活性氧信号介导的枣果实对采后病原菌侵染的抗性响应及调控

Postharvest disease caused by pathogenic infection is the most important casual factor that leads to considerable postharvest decay and loss of fresh jujubes. In our previous research work, the applicant found that "defence ring" resistant tissue surrounding the disease lesion caused by pathogenic infection appeared on the fresh jujube fruit surface during infection, which can effectively restrict the development of lesion and thereby alleviate the degree of disease. "Defence ring" resistant tissue is very typical and unique. This project attempts to comparably study ultra-structure, metabolism of reactive oxygen species (ROS) and accumulation of resistant substance, characteristics of related enzymes and difference of gene expression between tissues from "defence ring", disease lesion and intact fresh jujube fruit during infection. By comparative investigation, this project is designed to reveal change of ultra-structure of "defence ring" tissue, mechanism of ROS burst and its act on transducting message on eliciting resistance, response of metabolism of main resistance substance. Then, mediation of ROS elicited by postharvest pathogenic infection on metabolism of resistance of jujube fruit and their mutual interaction mechanism, and effect of ROS on change of ultra-structure is to be studied. Consequently, the project is to discover mechanism of resistance response of fresh jujube fruit to pathogenic infection (i.e. mechanism of formation of "defence ring" resistant tissue) by studying interaction among different metabolisms during fruit-pathogen mutual-system. Based on the study on mechanism of formation of "defence ring" resistant tissue, regulation of exogenous signals on resistance of fresh jujube fruit and their mechanism are to be explored. The expected results would provide theoretic evidence and reference for techniques for prevention of postharvest disease in fresh jujube fruit.

由病原菌侵染引起的采后病害是导致鲜食枣果实大量腐烂损失的最主要因素。申请人前期研究发现，鲜枣果实在受到病原菌侵染时会在病斑周围形成"防御环"抗性组织，有效地抑制病斑的扩展，减轻病害。"防御环"现象极为典型独特。本项目拟在病原菌侵染过程中，比较分析鲜枣果实"防御环"组织、病灶组织、正常组织三者的超微结构、活性氧代谢和抗性物质积累、相关酶特性及基因表达差异。通过比较研究，明确鲜枣果实"防御环"抗性组织的超微结构变化规律、活性氧信号的激发机理与传导模式、关键抗性物质代谢的响应机制。然后，研究病原菌侵染激发的活性氧信号对抗性代谢的介导与互作机制、对超微结构变化的作用机制。通过研究果实-病原菌互作体系中不同代谢之间相互作用，最终阐明鲜枣果实对病原菌侵染的抗性响应机制（即"防御环"抗性组织形成机制）。基于"防御环"形成机制，探索果实抗性的外源信号调控机理，为防治果实采后病害提供理论依据和技术参考。

由病原菌侵染引起的采后病害是导致鲜食枣果实大量腐烂损失的最主要因素。本项目前期研究发现，鲜枣果实在受到病原菌侵染时会在病斑周围形成“防御环”抗性组织，有效地抑制病斑的扩展，减轻病害的发生。本项目通过研究明确了链格孢菌侵染过程中鲜枣果实“防御环”形成的规律与条件，揭示了“防御环”形成过程中枣果皮超微结构变化规律。通过RNA-seq测序分析明确了鲜枣-链格孢菌互作过程中枣抗性相关基因转绿组表达差异，并进行了验证，确定了活性氧代谢和抗性物质积累代谢途径在“防御环”形成过程在重要作用，初步明确了活性氧信号作用。通过苯丙烷抗性物质代谢分析和功能验证，确定了对香豆酸及其酯类物质在鲜枣果实抗病过程“防御环”形成中的作用。利用外源SA、BABA处理可激发活性氧信号在鲜枣-链格孢菌互作过程中的作用，从而起到诱导枣果实抗病性增强和促进“防御环”形成，起到抑制病害扩展的作用。利用外源对香豆酸及其酯类处理，可明显诱导鲜枣果实抗病性的产生，抑制多种采后病害的发生。外源对香豆酸及其酯类处理还能直接抑制链格孢菌的生长繁殖。本研究发现，外源对香豆酸及其酯类对链格孢菌质膜系统的结构和功能具有直接的破坏作用，从而增加胞内离子及大分子物质的渗漏，刺激胞内活性氧大量产生并产生脂质过氧化反应。在本项目的实施过程中，发表论文6篇，获得授权专利2项，进行了科普和应用推广，取得了一定的生产实际效果。总之，基于鲜枣“防御环”形成机制，探索果实抗性的外源信号调控机理，为防治果实采后病害提供理论依据和实践应用技术参考。