Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2008
Publication Date: 11/1/2008
Citation: Jahn, C.E., Willis, D.K., Charkowski, A.O. 2008. Contribution of Flagellar Sigma Factor (FliA) to Virulence of Dickeya dadantii. Molecular Plant-Microbe Interactions. 21(11)1431-1442. Interpretive Summary: We are studying the mechanism by which bacteria are able to cause plant disease. The enteric phytopathogen Dickeya dadantii causes wilting and soft rot in a wide range of plants, including many weed species, ornamental plants, and economically important crops. D. dadantii produces of a variety of cell wall-degrading enzymes, such as pectate lyases and cellulases, that cause tissue maceration and these enzymes are the primary pathogenicity factor of this enterobacterium. We hope to gain an understanding of the molecular biology of the genes and gene products that are required for the disease process by the bacteria. Ultimately, this understanding will provide information of use to breeders and plant molecular biologists that will enable the development of plant lines resistant to disease organisms. This manuscript describes the mutational analysis of virulence in D. dadantii. A surprising finding was that a new regulatory gene (fliA) was required for full virulence of this pathogen on host plants. Because this gene is a key contributor to virulence in D. dadantii, it is being looked into as a new target for disease control.
Technical Abstract: The ability to move in a directed manner affords advantages to host-adapted bacteria including the ability to move toward a preferred host, access to infection sites, and escape back into the environment. The best understood flagella regulatory pathways are the transcriptional hierarchies of Escherichia coli and Salmonella Typhimurium. However data from other bacterial species suggest that the regulatory cascades and environmental effects on flagella gene expression cannot be generalized. The genome sequence of the enteric phytopathogen Dickeya dadantii (formerly Erwinia chrysanthemi) revealed homologs of all flagella genes, but arrangement of the operons differs from other enterobacteria. We found that FliA, the alternate sigma factor required for flagella production, also affects pectate lyase production and is required for full virulence and for biofilm formation. FliA did not affect production of other cell wall degrading enzymes, including cellulases, polygalacturonases, and proteases. Because FliA is a key contributor to virulence in D. dadantii, it is a new target for disease control.