伽师瓜采后链格孢侵染SA介导SAR抗病性机制的研究

Xinjiang is the largest high-quality muskmelon (Cucumis melon L.) origin, planting area in the world. Melon postharvest is easily infected by bacteria and far away from domestic market. As the decay loss is up to 10-30%, melon industry is considered a high-risk business. Therefore, the effective way to control of postharvest disease of melon become the key breakthrough to the development of melon industry. Xinjiang Jiashi melon is extremely resistant to storage (more than 3 month). It is essential for melon to possess disease resistance, excellent storability as well as effective defense system against the pathogen. In the fruther work, Xinjiang Jiashi melon and 86-1 melon are used as experiment material. We will investigate the systemic acquired resistance (SAR) resistance mechanism mediated by salicylic acid (SA) after inoculatied with Alternaria.alternata. High-throughput transcriptome sequencing and quantitative proteomics analysis are applied to construct the differential expression of mRNA and protein in SA mediated SAR resistance mechanism. Moreover, quantitative polymerase chain reaction will be applied to confirm the expression of key genes. Based on physiological experiment, the molecular physiological mechanism about storage stability of Jiashi melon will be investigated from SA mediated SAR resistance experiment. This work will help to understand the endogenous mechanism of pathogen resistance of melon after postharvest. It will provide research foundation to developmen the technology of controlling post-harvest storage diseases and enhancing storage property; it will also provide basis for the resistance prediction and evaluation of breeding after postharvest.

新疆是国内优质厚皮甜瓜的原产地和主产区，但甜瓜采后易受病菌侵染，且远离国内市场，贮运腐烂损失10-30%，产业风险很高，有效控制甜瓜采后病害成为突破产业发展瓶颈的关键。新疆"伽师瓜"极为耐藏（贮期3个月以上），优良的抗病性是耐藏性不可或缺的支撑，伽师瓜应该具备更强的、有效抵抗病菌侵染的防御体系。项目以伽师瓜和86-1甜瓜为实验材料，接种病原菌链格孢，研究侵染后由水杨酸（SA）介导系统获得性抗性（SAR）抗病性机理。通过转录组测序和定量蛋白组技术，比较两种甜瓜链格孢侵染前后SA介导SAR抗病途径基因和蛋白表达差异，qPCR对关键基因表达进行定量分析，结合抗病性生理实验，从SA介导SAR抗病性途径揭示伽师瓜耐藏性的分子生理机制。研究有助于认识甜瓜采后抵抗病原菌侵染的内源机理，为研究甜瓜采后抗病性调控技术和保鲜技术，增强甜瓜耐贮运性提供研究基础；也可为甜瓜采后抗病性预测、评价及抗病育种提供依。

伽师瓜贮藏期长达5-6个月，与其它甜瓜相比，是新疆最耐贮藏的甜瓜品种。项目以伽师瓜（耐藏）和86-1甜瓜（不耐藏）为实验材料，接种链格孢菌，比较两种甜瓜抗病能力的差异，重点对抗病生理、抗病基因克隆与表达、转录组和蛋白组差异开展了研究。伽师瓜和86-1甜瓜接种链格孢，伽师瓜的抗病指数显著高于86-1甜瓜。链格孢侵染引起伽师瓜和86-1甜瓜游离态水杨酸含量的升高，伽师瓜通过提高游离态水杨酸含量并维持在较高水平；对甜瓜PRs基因进行qPCR分析，伽师瓜CHT、GLU基因表达量显著高于86-1甜瓜，且与病斑直径呈正相关，水杨酸和PRs基因在甜瓜抵御链格孢侵染的过程中起到了关键作用。链格孢侵染后，与86-1甜瓜相比伽师瓜ATP消耗较少，H+-ATPase和Ca2+-ATPase响应侵染的时间较早，且活性维持在较高水平；与86-1甜瓜相比伽师瓜PPO、POD和SOD同工酶带颜色较深，且POD和SOD同工酶分别出现1条和4条新带。克隆获得长度为928bp的苯丙氨酸解氨酶基因。贮藏期间86-1甜瓜果皮与果肉病斑直径均大于伽师瓜果皮与果肉，两种甜瓜果肉病斑直径均大于果皮，伽师瓜抵御链格孢侵染的能力强于86-1甜瓜，且果皮抵御能力强于果肉。果实通过调节活性氧代谢抵御链格孢的侵染。伽师瓜和86-1甜瓜转录组，对TF进行预测，注释出59个TF家族，GO注释涉及生物过程中13个条目，涉及细胞组成中8个条目，涉及分子功能中4个条目。对植物抗病基因（PRG），注释出19个结构域，GO注释涉及生物过程中15个条目，涉及细胞组成中14个条目，涉及分子功能中10个条目。伽师瓜和86-1甜瓜蛋白组测序，鉴定蛋白质6568个。蛋白质GO注释涉及生物过程中7316个条目，涉及细胞组成中10601个条目，涉及分子功能中6244个条目。转录组和蛋白组进行表达差异分析，富集到多个水杨酸激素调节、抗病相关的基因与蛋白，这些基因和蛋白在不同侵染阶段和不同品种间表达差异显著，与抗病性密切相关。对采后甜瓜果实抗病性途径的生理机制及分子机制的研究，有助于甜瓜采后抗病育种，为解决长期困扰新疆甜瓜采后病害的问题开辟一个新的技术途径。