Boyce Thompson Institute for Plant Research, Ithaca, NY 14853, USA.
Environ Microbiol. 2013 Sep;15(9):2418-30. doi: 10.1111/1462-2920.12113. Epub 2013 Mar 21.
Despite increasing incidences of human salmonellosis caused by consumption of contaminated vegetables, relatively little is known about how the plant immune system responds to and may inhibit Salmonella colonization. Here we show that Salmonella Typhimurium activates the plant immune system primarily due to its recognition of the flg22 region in Salmonella flagellin. Several previously identified plant genes that play a role in immunity were found to affect the host response to Salmonella. The Salmonella flg22 (Seflg22) peptide induced the immune response in leaves which effectively restricted the growth of Salmonella as well as the plant pathogenic bacterium, Pseudomonas syringae pv. tomato. Induction of immune responses by Seflg22 was dependent on the plant FLS2 receptor. Salmonella multiplied poorly on plant tissues similar to other bacteria which are non-pathogenic to plants. However, Salmonella populations increased significantly when co-inoculated with P. syringae pv. tomato but not when co-inoculated with a type III secretion system mutant of this pathogen. Our results suggest that Salmonella benefits from the immune-suppressing effects of plant pathogenic bacteria, and this growth enhancement may increase the risk of salmonellosis.
尽管因食用受污染蔬菜而导致的人类沙门氏菌病发病率不断上升，但人们对植物免疫系统如何对沙门氏菌定植做出反应以及可能抑制其定植的机制仍知之甚少。本研究表明，沙门氏菌 Typhimurium 主要通过其 Flagellin 中的 flg22 区域被识别而激活植物免疫系统。鉴定出几种参与免疫反应的植物基因，它们会影响宿主对沙门氏菌的反应。鉴定出的沙门氏菌 flg22 （Seflg22）肽在叶片中诱导免疫反应，有效地限制了沙门氏菌和植物病原菌丁香假单胞菌 pv. tomato 的生长。Seflg22 诱导免疫反应依赖于植物 FLS2 受体。沙门氏菌在类似于对植物无致病性的其他细菌的植物组织中繁殖不良。然而，当与丁香假单胞菌 pv. tomato 共同接种时，沙门氏菌的数量显著增加，但当与该病原体的 III 型分泌系统突变体共同接种时，沙门氏菌的数量并未增加。我们的研究结果表明，沙门氏菌受益于植物病原菌的免疫抑制作用，这种生长增强可能会增加沙门氏菌病的风险。
