Signal transduction in plant-beneficial rhizobacteria with biocontrol properties.
Biological control of root pathogens--mostly fungi--can be achieved by the introduction of selected bacterial inoculants acting as 'biopesticides'. Successful inoculants have been identified among Gram-negative and Gram-positive bacteria, often belonging to Pseudomonas spp. and Bacillus spp., respectively. Biocontrol activity of a model rhizobacterium, P. fluorescens CHAO, depends to a considerable extent on the synthesis of extracellular antimicrobial secondary metabolites and exoenzymes, thought to antagonize the pathogenicity of a variety of phytopathogenic fungi. The regulation of exoproduct formation in P. fluorescens (as well as in other bacteria) depends essentially on the GacS/GacA two-component system, which activates a largely unknown signal transduction pathway. However, recent evidence indicates that GacS/GacA control has a major impact on target gene expression at a post-transcriptional level, involving an mRNA target sequence (typically near the ribosome binding site), two RNA binding proteins (designated RsmA and RsmE), and a regulatory RNA (RsmZ) capable of binding RsmA. The expression and activity of the regulatory system is stimulated by at least one low-molecular-weight signal. The timing and specificity of this switch from primary to secondary metabolism are essential for effective biocontrol.
Haas
Dieter
D
Laboratoire de Biologie Microbienne, Université de Lausanne, Switzerland. Dieter.Haas@lbm.unil.ch
Keel
Christoph
C
Reimmann
Cornelia
C
D000898:Antibiosis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D005658:Fungi / Q000254:growth & development; D010572:Pest Control, Biological; D010935:Plant Diseases / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology*; D011551:Pseudomonas fluorescens / Q000254:growth & development* / Q000378:metabolism; D015398:Signal Transduction
D001426:Bacterial Proteins