Plant immunity against human pathogens
M. MELOTTO (1). (1) University of Texas-Arlington, Arlington, TX, U.S.A.
Enterohemorrhagic <i>Escherichia coli</i> and <i>Salmonella enterica</i> appear to be the most common causal agents of food poisoning associated with the consumption of fresh leafy vegetables. These human pathogens are not proven to be plant pathogens yet. Nonetheless, under certain conditions these bacteria can survive on and penetrate into plant tissues causing serious food borne disease outbreaks. In this study, we sought to identify components of the plant immunity system that are regulated in the presence of either <i>E. coli</i> O157:H7 or <i>S. enterica</i> serovar Typhimurium SL1344. During the epiphytic phase, O157:H7 induces strong and lasting stomatal closure, whereas SL1344 induces a transient closure in both the model plant Arabidopsis and lettuce. These findings raise the possibility that not only plant pathogens (some pathovars of <i>Pseudomonas syringae</i> and <i>Xanthomonas campestris</i>), but also some human pathogens (SL1344) have evolved mechanisms to subvert stomatal defense to enter plant tissues and survive endophytically. It is equally possible however, that SL1344 is able to evade recognition by the plant immune system. Using high throughput technologies, we have also observed that SL1344 does not induce very strong apoplastic immunity as compared to O157:H7. Recent results highlighting the differential plant responses induced by these two human pathogens will be discussed.
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