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Poster: Molecular & Cellular Plant-Microbe Interactions: Biochemistry & Cell Biology


Examining putative motility genes in Clavibacter michiganensis subsp. michiganensis.
C. PERITORE (1), M. Tancos (2), C. Smart (2) (1) Cornell University, U.S.A.; (2) Cornell University, U.S.A.

The Gram-positive bacterium Clavibacter michiganensis subsp. michiganensis (Cmm) is the causative agent of bacterial canker of tomato (Solanum lycopersicum). Cmm historically has been characterized as a non-motile pathogen, however, it is known to move acropetally and basipetally in the xylem of infected plants. Under artificial xylem conditions in microfluidic chambers, non-flagellated Cmm actively moved against the media flow at ~6 ┬Ám/minute; these speeds were similar to those observed in planta. We have hypothesized that Cmm uses a type IV pilus (Tfp) mediated motility system similar to that of Xylella fastidiosa. Tfp are diverse in that biosynthesis can be mediated by pil, com, and/or tad operons in both Gram-negative and positive bacteria. Two tight adhesion (tad) operons have been identified through sequence similarity in the annotated genome of Cmm, and literature suggests they may play a crucial role in biosynthesis of Tfp. Cmm transformants were generated by disrupting the tad operon promoter. Microfluidic chambers will be utilized to mimic in planta conditions of xylem flow to assay and compare motility between mutants and wildtype. Genetic and microscopic studies will be complemented with in planta virulence assays to investigate the role of tad genes in the Cmm-tomato pathosystem. Understanding how the pathogen infects and moves in the plant will strengthen our biological knowledge of Cmm, possibly leading to novel disease control strategies.