Dr. Mudgett's laboratory studies the biochemical mechanisms used by bacterial pathogens to alter plant physiology during infection. Extensive genetic and phenotypic data indicate that the bacterial type three secretion (T3S) system and its protein substrates (referred to as T3S effectors) are the major virulence determinants that promote pathogen colonization in plants. The paradigm for T3S effector function has been that these proteins collectively suppress host defense responses to promote colonization and disease progression. The biological function(s) of most T3S effectors, however, is extremely limited and biochemical support for this paradigm is lacking. Thus, the goal of Dr. Mudgett's research has been to elucidate T3S effector function, identify host targets, and provide fundamental knowledge of how perturbation of host signaling pathways leads to bacterial pathogenesis. To do so, the lab studies the T3S effectors in Xanthomonas campestris pathovar vesicatoria (Xcv), the causal agent of leaf spot disease.