AtNAP靶基因AtICK5调控拟南芥叶片衰老的分子机制研究

Leaf senescence has a great impact on growth, nutrient accumulation and yield of crop plants. Study on the mechanism of leaf senescence has great theoretical and practical significance in agriculture since yield increase and quality improve can be achieved through controlling or delaying leaf senescence in crops. Recent studies showed that members of ICK gene family are involved in regulating plant cell division, but whether they are involved in the regulation of leaf senescence has not been reported. Our earlier study showed that AtICK5 was likely a direct target gene of AtNAP. The expression of AtICK5 was up-regulated during leaf senescence and the ick5 null mutant displayed a significant delay in leaf senescence. The mutant phenotype can be restored to wild-type by transforming ick5 with the intact AtICK5, suggesting that AtICK5 may be involved in the regulation of leaf senescence. In this study we will further investigate the molecular mechanism of leaf senescence regulation by AtICK5. AtICK5 over-expression lines will be used to confirm the senescence promoting role of AtICK5. Transcriptomic analysis and exogenous plant hormones application on senescence mutants will be conducted to reveal AtICK5 mediated regulatory genes and related signaling pathways. The interaction between AtICK5 and AtNAP will be investigated in vivo and in vitro. Results from this study will for the first time elucidate the role of AtICK5 in regulating leaf senescence and further deepen the understanding of the molecular mechanism of regulating leaf senescence by AtNAP signaling pathway.

叶片衰老影响植物生长、营养积累和产量形成，深入研究叶片衰老调控机制，对控制或延缓植物衰老而提高产量和品质具有重要的理论和实践意义。现有研究表明ICK家族成员广泛参与植物细胞分裂调控，但其是否参与叶片衰老进程尚无报道。前期研究发现AtICK5可能是AtNAP转录因子的下游靶基因，且随叶片衰老表达上调，ick5缺失突变体表现为叶片晚衰，且该表型可被完整AtICK5表达回复到野生型，表明AtICK5可能参与拟南芥叶片衰老调控。本项目将进一步证实AtICK5在叶片衰老过程中的调控作用，通过过表达AtICK5明确其对叶片衰老的促进作用，进一步通过转录组测序和激素处理衰老突变体等方法筛选AtICK5调控的基因及其参与的信号通路。通过AtNAP与AtICK5的体内、外互作实验证实两者的互作关系。本研究将首次明确AtICK5对叶片衰老的促进作用，并进一步加深对AtNAP信号通路调控叶片衰老分子机制的理解。

叶片衰老影响植物生长、营养积累和产量形成，深入研究叶片衰老调控机制，对控制或延缓植物衰老而提高产量和品质具有重要的理论和实践意义。现有研究表明ICK家族成员广泛参与植物细胞分裂调控，但其是否参与叶片衰老进程尚无报道。AtNAP是一个已经报道的具有促进叶片衰老作用的转录因子，其调控叶片衰老的机制有待于进一步发掘。本项目研究发现拟南芥ICK家族成员AtICK5基因随叶片衰老表达上调，atick5缺失突变体表现为叶片晚衰，该表型可被完整的AtICK5表达回复到野生型，过表达AtICK5的拟南芥植株存在叶片早衰的表型，上述结果证实AtICK5参与拟南芥叶片衰老调控，具有促进叶片衰老的功能。杂交获得atnap/AtICK5-OE植株，其仍然存在叶片晚衰表型，但程度弱于atnap突变体，表明AtICK5位于AtNAP下游。酵母单杂交实验、EMSA实验及双荧光素酶报告基因实验，均证实AtICK5是转录因子AtNAP的下游靶基因，且存在多个结合位点。本研究首次明确了AtICK5对叶片衰老的促进作用，并进一步加深了对AtNAP信号通路调控叶片衰老分子机制的理解。