To establish host association, the innate immune system, which is one of the first lines of defense against infectious disease, must be circumvented. Plants encounter enteric foodborne bacterial pathogens under both pre- and post-harvest conditions. Human enteric foodborne pathogens can use plants as temporary hosts. This unique interaction may result in recalls and illness outbreaks associated with raw agricultural commodities. The purpose of this study was to determine if Salmonella enterica Typhimurium applied to lettuce leaves can suppress the innate stomatal defense in lettuce and utilization of UD1022 as a biocontrol against this ingression. Lettuce leaves were spot inoculated with S. Typhimurium wild type and its mutants. Bacterial culture and confocal microscopy analysis of stomatal apertures were used to support findings of differences in S. Typhimurium mutants compared to wild type. The persistence and internalization of these strains on lettuce was compared over a 7-day trial. S. Typhimurium may bypass the innate stomatal closure defense response in lettuce. Interestingly, a few key T3SS components in S. Typhimurium were involved in overriding stomatal defense response in lettuce for ingression. We also show that the T3SS in S. Typhimurium plays a critical role in persistence of S. Typhimurium in planta. Salmonella populations were significantly reduced in all UD1022 groups by day 7 with the exception of fliB and invA mutants. Salmonella internalization was not detected in plants after UD1022 treatment and had significantly higher stomatal closure rates (aperture width = 2.34 μm) by day 1 compared to controls (8.5 μm). S. Typhimurium SPI1 and SPI2 mutants showed inability to reopen stomates in lettuce suggesting the involvement of key T3SS components in suppression of innate response in plants. These findings impact issues of contamination related to plant performance and innate defense responses for plants.

中文翻译：

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生菜上沙门氏菌逃避植物先天防御反应。

为了建立宿主关联，必须规避先天免疫系统，它是抵御传染病的第一道防线之一。植物在收获前和收获后都会遇到肠道食源性细菌病原体。人类肠道食源性病原体可以利用植物作为临时宿主。这种独特的相互作用可能会导致与农产品原料相关的召回和疾病爆发。本研究的目的是确定应用于生菜叶子的鼠伤寒沙门氏菌是否可以抑制生菜的先天气孔防御，并利用 UD1022 作为针对这种侵入的生物防治方法。用鼠伤寒沙门氏菌野生型及其突变体对生菜叶进行点接种。使用细菌培养和气孔孔径的共聚焦显微镜分析来支持鼠伤寒沙门氏菌突变体与野生型相比的差异的发现。在为期 7 天的试验中比较了这些菌株在生菜上的持久性和内在化。鼠伤寒沙门氏菌可能绕过生菜先天的气孔关闭防御反应。有趣的是，鼠伤寒沙门氏菌中的一些关键 T3SS 成分参与了生菜入侵的压倒性气孔防御反应。我们还表明，鼠伤寒沙门氏菌中的 T3SS 对于鼠伤寒沙门氏菌在植物中的持久存在起着至关重要的作用。到第 7 天，所有 UD1022 组中的沙门氏菌数量均显着减少，但 fliB 和 invA 突变体除外。UD1022 处理后，植物中未检测到沙门氏菌内化，并且与对照 (8.5 μm) 相比，第 1 天气孔闭合率 (孔径宽度 = 2.34 μm) 显着更高。鼠伤寒沙门氏菌 SPI1 和 SPI2 突变体表现出无法重新打开生菜中的气孔，这表明关键的 T3SS 成分参与了植物先天反应的抑制。这些发现影响了与植物性能和植物先天防御反应相关的污染问题。