水杨酸、茉莉酸和乙烯处理对柑橘果实抗病反应中水杨酸信号途径的调控机制

Postharvest fungal diseases, for example the citrus green mold, cause the greatest losses during the postharvest storage and transportation of citrus fruit. Control of these fungi is mostly based on the use of chemical fungicides, such as imazalil, thiabendazole, pyrimethanil, prochloraz, fludioxonil and so on. Given the toxicity of fungicides on the environment and in humans, as well as the development of fungicide resistance by pathogens, considerable effort has been made to develop alternative methods for the control of the disease. As a lasting and broad-spectrum resistance to pathogenesis, inducing systemic resistance of organism to pathogen can be a new method to relieve losses caused by citrus disease. Previous studies have shown that application of exogenous salicylic acid (SA), jasmonic acid (JA) or ethylene (ET) to some plants can induce systemic resistance to pathogenesis, and SA pathway play a critical role in plant disease resistance. In order to reveal the regulation mechanism of several hormones on salicylic acid signaling pathway in citrus fruit disease resistance, this research will evaluate the effect of SA, JA and ET treatments on green mold and compare their ability to induce resistance on citrus fruits. Meanwhile, the key genes and proteins, which are correlated to SA signal pathways in SA-, JA- and ET- treated fruit, will be screened by transcriptomic and proteomic technologies. On the basis of this, the effect of SA, JA and ET treatments on the key genes and key enzymes, which are associated with SA biosynthesis, SA conversion, signal recognition and transduction in citrus fruit were analyzed. The results of this project will provide theoretical basis and technical support for the development of new citrus disease control technologies based on induction of disease resistance.

以绿霉病为代表的侵染性病害是造成柑橘果实采后损失的最大原因，生产上常使用化学杀菌剂如抑霉唑、噻菌灵、嘧霉胺、咪鲜胺和咯菌腈等控制该病害，随着人们对食品安全的日渐关注，寻找安全高效的病害控制方法成为亟需解决的问题。诱导抗病性具有持久和广谱性，可以做为柑橘果实病害控制的新思路。水杨酸（SA）、茉莉酸（JA）和乙烯（ET）等植物激素处理能诱导一些植物产生抗病性，同时，在植物抗病反应中SA信号途径发挥着非常重要的作用。本项目拟通过研究SA、JA和ET处理对柑橘果实绿霉病发病情况的影响，在组学研究基础上筛选三种外源激素处理后柑橘果实抗病反应中与SA信号途径相关的重要基因和蛋白，进一步研究内源SA合成与转化、识别与信号传导相关基因、蛋白表达和酶活性变化。以此揭示几种激素对柑橘果实抗病反应中SA信号途径的调控机制。本项目的研究结果将为开发基于诱导抗病性的新型柑橘果实病害防治技术提供思路和途径。

柑橘果实在采后流通中的最大问题是以绿霉病为主的侵染性病害，阐明其抗病机制对于明确植物-病原菌互作机制从而指导生产实践具有重要意义。本项目以不同浓度水杨酸（SA）、茉莉酸（JA）和乙烯（ET）处理柑橘果实，利用组学技术研究不同外源激素处理对柑橘果实抗病反应中相关基因的系统水平影响，进一步研究三种外源激素对柑橘果实抗病反应中内源SA合成及转化途径、内源SA信号转导途径的影响，并对外源SA诱导后CsWRKY70的转录调控机制进行了分析。研究结果表明，采用2 mM SA、0.2 mM JA以及1.5 mM ET处理均能显著降低柑橘果实采后绿霉病的发病率和病斑直径。RNA-seq分析表明，侵染后期（48 h），三种激素处理中与PTI（Pathogen triggered immunity）和ETI（Effector triggered immunity）相关的基因均显著上调表达。SA和ET处理诱导了柑橘果实中内源SA的积累，JA处理抑制了两种形式SA的积累。同时，外源SA和ET处理激活了SA信号转导相关基因NPR1、TGA和PR1的表达，JA处理则抑制了它们的表达，表明外源SA和ET处理对内源SA合成转化及信号传递有诱导作用，JA处理则会抑制内源SA合成及信号传递。此外，SA诱导的转录因子CsWRKY70可以转录激活MeSA合成相关基因CsSAMT1和CsSAMT2的表达，进而积极调控柑橘果实采后抗病性。研究结果将为进一步解析柑橘果实抗病机制，进而从诱导抗病性角度控制病害发生提供理论依据。