β-氨基丁酸诱导芒果果实抗采后炭疽病的priming机制研究

Resistance induced by elicitors is effective and environment-friendly way of controlling postharvest disease. Upon treatment with some chemical elicitors, the defense reaction in plants can be set to a primed/alarmed state, in which the stronger defense responses will be activated once the plants are infected by pathogens. This type of interaction between host and pathogen is referred to as ‘priming’. Priming of defense has played an important role in induced resistance on harvested fruit, but cell mechanisms of defense priming are poorly understood. Using mango fruit and C. gleosporioides as the interaction system, in this study, the mango fruit will be treated with β-aminobutyric acid (BABA), followed by the inoculation with pathogens. The mode of the defense-related metabolisms and signal hormone molecules contents in fruit will be analyzed, which would be conducive to ascertain the function of priming and resistance-related signal pathway regulated by priming. Furthermore, considering an important role of mitogen-activated protein kinases (MPK) and transcription factors (TFs) in priming-inducing resistance, some molecular technologies including transcriptome sequencing and real-time fluorescent quantitative PCR, yeast one hybrid, yeast two hybrid, bimolecular fluorescence complementation (BiFC) and co-immunoprecipitation (CoIP), etc. will be utilized to explore the gene expression of MPK and TFs, the protein-protein interaction of MPK and TFs, and the regulation of TFs on downstream defense-related genes. The results would provide a theoretical evidence for revealing the regulating mechanisms of priming on BABA-induced resistance in harvested mango fruit.

激发子诱导果蔬产生抗病性是一种环境友好的采后病害控制途径。激发子能刺激植物进入敏感状态，继而对随后发生的病原物侵染表现出强的抗性反应，此过程被称为priming。Priming在激发子诱抗中的意义重大，但目前对其过程的细胞机制尚不明确。本研究以芒果-C. gloeosporioides为互作系统，通过激发子BABA诱导处理，分析果实接种前后的抗病相关代谢和信号激素含量变化，明确priming在诱导果实抗病中的作用及其调控的抗病信号途径；利用转录组测序、RT-qPCR、酵母单/双杂、BiFC、CoIP等分子生物学技术手段，从揭示促分裂原活化蛋白激酶（MPK）和转录因子（TFs）是否参与BABA诱导果实抗病性的priming过程切入，分析MPK和TFs的基因表达变化、二者的蛋白互作以及与MPK互作的TFs对下游抗病基因的调控。为阐明priming调控BABA诱导芒果果实抗病的机制提供理论依据。

激发子诱导果蔬产生抗病性是一种环境友好的采后病害控制途径。激发子能刺激植物进入敏感状态，继而对随后发生的病原物侵染表现出强的抗性反应，此过程被称为“priming”。本项目以芒果—胶孢炭疽菌（Colletotrichum gloeosporioides）为互作系统，通过外源激发子β-氨基丁酸（BABA）诱导处理，分析了芒果果实在接种C. gloeosporioides前后的抗病相关生理代谢、信号激素含量及转录组和蛋白质组的变化。研究结果显示，果实体内苯丙烷代谢相关酶活性、病程相关蛋白水平和总酚、类黄酮、水杨酸、茉莉酸含量在未接种病原菌的24 h内均未明显变化且未受到BABA处理影响；在果实接种病原菌后，上述各项生化参数值均迅速增大，高低顺序依次为BABA+损伤接种 > 清水+损伤接种 > BABA > 清水对照，从而BABA+损伤接种的果实病斑扩展速度低于清水+损伤接种的果实。此外，本研究通过转录组测序筛选出11个差异表达基因并进行qRT-PCR验证，结果表明，芒果果实的过氧化物酶（POD）、几丁质酶（CHT）、肉桂酸脱氢酶（CAD）、半胱氨酸双加氧酶（CDO）、病程相关非表达子（NPR1）、TGA转录因子、WRKY家族转录因子（WRKY23、WRKY47、WRKY75）、促分裂原活化蛋白激酶（MPK20）等的编码基因在BABA处理后第18 h（即接种前6 h）时的表达量轻微上调，使机体进入防御准备状态，且表达量在损伤接种后逐渐增大，以此增强抗病反应。蛋白质组分析结果表明，芒果果实在早期防御准备阶段中，非特异性脂质转移蛋白1（nsLTP）被BABA明显诱导，但下调了UDP-糖基转移酶、翻译激活子GCN1、翻译初始因子3亚基等蛋白，这些在初期阶段受BABA诱导发生的变化可导致弹簧效应，促使priming防御响应过程被激活，表现为在果实接种后有多个逆境响应蛋白受BABA处理而明显上调，如乳胶蛋白样蛋白、病程相关蛋白PR-4和STH-2等；另外BABA诱导的抗性形成过程也涉及水杨酸和Ca2+信号、组蛋白去乙酰化酶等参与的抗病性调节过程。本研究部分揭示了priming在BABA诱导芒果果实抗病中的作用与调控机制，也为更有效地利用BABA激发子提供理论依据。