Secretome analysis of Pantoea stewartii subsp. stewartii

• Published in: Phytopathology Vol. 94; no. 6
• Main Authors: Tsaltas, D S, Bodman, S V
• Format: Journal Article
• Language: English
• Published: 01.06.2004
• Subjects: Pantoea stewartii
• ISSN: 0031-949X

The phytopathogenic bacterium Pantoea stewartii subsp. stewartii (Pss) is the causal agent of the Stewart's wilt disease in maize. A beetle vector, Chaetocnema pulicaria transmits the disease during periods of feeding directly into the xylem of maize plants. The wilting symptomatology is largely the result of the xylem blockage due to the bacterial secretion of an extracellular polysaccharide (EPS) virulence factor. The EsaI/EsaR quorum sensing (QS) regulatory proteins control EPS synthesis in Pss. A mutation in the esaI gene causes parallel loss of the diffusible inducer N-(3-oxo-hexanoyl)-L-homoserine lactone (AHL), EPS production and virulence. Strains mutated in esaR or esaR and esaI are hypermucoid due to constitutive expression of the EPS biosynthetic pathway. Interestingly the hypermucoid mutant strains are less virulent even though they produce significantly higher amounts of EPS than wild strain DC283. We are analysing the wild and mutant quorum sensing strains for potential differences in their respective secretomes. The rational for this study is that secreted proteins or proteins loosly associated with the membrane surface play a critical role in the infection process, and that some of these proteins are controlled by quorum sensing.