Conservation of the lema gene, a virulence regulator from the plant pathogen Pseudomonas syringae, within a human pathogenic bacterium

Abstract

The lemA gene of plant pathogenic strains of Pseudomonas syringae is required for disease lesion formation as well as for production of several phytotoxins and extracellular protease activity. The sequence of this gene places the predicted LemA protein within a family of transmembrane bacterial sensors. The lemA gene is ubiquitous within P. syringae and we have cloned alleles of this locus from P. syringae strains that are pathogenic on bean, tobacco, tomato, oats, coffee, and Arabidopsis thaliana. By Southern blot analysis, we have detected physical homology to the lemA gene within all tested members of the genus Pseudomonas including Pseudomonas aeruginosa. Using an internal restriction fragment of the lemA gene from P. syringae pv. syringae as a probe, we have cloned the P. aeruginosa lemA gene. Surprisingly, the lemA PAO gene complemented the P. syringae pv. syringae lemA mutant strain NUVS1. Introduction of the lemA PAO gene into NUVS1 restored lesion formation on bean, and the production of protease and syringomycin. We are in the process of inactivating this locus in P. aeruginosa strain PAO in order to determine the effect of a lemA mutation on the known virulence factors of this human pathogen. We have also detected homology to the lemA gene in other genera that cause animal disease.