糖信号转导途径调节芥子油苷代谢的机理研究

Glucosinolates are a group of secondary metabolites mainly exist in cruciferae plants. Glucosinolates and their degradation products are known to play important roles in plant interaction with herbivores and micro-organisms. In addition, they are also important for human life because of the remarkable anti-carcinogenic activity of their hydrolysis products, isothiocyanates. The biosynthesis and metabolism of glucosinolates are a complex process, which is delicately modulated by multiple signaling molecules. Sugar signaling is one of the best elucidated plant signalling pathways,and its role in plant adaptation to environmental stresses and as source preferred by most organisms was well studied. However, little has been reported on the regulatory mechanism of sugar signal transduction pathway on metabolism of secondary metabolites. Our previous results indicate that glucose treatments significantly promoted the biosynthesis and accumulation of glucosinolates, and some components of sugar signalling pathway invovled in the regulation of glucosinolates biosynthesis. In the present study, mutants related to glucose signaling and glucosinolates biosynthesis will be used to further determine the components of sugar signaling pathway invovled in the regulation of glucosinolates biosynthesis, and their functions in regulating aliphatic and indole glucosinolate biosythesis by interaction with the transcriptional factors of MYB family. Combined with the genetic analysis, we will aim to elucidate the genetic pathway of the regulation of sugar siganaling on glucosinolates metabolism, and to clarify the molecular mechanism of this regulation. It will provide solid therotical basis for the study of cross-talk of plant signalings and metabolic regulation network of glucosinolates.

芥子油苷是主要存在于十字花科植物中的次生代谢物质，具有重要的生物学功能，如参与植物的防卫反应和抗癌活性等。芥子油苷的代谢是一个非常复杂的过程，受到多种信号的精细调控，关于其代谢调控网络的研究已成为该领域中的一个研究热点。糖信号转导途径是研究得较为透彻的植物信号转导途径之一，它在植物环境适应性和能量中的作用，以及和植物激素等信号之间的互作研究较为深入，但糖信号转导途径对次生代谢物质的调节作用研究未见报道。我们前期研究表明糖处理能显著促进芥子油苷的生物合成与积累，并且发现糖信号转导元件参与对芥子油苷的调控。本项目以模式植物拟南芥为材料，进一步确定糖信号转导途径中参与调节芥子油苷生物合成的元件，以及这些元件通过MYB家族转录因子调控吲哚类和脂肪类芥子油苷的分子机制，结合遗传学分析阐明糖信号途径调控芥子油苷代谢的遗传途径与分子机理。为植物细胞信号之间的互作和芥子油苷的代谢调控网络研究提供理论依据。

芥子油苷（Glucosinolate，GS）及其降解产物不仅是十字花科蔬菜独特风味的来源，也在降低癌症发生率及植物的防卫反应中发挥重要作用。目前，模式植物拟南芥中芥子油苷生物合成的途径已经阐明，其代谢调控网络是当下的研究热点。葡萄糖不仅为植物的生长发育提供基础的能量，同时也作为信号分子调控生命进程。近年来，蔗糖对次生代谢产物花青素生物合成的调控作用已经阐明，但是，糖信号途径与次生代谢产物芥子油苷间的相互作用的机制还鲜有报道。.本研究通过外源施加葡萄糖，结合葡萄糖信号转导和芥子油苷合成相关突.变体，分析了葡萄糖对芥子油苷生物合成调控的机理，同时考察了在此过程中.葡萄糖对硫酸盐的同化和初级硫代谢产物形成的影响。研究取得的主要成果如下：.1、葡萄糖以依赖于葡萄糖信号受体HXK1的方式，通过快速诱导MYB转录因子（主要是MYB28和MYB34）从而调控芥子油苷生物合成相关结构基因的表达，继而促进脂肪类和吲哚类芥子油苷的积累。.2、ABI5在葡萄糖对脂肪类和吲哚类芥子油苷的调控作用中发挥不同的功能。其中，ABI5参与脂肪类和吲哚类芥子油苷的生物合成过程，但是仅仅在葡萄糖对脂肪类芥子油苷的调控作用中发挥作用。.3、葡萄糖可以诱导硫酸盐吸收同化相关基因的表达，从而在硫同化中起到积极的作用；此外，在硫酸盐供应缺乏或充足的培养条件下葡萄糖都可以促进芥子油苷积累，并且半胱氨酸和谷胱甘肽等硫醇类初生代谢产物的含量并没有受抑制，表明葡萄糖通过加强硫同化从而促进芥子油苷的积累，而不是简单的影响硫在初生代谢和次生代谢途径中的分配。. 本项目取得的研究成果不仅有助于深化对芥子油苷代谢调控网络的认识，也为通过代谢工程手段改良十字花科作物中芥子油苷的组分和含量进行作物改良奠定了基础。