Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín (EEZ-CSIC), Granada, Spain.
Environ Microbiol Rep. 2013 Dec;5(6):841-50. doi: 10.1111/1758-2229.12086. Epub 2013 Aug 6.
Flavonoids are among the most abundant plant secondary metabolites involved in plant protection against pathogens, but micro-organisms have developed resistance mechanisms to those compounds. We previously demonstrated that the MexAB-OprM efflux pump mediates resistance of Pseudomonas syringae pv. tomato (Pto) DC3000 to flavonoids, facilitating its survival and the colonization of the host. Here, we have shown that tomato plants respond to Pto infection producing flavonoids and other phenolic compounds. The effects of flavonoids on key traits of this model plant-pathogen bacterium have also been investigated observing that they reduce Pto swimming and swarming because of the loss of flagella, and also inhibited the expression and assembly of a functional type III secretion system. Those effects were more severe in a mutant lacking the MexAB-OprM pump. Our results suggest that flavonoids inhibit the function of the GacS/GacA two-component system, causing a depletion of rsmY RNA, therefore affecting the synthesis of two important virulence factors in Pto DC3000, flagella and the type III secretion system. These data provide new insights into the flavonoid role in the molecular dialog between host and pathogen.
类黄酮是植物中含量最丰富的次生代谢产物之一，参与植物抵御病原体的保护，但微生物已经发展出了对这些化合物的抗性机制。我们之前证明，MexAB-OprM 外排泵介导了丁香假单胞菌 pv.番茄（Pto）DC3000 对类黄酮的抗性，促进了其在宿主中的生存和定植。在这里，我们已经表明，番茄植物对 Pto 感染会产生类黄酮和其他酚类化合物。我们还研究了类黄酮对这种模式植物-病原菌细菌关键特性的影响，发现它们由于鞭毛的丧失而降低了 Pto 的游动和群集，并且还抑制了功能性 III 型分泌系统的表达和组装。在缺乏 MexAB-OprM 泵的突变体中，这些影响更为严重。我们的结果表明，类黄酮抑制了 GacS/GacA 双组分系统的功能，导致 rsmY RNA 的耗竭，从而影响了 Pto DC3000 中两种重要毒力因子的合成，鞭毛和 III 型分泌系统。这些数据为类黄酮在宿主和病原体之间的分子对话中的作用提供了新的见解。
