Bacterial outer membrane vesicles (OMVs) perform a variety of functions in bacterial survival and virulence. In mammalian systems, OMVs activate immune responses and are exploited as vaccines. However, little work has focused on the interactions of OMVs with plant hosts. Here, we report that OMVs from Pseudomonas syringae and P. fluorescens activate plant immune responses that protect against bacterial and oomycete pathogens. OMV-mediated immunomodulatory activity from these species displayed different sensitivity to biochemical stressors, reflecting differences in OMV content. Importantly, OMV-mediated plant responses are distinct from those triggered by conserved bacterial epitopes or effector molecules alone. Our study shows that OMV-induced protective immune responses are independent of the T3SS and protein, but that OMV-mediated seedling growth inhibition largely depends on proteinaceous components. OMVs provide a unique opportunity to understand the interplay between virulence and host response strategies and add a new dimension to consider in host-microbe interactions.

细菌外膜囊泡 (OMV) 在细菌存活和毒力方面发挥着多种功能。在哺乳动物系统中，OMV 激活免疫反应并被用作疫苗。然而，很少有工作关注 OMV 与植物宿主的相互作用。在这里，我们报告了来自Pseudomonas syringae和P. fluorescens的 OMV激活植物免疫反应，防止细菌和卵菌病原体。这些物种的 OMV 介导的免疫调节活性对生化应激源表现出不同的敏感性，反映了 OMV 含量的差异。重要的是，OMV 介导的植物反应不同于仅由保守的细菌表位或效应分子触发的植物反应。我们的研究表明，OMV 诱导的保护性免疫反应不依赖于 T3SS 和蛋白质，但 OMV 介导的幼苗生长抑制在很大程度上取决于蛋白质成分。OMV 提供了一个独特的机会来了解毒力和宿主反应策略之间的相互作用，并增加了一个新的维度来考虑宿主-微生物的相互作用。