自噬信号在褪黑素调控番茄衰老中的作用及机制

Melatonin (melatonin, MT) plays important roles in plant responses to stresses and related signal transduction. Both cell senescence and autophagy are responses of cells to stimuli, however, whether autophagy signal involved in the regulation of melatonin in plant leaf senescence, and whether autophagy signal plays a role in melatonin regulation of tomato senescence are not yet clear. In this project,the main protected cultivation wild type tomato plants, autophagy key gene silencing and overexpressing plants,melatonin synthesis key gene silencing and overexpressing plants will be used as the experimental materials. The response of autophagy signal on plant senescence, regulation of endogenous and exogenous melatonin in leaf senescence, and the effect of melatonin on autophagy mutant plants in the aging process will be analyzed. Gene expression of aging related, metabolic changes of intracellular oxidized proteins and insoluble proteins,as well as other aging markers will be investigated to reveal the relationship between autophagy and melatonin in the process of tomato senescence. The aim of this project is to establish a mechanism model of “melatonin - autophagy - leaf senescence” ,and to provide a theoretical basis for further clarifying the mechanism of melatonin and autophagy involved in plant stress resistance.

褪黑素（melatonin, MT）在植物响应逆境胁迫的信号转导中起重要作用。自噬和细胞衰老都是细胞对刺激的应答方式，然而目前关于褪黑素调控植物叶片衰老是否涉及自噬信号，自噬在褪黑素调控番茄衰老中是否起作用还不清楚。本项目以设施主栽作物番茄、番茄自噬关键基因沉默和超量表达植株、褪黑素合成关键基因沉默和超量表达植株等为试验材料，研究自噬信号对植株衰老的响应、内源和外源褪黑素对叶片衰老的调控，以及褪黑素对自噬基因突变植株衰老的影响，系统分析衰老相关的基因表达、细胞内氧化蛋白和不可溶性蛋白等衰老标志物的代谢变化，揭示自噬和褪黑素在番茄衰老调控过程中的相互关系，建立“褪黑素-自噬-叶片衰老”作用机制模型，为进一步阐明褪黑素和自噬参与植物逆境胁迫抗性机制提供理论依据。

植物衰老涉及遗传、发育、外界环境因子引发等，细胞自噬作用和褪黑素都参与对植物衰老的调控，但在该调控网络中具体的作用机制还不完全清楚。通过项目研究，我们明确了番茄自噬相关蛋白编码基因ATG8f影响褪黑素合成关键基因SlCOMT1的转录，SlCOMT1的缺失也影响到自噬降解途径中的核心蛋白Atg8的积累和光合作用关键基因的表达。在黑暗诱导衰老（DIS）条件下，番茄叶片SlATG8f的转录水平上升和Atg8的表达增加，SlCOMT1的转录水平降低而褪黑素的积累增多；DIS条件下外源褪黑素的补充不能提高衰老植株内源褪黑素含量水平，但是导致Atg8的积累增多，减少MDA、H2O2等伤害物质的积累，提高可溶性蛋白的浓度水平，增强SOD、POD等抗氧化酶的活性。SlCOMT1和SlATG8f缺失导致番茄叶片光系统II（PSII）原初光能转化效率降低，叶片中与蛋白质降解相关的基因被诱导，SlCOMT1和SlATG8f在叶片衰老过程中发挥了促进错误折叠蛋白降解的协同作用，但是SlATG8f的影响作用更大，并且这种作用受内源褪黑素含量水平影响不大，而与自噬标志蛋白的积累相关。