P. polymyxa SQR 21与西瓜根际互作机制研究

The preliminary studies showed the strain P. polymyxa SQR-21 was characterized by a highly antagonistic ability against pathogen F. oxysporum f.sp. niveum causing water melon wilt disease. The present project is to study the interaction mechanism of antagonistic microbe P. polymyxa SQR-21 with root exudates of watermelon in the rhizosphere by using a split-root system. Microarray will be applied to clarify the gene regulation characteristics of P. polymyxa SQR-21 during interaction with watermelon root exudates. The genes of P. polymyxa SQR-21 involved in the interactions will be knocked out and their roles will be studied. This work will explore the effect of watermelon root exudates on the colonization of P. polymyxa SQR-21, elucidate the systemic or local effects of P. polymyxa SQR-21 on watermelon plants, and identify the main regutated genes in the interaction. Therefore, the results obtained from the project will provide a scientific basis for the effective use of beneficial rhizosphere microorganisms to overcome the watermelon soil-borne diseases in continuous cropping system.

以具有自主知识产权的显著拮抗西瓜专化型尖孢镰刀菌(F. oxysporum f.sp. niveum)的PGPR菌株P. polymyxa SQR 21为材料，采用分根培养等方法从植物-微生物层面来研究P. polymyxa SQR-21与西瓜根系分泌物的相互影响，运用Microarray等分子生物学技术研究P. polymyxa SQR-21与西瓜根际互作过程中关键调控基因的响应特征，利用突变体验证其与西瓜根际互作中关键调控基因的功能，由此阐明西瓜根系分泌物影响P. polymyxa SQR-21生长和定殖的规律，明确P. polymyxa SQR-21影响西瓜植株系统性或局部性的反应特征，挖掘P. polymyxa SQR-21与西瓜根际互作中的关键调控基因，揭示P. polymyxa SQR-21与西瓜根际的互作机制，为在生物防治西瓜连作生物障碍中科学利用根际有益微生物提供理论依据。

合理施用根际有益菌及其生物肥料是防控作物连作障碍及实现我国化肥减施的有效途径之一。阐明作物-微生物之间“根际对话”机制是科学利用根际有益菌防控作物连作生物障碍的关键。本项目以具有自主知识产权的显著拮抗西瓜专化型尖孢镰刀菌FON的根际有益菌Paenibacilllus polymyxa SQR-21为材料，通过分根培养、色谱鉴定、蛋白质组学及转录组学等方法试图阐明SQR-21与西瓜根际的互作机制，获得了以下主要结果：菌株SQR-21对西瓜根系分泌物中的氨基酸组分具有明显趋化性，外源添加精氨酸、组氨酸和苯丙氨酸可显著促进SQR-21在西瓜根表的定殖。SQR-21定殖西瓜根系后，基础蛋白的分泌量有所减少，而与能量产生、细胞骨架构建及光合作用有关的蛋白分泌量增加，有助于促进植株生长。接种拮抗菌SQR-21或/及枯萎病病原菌FON后西瓜根系蛋白的种类及表达量均发生显著变化。在水培分根系统中，蛋白组及转录组分析表明西瓜接种病原菌FON后其防御相关蛋白的表达出现上调，而宿主的细胞壁结构与物质转运受到破坏，从而导致植株发病；接种拮抗菌SQR-21能诱导宿主抗病相关基因表达，促进物质代谢和转运相关蛋白表达，从而有助于促进植物生长；同时接种FON与SQR-21后西瓜根系与对照相比的差异蛋白主要集中在细胞代谢、调控与转运、防御反应等方面，暗示了SQR-21对FON的拮抗作用。SQR-21定殖后，西瓜根系内表达变化的miRNA基因主要集中在“不同环境微生物代谢”通路上，发现一个仅在SQR-21定殖后表达的新miRNA—novel_19。转录组测序结果表明在体外振荡培养培养和原位接触条件下，西瓜根系均显著调控了SQR-21中碳水化合物转运与代谢、能量产生与转化及转录调控等相关基因，体外条件下根系分泌物还诱导了SQR-21中次级代谢产物合成相关基因的表达，说明SQR-21在与西瓜根系的互作过程中自身代谢及活性物质产生能力均被诱导，有助于其实现根际适应与功能发挥；根表定殖的SQR-21菌体相比于根际与浮游菌体具有更活跃的细胞代谢水平和更强的抗逆性，说明定殖过程赋予了菌体更强的根际适应能力和竞争能力。以上结果有助于深入理解拮抗菌SQR-21与西瓜根系的互作机制，对于在生物防控西瓜连作障碍中科学利用根际有益菌及其生物肥料具有重要指导意义。