Congratulations to Kim; her paper was accepted for publication in Scientific Reports today! This is the next chapter in our investigation of how plant disease influences the outcomes of leaf epiphytes. This study investigated the interaction between 3 organisms: Salmonella enterica, the phytopathogenic bacterium Xanthomonas hortorum pv. gardneri, and the tomato plant host. Previously, we found that X. gardneri promotes S. enterica survival on the inhospitable niche of the tomato leaf. Here, we demonstrate that the X. gardneri transcription activator-like effector AvrHah1 is both necessary and sufficient for this beneficial effect on S. enterica. An X. gardneri avrHah1 mutant loses the ability to increase S. enterica persistence, and addition of avrHah1 to X. vesicatoria, a Xanthomonad that is typically unable to benefit S. enterica in this environment,
provides a gain of function. In addition, we begin to characterize the mechanism of AvrHah1 function in S. enterica persistence by examining the plant immune response and measuring cellular damage that occurs during disease. The knowledge gained through this study offers a better understanding of how an inhospitable environment changes during infection and provides
information regarding how these changes alter this niche to one that is conducive to S. enterica survival.