一个新的水稻早衰基因LTS2的克隆与功能分析

水稻是重要的粮食作物，叶片早衰严重制约水稻的正常发育和产量形成，解决水稻叶片衰老问题是育种改良的重要目标。因此，进一步挖掘相关基因阐明早衰调控机制显得尤为重要。本项目前期获得了一个稳定遗传的早衰突变体leaf tip senescence2(lts2)，该突变体呈现植株矮小，分蘖期叶尖开始枯萎，叶绿素含量显著下降，出现明显的早衰现象，产量显著降低。遗传分析表明lts2受单隐性核基因控制,图位克隆将其定位于第10染色体的42kb区间，测序发现突变体中基因A第一个外显子发生单碱基突变，并导致该基因编码提前终止。功能互补确定基因A就是LTS2基因，该基因之前未见报道，被预测编码一个受体激酶，是一个新的调控衰老相关基因。本项目拟通过转基因、表达谱分析、原核表达和胁迫处理等方法对LTS2的功能全面解读，完善调控水稻早衰的遗传机制，丰富水稻育种改良途径。

Rice is the most important crops in the world, leaf premature senescence seriously affects the normal development and yield formation of rice. It is an important goal to solve the leaf senescence problem for breeding improvement. Thus, it is necessary to further explore related genes to elucidate the regulatory mechanism of premature senescence. In this proposal, we have obtained a stable genetic leaf tip senescence mutant, named lts2. This mutant exhibits withered leaf tip at tillering stage, decreased chlorophyll content and significantly reduced yield. This is the obvious phenomenon of premature senescence. Genetic analysis indicates that lts2 is controlled by a single recessive nuclear gene. Via map-based cloning, LTS2 was mapped in a 42 kb region on chromosome 10. Sequencing showed that there is a single base substitution in the first exon of A in this region, which led to the premature termination of the gene coding. The functional complementation analysis verify that A is the LTS2. No papers about this gene were published, so LTS2 is a new gene involved in premature senescence, and is predicted to encode a receptor kinase. Based on these findings, genetical transformations, RNA-seq analysis, prokaryotic expression，enzyme activity assay and stress-tolerance identification will be employed to preliminarily ascertain the biological functions of LTS2. This study will complement the molecular mechanism for regulating premature senescence, enrich the approach for rice breeding improvement.