衰老黄化是导致绿叶蔬菜采后损失和限制其贮运与销售的关键因素。我们前期研究表明，光照处理显著诱导采后生菜可溶性糖累积，抑制叶绿素降解，延缓其衰老黄化，因此推测累积的可溶性糖可能参与调控叶片衰老黄化进程。以往国内外主要从呼吸底物和能量代谢角度研究糖的保鲜作用，近年来研究证实糖也作为一种信号物质参与植物生长和衰老调控。本项目拟以生菜为试材，采用叶圆片培养方法，从信号转导途径探讨糖累积对生菜衰老黄化的调控机制。研究首先揭示光照诱导采后生菜可溶性糖累积规律，阐明糖累积调控叶片衰老黄化进程；在此基础上从依赖和不依赖己糖激酶（HXK）信号转导途径研究糖和糖类似物能否激发糖信号基因、衰老基因、叶绿素酶基因等下游基因表达和衰老黄化参数应答，从而在物质代谢、酶活性和基因水平上解析糖累积对生菜衰老黄化调控的糖信号依赖途径。研究结果为糖对果蔬保鲜信号作用机制增添新内容，也为光照技术在果蔬保鲜中的应用提供科学依据。

Senescence and yellow are key factors that result in postharvest losses and limit the shelf life of leafy vegetables during storage and sale. Our previous researches found that light exposure during storage could significantly induced soluble sugar accumulation and inhibited chlorophyll degradation, and thus delayed postharvest senescence and yellow of lettuce. In the past, most studies demonstrated that soluble sugar played a role of respiratory substrate and energy in preserving fruits and vegetables postharvest quality. However, recent literatures indicate sugar involved in the regulation of plant growth and senescence as a signal substance. The aim of this project will reveal sugar signalling transduction pathway mechanism of soluble sugar affecting postharvest senescence and yellowing of lettuce during storage. The study firstly reveal the regular pattern of soluble sugar accumulation induced by light treatment in lettuce, and then clarify effects of sugar accumulation on postharvest senescence and yellowing of leaves. The main tasks is to focus on dependent and/or independent hexokinase (HXK) sugar signaling transduction pathway by comparing the effect of sugar and sugar analogues on downstream genes such as sugar signaling gene, senescence gene, chlorophyllase genes expression and senescence and yellowing indexes reponses during storage. The results obtained will not only theoretically enrich the sugar signaling mechanism of soluble sugar, but also practically provide scientific data for application of light exposure treatment in preservating of fruits and vegetables.