Suppression of Lactuca sativa innate immune response by Salmonella enterica
Date
2019
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Publisher
University of Delaware
Abstract
Plants interact with millions of different organisms in each growing season. The majority of these have no adverse impact on the plant, but certain organisms can be beneficial or detrimental to plant health. When a plant is consumed these bacteria can be taken along with the harvested plant organs and may be ingested or transferred to other un-infested plants. Human enteric pathogens can be also recovered from these contaminated foods, in this thesis we have researched one such bacteria, Salmonella enterica serovar Typhimurium. This common food borne pathogen has been documented as producing disease like symptoms in model and agricultural plants. To evaluate S. Typhimurium on lettuce plants several procedures were used, normal stomatal features were imaged to evaluate S. Typhimurium’s adverse effects on plant innate immunities, and to find the degree that S. Typhimurium can ingress in lettuce possibly prolonging its persistence. We then hypothesized that S. Typhimurium was actively suppressing the innate immunity with SPI1 and or SPI2 when mutants of either failed to suppress plant immunity. Gene expression showed that the ABA pathways were disrupted by unknown proteins in S. Typhimurium. These adverse effects were negated by addition of a root associated plant growth promoting rhizobacteria, which through plant contact can mediate and strengthen plant immune responses to disease and non-pathogenic organisms. Our finding impact issues of contamination in raw leafy greens and novel uses of safe biocontrol techniques that do not require chemicals.