Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2022
Publication Date: 5/4/2022
Citation: Cowles, K.N., Block, A.K., Barak, J.D. 2022. Xanthomonas hortorum pv. gardneri TAL effector AvrHah1 is necessary and sufficient for increased persistence of Salmonella enterica on tomato leave. Scientific Reports. 12, 7313. https://doi.org/10.1038/s41598-022-11456-6
DOI: https://doi.org/10.1038/s41598-022-11456-6

Interpretive Summary: Food borne pathogens such as Salmonella are a recurrent problem for agriculture due to their potential impact on human health and the resultant need for monitoring and recalls of food products that contain them. One approach to mitigate this problem, particularly in plant based foods, is to reduce the ability of Salmonella to live and propagate on the plants. Recent studies have shown that growth of Salmonella on plants such as tomato is enhanced in the presence of specific plant pathogens. In this study researchers from the University of Wisconsin-Madison, in collaboration with ARS scientists at the Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, Florida have identified a protein for plant pathogenic bacteria that promotes the growth of Salmonella on tomato plants. This research increases the understanding of how Salmonella can grow in plants and can help inform mitigation efforts to limit Salmonella contamination of human food supplies.

Technical Abstract: Enteric human pathogens such as Salmonella enterica are ubiquitous in the plant environment, persisting in the face of UV stress, plant defense responses, desiccation, and nutrient limitation. These fluctuating conditions of the leaf surface result in decline of S. enterica populations. Biomultipliers, such as the phytopathogenic bacterium Xanthomonas gardneri, alter the phyllosphere to the benefit of S. enterica. The specific X. gardneri-dependent changes to this niche that promote S. enterica persistence remain unclear, and this work focuses on identifying factors that lead to increased S. enterica survival on leaves. Here, we show that the X. gardneri transcription activator-like effector AvrHah1 is both necessary and sufficient for increased survival of S. enterica on tomato leaves. An X. gardneri avrHah1 mutant fails to influence S. enterica survival while addition of avrHah1 to X. vesicatoria provides a gain of function. Our results indicate that although X. gardneri stimulates a robust immune response from the plant, AvrHah1 is not required for these effects. In addition, we demonstrate that cellular leakage that occurs during disease is independent of AvrHah1. Investigation of the interaction between S. enterica, X. gardneri, and the plant host provides information regarding how an inhospitable environment changes during infection.