衰老是叶片发育的最终阶段，受植物自身及外界环境等多因素影响，并受多基因调控。功能叶过早衰老直接影响作物产量及品质，因此对其研究具有重要意义。植物类受体激酶（Receptor-like kinases，RLKs）参与多种信号感知及早期传递，但其如何介导叶片衰老信号转导尚不明确。申请人前期工作证明水稻凝集素类受体激酶 Salt Intolerance 1 (SIT1)负调节植物耐盐性。后续研究发现SIT1在叶片衰老时期表达量上升，sit1-1缺失突变体叶片明显晚衰，而SIT1过表达后导致叶片早衰，且脱落酸可能参与该过程。本项目以前期工作为基础，以突变体sit1-1及SIT1过表达等转基因水稻为材料，利用分子生物学、生物化学及遗传学等手段，研究SIT1在叶片衰老过程中的表达模式及激酶活性变化，明确其参与叶片衰老调控的作用机制及信号通路，为寻找水稻叶片衰老信号上游转导组分及分子育种提供线索。

Leaf senescence, the final stage of leaf development, is affected by internal and external factors and is regulated by gene regulatory networks. Precocious senescence of functional leaf directly affects crop yield and quality, making the research of it significant importance. Receptor-like kinases (RLKs) involve in multiple signals perception and early transduction, but function in leaf senescence signaling transduction remain largely unknown. Our previous study proved that SIT1, a lectin RLK, negatively regulates salt tolerance in rice (Oryza sativa). Further study shows that the expression level of SIT1 is upregulated during leaf senescence. A null allele of SIT1, sit1-1, shows delayed leaf senescence, while overexpression of SIT1 causes the opposite phenotype in rice. Abscisic acid (ABA) is found to involve in this process. We will illuminate the temporal and spatial expression profile of SIT1 and the changes in SIT1 kinase activity during leaf senescence. We also attempt to investigate the underlying molecular mechanism and the signaling pathway of SIT1-mediated leaf senescence by using the combined approaches of molecular biology, biochemistry and genetics. We hope our study will uncover the upstream components of leaf senescence signaling pathway and provide valuable clues for molecular breeding.