Involvement of sensor kinase gene (skrp 1122) for biocontrol activity by Pseudomonas synxantha BG33R

• Published in: Phytopathology Vol. 98; no. 6; p. S52
• Main Authors: Fang, G, Waldrop, V C, Wechter, W P, Kluepfel, DA
• Format: Journal Article
• Language: English
• Published: 01.06.2008
• Subjects: Magnaporthe grisea; Nematoda; Oomycetes; Oryza sativa; Pseudomonas
• ISSN: 0031-949X

Previous research identified Pseudomonas synxantha BG33R as potential carrier for a nematode egg-kill factor. Further research indicated that BG33R exhibits a broad-spectrum of antagonistic activity against oomycetes, fungi, nematodes and insects. Earlier screening for negative egg-kill factor indicated the presence of a GacS sensor kinase gene regulating pleiotropic traits (skrp1122) was necessary for the biocontrol activity. Sequencing the skrp1122 locus revealed a co-lineage of its putative cognate partner, a response regulator GacA homolog, and multiple genes involved in membrane transportation. Functional analysis of the skrp1122-negative disruption mutant revealed a pleiotropic defect for most biocontrol activities and altered colony morphology. The impaired antimicrobial activity against Magnaporthe grisea of the skrp1122 (-) mutant was carefully examined. The mutant was no longer able to suppress vegetative growth, conidiation, and appressorium formation of the fungus, nor was it able to protect rice plants from rice blast disease. Our results indicate an essential role of the GacS/GacA two-component system in the biocontrol activity in this organism.