Plant pathogens perturb their hosts to create environments suitable for their proliferation, including the suppression of immunity and promotion of water and nutrient availability. Although necrotrophs obtain water and nutrients by disrupting host-cell integrity, it is unknown whether hemibiotrophs, such as the bacterial pathogen Pantoea stewartii subsp. stewartii (Pnss), actively liberate water and nutrients during the early, biotrophic phase of infection. Here, we show that water and metabolite accumulation in the apoplast of Pnss-infected maize leaves precedes the disruption of host-cell integrity. Nutrient acquisition during this biotrophic phase is a dynamic process; the partitioning of metabolites into the apoplast rate limiting for their assimilation by proliferating Pnss cells. The formation of a hydrated and nutritive apoplast is driven by an AvrE-family type III effector, WtsE. Given the broad distribution of AvrE-family effectors, this work highlights the importance of actively acquiring water and nutrients for the proliferation of phytopathogenic bacteria during biotrophy.

植物病原体扰乱它们的宿主以创造适合其增殖的环境，包括抑制免疫力和促进水和养分的可用性。尽管 necrotrophs 通过破坏宿主细胞的完整性来获取水和营养物质，但尚不清楚 hemibiotrophs，例如细菌病原体Pantoeastewartii subsp。Stewartii ( Pnss ) 在感染的早期生物营养阶段积极释放水分和营养。在这里，我们展示了Pnss质外体中的水和代谢物积累受感染的玉米叶先于宿主细胞完整性的破坏。在这个生物营养阶段的营养获取是一个动态的过程。代谢物分配到质外体速率限制了它们通过增殖的Pnss细胞的同化。水合和营养质外体的形成是由 AvrE 家族 III 型效应子 WtsE 驱动的。鉴于 AvrE 家族效应子的广泛分布，这项工作强调了在生物营养过程中积极获取水和养分对植物病原细菌增殖的重要性。