Molecular characterization of bacterial antibiosis in the rhizosphere and its impact on Solanaceous plant diseases

由于公众对在环境中使用化学农药和对某些疾病采取的化学控制措施无效感到关切，人们对植物病原体的生物防治日益感兴趣。研究表明，几种拮抗假单胞菌可以在体外或受控条件下利用抗生素控制植物病原菌群。然而，抗生素在土壤中的效率仍然是可变的，这解释了为什么只有少数产生抗菌代谢物的假单胞菌菌株被商业化作为生物农药。本研究以马铃薯和番茄两种茄科植物为研究对象，研究了产抗菌代谢物假单胞菌（Pseudomonas spp.）对引起马铃薯常见结痂的两种重要植物病原菌——疥疮链霉菌（Streptomyces scabiei, Ss）和密歇根键杆菌（Clavibacter michiganensis subsp）的特异性接种效果。引起番茄细菌性枯萎和溃疡病的密歇根菌（Cmm）。本研究的总体目标是在分子水平上了解抗生素如何在根际起作用，它如何影响Ss和Cmm的转录组学，它对病原体定植和感染植物的影响，以及它如何预防疾病。本实验室分离到一株产非那嗪-1-羧酸（PCA）、2,4-二乙酰间苯三酚（DAPG）和氰化氢（HCN）等抗菌代谢物的假单胞菌。这些不能产生抗菌代谢物的菌株的敲除也已被开发出来。这些微生物将用于解决以下具体目标：1)表征与马铃薯和番茄根际假单胞菌抗菌代谢物产生相关的转录活性及其对控制植物病害的影响。2)研究抗菌代谢物产生对Ss和Cmm转录组学的影响。3)确定除抗生素外，抗菌代谢物的产生是否会引发茄科植物的诱导系统性耐药（ISR）。这项创新工作将有助于更好地了解假单胞菌介导的抗生素如何在土壤条件下起作用，以及它如何有助于茄科植物的疾病保护。

An increased interest in biocontrol of plant pathogens has been fuelled by public concern over the use of chemical pesticides in the environment and ineffective chemical control measures against certain diseases. It has been demonstrated that several antagonistic Pseudomonas spp. can control plant pathogen populations under in vitro or controlled conditions using antibiosis. However, the efficiency of antibiosis in soil is still variable, explaining why only few antimicrobial metabolite-producing Pseudomonas spp. strains have been commercialized as biopesticides. Here, it is proposed that two Solanaceous plant species, potato and tomato, be used to study the effect of tailored antimicrobial metabolite-producing Pseudomonas spp. inoculations against two important bacterial plant pathogens: Streptomyces scabiei (Ss) causing common scab of potato and Clavibacter michiganensis subsp. michiganensis (Cmm) causing bacterial wilt and canker of tomato. The general goal of this research is to understand, at the molecular level, how antibiosis operates in the rhizosphere, how it affects the transcriptomics of Ss and Cmm, its effect on colonization and infection of plants by pathogens, and how it can protect against diseases. A collection of Pseudomonas spp. producing antimicrobial metabolites such as phenazine-1-carboxylic acid (PCA), 2,4-diacetylphloroglucinol (DAPG) and hydrogen cyanide (HCN) has been isolated in our laboratory. Knockouts of these strains, incapable of producing the antimicrobial metabolites, have also been developed. These organisms will be used to address the following specific goals: 1) Characterize the transcriptional activity associated with Pseudomonas spp. antimicrobial metabolite production in the rhizosphere of potato and tomato and its impact on controlling plant diseases. 2) Study the impact of antimicrobial metabolite production on Ss and Cmm transcriptomics. 3) Determine if antimicrobial metabolite production can, in addition to antibiosis, trigger induced systemic resistance (ISR) in Solanaceae. This innovative work should lead to a better understanding of how Pseudomonas spp.-mediated antibiosis operates under soil conditions and how it can contribute to disease protection in Solanaceae.