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Poster: Molecular & Cellular Plant-Microbe Interactions: MPMI


Determining the genetic basis for stomatal aperture modulation by Salmonella enterica serovar Typhimurium strain 14028.
J. MONTANO (1), S. Porwollik (2), M. McClelland (2), M. Melotto (1) (1) Department of Plant Sciences, University of California, Davis, U.S.A.; (2) Department of Microbiology and Molecular Genetics, University of California, Irvine, U.S.A.

Pathogens that cause foodborne illness pose a challenge to food safety and security, as crops that are vectors for these human diseases may appear healthy, resulting in their integration to marketplaces throughout the world. Although some human pathogens that are introduced to the phyllosphere elicit an immune response within the plant, Salmonella enterica serovar Typhimurium strain SL1344 has been shown to disrupt plant innate immune signaling (including stomatal immunity) and survive for long periods of time inside the leaf. We have determined that, like SL1344, S. enterica serovar Typhimurium strain 14028 (14028) also disrupts stomatal immunity after 4 hours post-inoculation (hpi). We set up a genetic screen to elucidate the mechanism(s) by which 14028 modulates stomatal movement using a mutant library with high-coverage and multi-gene deletions created with lambda-red mediated gene-replacement. Leaf sections of lettuce (Lactuca sativa cultivar Salinas) were floated on bacterial inoculum (108 CFU/mL) or a water control under light and stomatal aperture widths were measured via microscopy at 4 hpi. A total of 535 mutants were analyzed for their inability to stimulate stomatal opening at 4 hpi and compared to the wild type and water control. We observed that mutant strains lacking operons involved in secretion could not open stomata. Further characterization of identified mutants will aim to determine the individual genes that are pertinent for stomatal opening.