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A Metabolic Regulator Modulates Virulence and Quorum Sensing Signal Production in Pectobacterium atrosepticum

March 2013 , Volume 26 , Number  3
Pages  356 - 366

Marion F. Cubitt,1,2 Peter E. Hedley,2 Neil R. Williamson,1 Jenny A. Morris,2 Emma Campbell,2 Ian K. Toth,2 and George P. C. Salmond1

1Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QW, U.K.; 2Cell and Molecular Sciences, James Hutton Institute, Invergowrie, Dundee DD2 5DA, U.K.

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Accepted 24 October 2012.

Plant cell wall–degrading enzymes (PCWDE) are key virulence determinants in the pathogenesis of the potato pathogen Pectobacterium atrosepticum. In this study, we report the impact on virulence of a transposon insertion mutation in the metJ gene that codes for the repressor of the methionine biosynthesis regulon. In a mutant strain defective for the small regulatory RNA rsmB, PCWDE are not produced and virulence in potato tubers is almost totally abolished. However, when the metJ gene is disrupted in this background, the rsmB phenotype is suppressed and virulence and PCWDE production are restored. Additionally, when metJ is disrupted, production of the quorum-sensing signal, N-(3-oxohexanoyl)-homoserine lactone, is increased. The metJ mutant strains showed pleiotropic transcriptional impacts affecting approximately a quarter of the genome. Genes involved in methionine biosynthesis were most highly upregulated but many virulence-associated transcripts were also upregulated. This is the first report of the impact of the MetJ repressor on virulence in bacteria.

© 2013 The American Phytopathological Society