低湿逆境胁迫的分子机制。通过转录组分析比较筛选与PSL1调节的相关基因并鉴定其功能，探索水稻叶形与耐强光低湿逆境的调控网络。另外，通过PSL1与抗逆基因聚合和组织特异表达，定向改良水稻叶形，增强光能利用率，开展水稻抗逆育种利用研究。本研究有利于了解水稻体内养分吸收及代谢途径，完善水稻适应逆境胁迫的分子调控网络，为超级稻抗逆育种奠定良好的理论基础和材料基础。

叶片是植物光合作用的主要器官，理想的叶片形态有利于提高水稻产量。对叶片极性建立机制进行解析，对探索叶片形态发育的遗传调控网络具有重要意义。近年来，科学家们虽然克隆了多个与叶原基、维管束、厚壁细胞、泡状细胞和表皮细胞发育调控相关的基因，但对细胞壁与叶形发育的关系依旧不够清晰。聚半乳糖醛酸酶是一种果胶降解酶，是细胞壁生物合成的必需酶，其家族成员在植物组织器官中广泛表达，在植物生长发育和病原反应中发挥重要作用。. 本项目利用前期鉴定的“午休”现象明显，但耐旱性显著提高的光敏感的卷叶突变体psl1。表型分析发现，在控制环境光照和湿度的条件下，相对于野生型，突变体psl1在高光或低湿下叶片发生卷曲，水分交换速率和光合效率显著下降。借助图位克隆技术分离了该光敏感卷叶基因PSL1，该基因编码细胞壁中半乳糖醛酸酶，突变体中由于PSL1等位基因发生260bp缺失，导致对高光和低湿的极度敏感。经生化实验表明，PSL1蛋白具有半乳糖醛酸酶活性，突变导致根和叶组织中细胞壁增厚，近轴面泡状细胞覆盖比例增加。另外，细胞壁的改变可以有效的降低体内水分渗透胁迫和干旱条件下的水分损失，耐旱性增强。利用172个细胞壁组分的单克隆抗体对psl1突变体的细胞壁组分进行了分析，发现psl1突变体的细胞壁成分发生显著改变。通过项目实施，初步明确PSL1具有合成半乳糖醛酸酶功能，通过调节水稻细胞壁生物合成来影响植株叶片形态发育。降低PSL1基因在叶片组织中的定向表达，可以有效提高植物对强光和干旱环境的适应性，增强耐旱性。同时，我们也解析了PSL1调节细胞结构和水分代谢方面的作用机制，较好的解释了水稻“午休”现象。研究结果为今后的抗旱分子育种提供了新思路。