Submitted to: Journal of Bacteriology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2002
Publication Date: 4/15/2002
Citation: Kinscherf, T., Willis, D.K. 2002. Global regulation by gida in pseudomonas syringae. Journal of Bacteriology. Interpretive Summary: We are studying the mechanism by which bacteria are able to cause plant disease. Towards this end, we are analyzing the Pseudomonas syringae pv. syringae (the causative agent of brown spot disease of snap bean - an important field disease in Wisconsin) as a model system. We hope to gain an understanding of the molecular biology of the genes and gene products that are required for the disease process. This manuscript describes characterization of the role of the gidA gene in virulence on the plant. The results in this paper are novel and assign a new genetic function to the gidA gene. The analysis of this gene illustrates some of the biological complexity of plant pathogenic bacteria. Ultimately, this understanding will provide information of use to breeders and plant molecular biologists that will enable them to develop plant lines resistant to disease organisms through the alteration of specific plant products that are required by the pathogen.
Technical Abstract: Analysis of two virulence mutants of Pseudomonas syringae B728a revealed that the Tn5 sites of insertion were within the gidA ORF. These mutations were pleiotropic, affecting diverse phenotypes such as lipodepsipeptide (syringomycin and syringopeptin) antibiotic production, swarming, and fluorescent pigment release, as well as virulence. Site- specific recombination of a disrupted gidA gene into the chromosome resulted in the same phenotypic pattern as transposon insertion. Mutant phenotypes were restored by the gidA ORF on a plasmid. The salA gene, a copy number suppressor of the syringomycin deficient phenotype in gacS and gacA mutants, was also found to suppress the antibiotic- negative phenotypes of gidA mutants, suggesting that gidA might play some role in salA regulation. Reporter studies with chromosomal salA- lacZ translational fusions confirmed that salA reporter expression decreased approximately 5-fold in a gidA mutant background, with a concurrent decrease in the expression of the syringomycin biosynthetic reporter fusion syrB-lacZ. Wild-type levels of reporter expression were restored by supplying an intact gidA gene on a plasmid. GidA has often been described as being involved in cell division although most recent evidence suggests a role for the gene in moderating translational fidelity, consistent with the data presented here. The gidA gene is essentially universal in the domains Eubacteriales and Eukaryota but has no counterparts in Archaea, possibly reflecting the fundamental differences known to exist in the translational machinery between the former and latter domains.