SALMONELLA-INDUCED SYSTEMIC ACQUIRED RESISTANCE IN TOMATO AND ITS IMPACT ON SALMONELLA COLONIZATION OF TOMATO LEAVES
Micallef, Shirley A
Salmonella enterica is an enteric human pathogen that lives in gastrointestinal tract; however, Salmonella are able to survive in plants. Thus, vegetables such as tomato are vectors for Salmonella. Evidence suggests that Salmonella induces PAMP-triggered immunity (PTI) in plants, however, plant systemic acquired resistance (SAR), which may act to suppress Salmonella populations, has not been explored. This research investigates whether Salmonella triggers SAR in tomato, and whether SAR activation restricts epiphytic Salmonella populations. Inoculation of tomato leaves with Salmonella increased SAR marker gene expression in distal tomato leaves, but did not reduce populations of the phytopathogen Pseudomonas syringae or Salmonella on distal leaves, even following treatment with chemical SAR activators. NahG plants, which are deficient in SAR signaling, supported higher Salmonella populations, and nitric oxide depletion on leaf surfaces favored Salmonella growth, suggesting that SAR is involved. SAR alone is insufficient to restrict Salmonella growth on tomato, despite being triggered.