LuxS/AI-2群体感应系统在胡萝卜果胶杆菌巴西亚种对黄瓜致病进程中的调控机理研究

LuxS/AI-2 quorum sensing (QS) system plays a significant role in terms of regulating the pathogenicity, signal conduction and environmental adaptability in various pathogens and plays a crucial role in interaction of pathogen and plant. Pectobacterium carotovorum subsp. brasiliense (Pcb) SX309 is a pathogen that could cause bacterial stem soft rot in cucumber and has a wide host range. Moreover, the severity of soft rot is positively correlated to Pcb population density. Genome sequence analysis showed that Pcb SX309 has the LuxS/AI-2 QS system and previous research in strain SX309 indicated that LuxS/AI-2 QS system is related to pathogenicity. In this study, we will disrupt luxS gene which is response to AI-2 signal synthesis, and then analyze the regulatory mechanism of LuxS/AI-2 QS system to Pcb virulence. Simultaneously comparative transcriptome analysis will be performed to investigate the regulation relationship of LuxS/AI-2 and CarI/AHLs QS system by results of compared transcriptome changes among Pcb, Pcb△luxS and Pcb△carI mutant strains. In addition, we will focus on the effect of LuxS/AI-2 QS system on cucumber endophytic bacteria community by high-throughput sequencing and molecular ecology methods. The aim of this study is to clarify the regulation of LuxS/AI-2 QS system in Pcb strain intraspecies and interspecies during cucumber soft rot formation. These results of this project are helpful to explore a new method to interfere with the regulatory mechanism of LuxS/AI-2 system and to provide a theoretical basis for developing new control strategies.

LuxS/AI-2群体感应系统对多种病原菌的致病功能、信号交流及环境适应性具有重要调控作用。胡萝卜果胶杆菌巴西亚种 (Pectobacterium carotovorum subsp. brasiliense, Pcb) 引起黄瓜细菌性茎软腐病，该菌具有广泛的寄主范围，且Pcb群体密度与茎软腐病形成呈正相关。本项目通过定位突变luxS基因研究LuxS/AI-2系统对Pcb致病力的分子调控机制，利用比较转录组学研究LuxS/AI-2和CarI/AHLs系统在Pcb使黄瓜致病过程中对致病力的调控机理，并采用高通量测序结合分子生态学方法分析LuxS/AI-2系统在Pcb致病进程中对黄瓜内生细菌群落的影响。通过本课题的研究，将阐明在Pcb对黄瓜致病进程中LuxS/AI-2系统对Pcb自身和对其他细菌的调控机制，有助于提出干扰LuxS/AI-2系统调控机制的新方法，为开发新的控害策略提供理论依据。

LuxS/AI-2群体感应系统对多种病原菌的致病功能、信号交流及环境适应性具有重要调控作用。胡萝卜果胶杆菌巴西亚种 (Pectobacterium carotovorum subsp. brasiliense, Pcb) 引起黄瓜细菌性茎软腐病，该菌具有广泛的寄主范围，且Pcb群体密度与茎软腐病形成呈正相关。通过本课题研究，完成了胡萝卜果胶杆菌巴西亚种SX309全基因组测序，分析了与致病力和寄主遗传适应性相关的因子，将有利于系统研究果胶杆菌中毒力基因及其寄主遗传适应分子机制和致病机理。筛选了胡萝卜果胶杆菌巴西亚种SX309侵染黄瓜过程中最适内参基因并加以应用，为进一步阐明黄瓜-Pcb相互作用的分子机制提供了必要的参考。通过基因敲除和细菌转录组测序分析，初步揭示LuxS/AI-2 QS系统对Pcb菌株致病力和寄主适应性的调控机制。通过互作转录组测序分析，揭示Pcb侵染黄瓜发病过程中，植物的防御机制和Pcb的致病机制之间的相关性，为解析黄瓜细菌性茎软腐病呈“爆发式”发生的根本原因提供了依据。