Whole Genome Analyses of Clavibacter michiganensis subsp. michiganensis Strains Reveals Core Secreted Proteins that Promote Virulence on Tomato
S. THAPA (1), R. Gilbertson (1), G. Coaker (1) (1) University of California, U.S.A.

Clavibacter michiganensis subsp. michiganensis (Cmm) is a gram positive actinomycete causing bacterial canker of tomato. In this study, we determined the complete genome sequence of 11 California Cmm strains and one saprophytic Clavibacter strain using a combination of Illumina and PacBio sequencing. When compared to the reference strain NCPPB382, we detected significant alterations in California strains with respect to plasmid number, plasmid composition, and genomic island presence. The pCM2 plasmid, that was previously demonstrated to be required for NCPPB382 virulence, also differs in presence and gene content across Cmm strains. pCM2 is absent in some Cmm strains and that still retain virulence on tomato. We have identified 16 core secreted proteins present across pathogenic Cmm strains. The core secretome includes proteases and degradative enzymes. Deletion of the core secreted pelA1 pectate lyase in the California strain CASJ002 reduces bacterial virulence on tomato. However, deletion of the closely related pelA2 has no effect. Consistent with these observations, pelA1 expression is strongly induced in xylem mimicking media. Functional analyses of additional core secretome members will also be presented. Analyses of the finished genomes from California Clavibacter strains has provided insight into genome organization, genomic differences between pathogenic and saprophytic Clavibacter strains, and highlighted conserved candidate virulence genes.

Abstract Number: P11-381
Session Type: Poster