Identification of a Twin-Arginine Translocation System in Pseudomonas syringae pv. tomato DC3000 and Its Contribution to Pathogenicity and Fitness

• Published in: Journal of Bacteriology 2005-12, Vol.187 (24), p.8450-8461
• Main Authors: Bronstein, Philip A, Marrichi, Matthew, Cartinhour, Sam, Schneider, David J, DeLisa, Matthew P
• Format: Article
• Language: English
• Subjects: analysis; Anti-Bacterial Agents; Anti-Bacterial Agents - pharmacology; Arabidopsis; Arabidopsis - microbiology; Arabidopsis thaliana; arginine; Bacteriology; Biological and medical sciences; Biological Transport; biosynthesis; Botany; Copper; Copper - pharmacology; Escherichia coli; Escherichia coli - genetics; Fundamental and applied biological sciences. Psychology; Genes, Reporter; Genetic Complementation Test; genetics; Green Fluorescent Proteins; Green Fluorescent Proteins - analysis; Iron; Iron - metabolism; Lycopersicon esculentum; Membrane Transport Proteins; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; metabolism; Microbiology; Miscellaneous; Molecular Sequence Data; Movement; Mutagenesis, Insertional; mutants; Mutation; Nicotiana - microbiology; Nicotiana benthamiana; Nicotiana tabacum; pathogenicity; Pathogens; pharmacology; phenotype; Phospholipases; Phospholipases - metabolism; physiological transport; Plant Diseases; Plant Diseases - microbiology; Plant Leaves; Plant Leaves - microbiology; Plant Microbiology; plant pathogenic bacteria; Protein Sorting Signals; Pseudomonas syringae; Pseudomonas syringae - genetics; Pseudomonas syringae - pathogenicity; Pseudomonas syringae pv. tomato; Siderophores; Siderophores - biosynthesis; Solanum lycopersicum; Solanum lycopersicum - microbiology; Solanum lycopersicum var. lycopersicum; tobacco; tomatoes; twin-arginine translocation system; virulence; Virulence Factors; Virulence Factors - metabolism
• ISSN: 1098-5530; 0021-9193; 1098-5530; 1067-8832
• DOI: 10.1128/JB.187.24.8450-8461.2005

The bacterial plant pathogen Pseudomonas syringae pv. tomato DC3000 (DC3000) causes disease in Arabidopsis thaliana and tomato plants, and it elicits the hypersensitive response in nonhost plants such as Nicotiana tabacum and Nicotiana benthamiana. While these events chiefly depend upon the type III protein secretion system and the effector proteins that this system translocates into plant cells, additional factors have been shown to contribute to DC3000 virulence and still many others are likely to exist. Therefore, we explored the contribution of the twin-arginine translocation (Tat) system to the physiology of DC3000. We found that a tatC mutant strain of DC3000 displayed a number of phenotypes, including loss of motility on soft agar plates, deficiency in siderophore synthesis and iron acquisition, sensitivity to copper, loss of extracellular phospholipase activity, and attenuated virulence in host plant leaves. In the latter case, we provide evidence that decreased virulence of tatC mutants likely arises from a synergistic combination of (i) compromised fitness of bacteria in planta; (ii) decreased efficiency of type III translocation; and (iii) cytoplasmically retained virulence factors. Finally, we demonstrate a novel broad-host-range genetic reporter based on the green fluorescent protein for the identification of Tat-targeted secreted virulence factors that should be generally applicable to any gram-negative bacterium. Collectively, our evidence supports the notion that virulence of DC3000 is a multifactorial process and that the Tat system is an important virulence determinant of this phytopathogenic bacterium.