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Effects of galU Mutation on Pseudomonas syringae--Plant Interactions

September 2010 , Volume 23 , Number  9
Pages  1,184 - 1,196

Wen-Ling Deng,1 Yuan-Chun Lin,2 Rong-Hwa Lin,3,4 Chia-Fong Wei,2 Yi-Chiao Huang,2 Hwei-Ling Peng,4 and Hsiou-Chen Huang2

1Department of Plant Pathology, 2Graduate Institute of Biotechnology, and 3Biotechnology Center, National Chung Hsing University, Taichung, 40224, Taiwan; 4Department of Biological Science and Technology, National Chiao Tung University, Hsin Chiu 30050, Taiwan

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Accepted 3 May 2010.

Bacterial galU coding for a uridine diphosphate-glucose pyrophosphorylase plays an important role in carbohydrates biosynthesis, including synthesis of lipopolysaccharides (LPS), membrane-derived oligosaccharides, and capsular polysaccharides. In this study, we characterized the galU mutant of Pseudomonas syringae pv. syringae 61 (Psy61), a necrotizing plant pathogen whose pathogenicity depends on a functional type III secretion system (T3SS), and showed that the Psy61 galU mutant had reduced biofilm formation ability, was nonmotile, and had an assembled T3SS structure but failed to elicit hypersensitive response in resistant plants and necrotic lesions in susceptible plants. Moreover, the defective LPS and other pathogen-associated molecular patterns (PAMPs) on the surface of the Psy61 galU mutant were capable of inducing PAMP-triggered immunity, which severely compromised the ability of the Psy61 galU mutant to survive in planta. Our results demonstrated that the complete LPS protected plant-pathogenic bacteria from host innate immunity, similar to what was found in animal pathogens, prior to the translocation of T3S effectors and bacterial multiplication.

© 2010 The American Phytopathological Society