Impact of Type VI Secretion System (T6SS) effectors on Arabidopsis thaliana transformation in A. tumefaciens
J. BRAVO (1), A. Kenefick (2), B. Nguyen (2), J. Kim (2), R. Froom (2), A. Resnick (2), L. Banta (2) (1) Williams College, U.S.A.; (2) Williams College, U.S.A.

In A. tumefaciens, as in several other bacteria species, the recently discovered type VI secretion system (T6SS) releases effectors that act as toxins in inter- and intra-bacterial competition.  However, the contribution of the A. tumefaciens T6SS to virulence is not yet well understood.  We discovered that Arabidopsis thaliana stem infections with agrobacteria lacking the T6SS resulted in the formation of fewer tumors than infections with wild type bacteria.  This and other previous data have led us to hypothesize that the T6SS may dampen A. thaliana defenses, but in so doing, may inadvertently elicit host defenses as well.  Using bacterial mutants deficient in one or more of the known T6SS effectors, we have begun to characterize the contributions of individual effectors to the attenuation and/or triggering of host responses.  We have found that the T6SS impacts transient transformation as well as tumorigenesis. Other host responses that are altered include defense-related gene expression and resistance to subsequent infection by Pseudomonas syringae pv. maculicola.  Finally, further investigations with mutant plant lines have revealed insights into the particular host defense pathways that may be modulated by the T6SS. 

Abstract Number: P9-242
Session Type: Poster