Castiblanco Luisa F, Triplett Lindsay R, Sundin George W
Department of Plant, Soil and Microbial Sciences, Center for Microbial Pathogenesis, Michigan State University, East Lansing, MI, United States.
Department of Plant Pathology and Ecology, The Connecticut Agricultural Experiment Station, New Haven, CT, United States.
Front Microbiol. 2018 Feb 8;9:146. doi: 10.3389/fmicb.2018.00146. eCollection 2018.
Type III secretion (TTS) chaperones are critical for the delivery of many effector proteins from Gram-negative bacterial pathogens into host cells, functioning in the stabilization and hierarchical delivery of the effectors to the type III secretion system (TTSS). The plant pathogen secretes at least four TTS effector proteins: DspE, Eop1, Eop3, and Eop4. DspE specifically interacts with the TTS chaperone protein DspF, which stabilizes the effector protein in the cytoplasm and promotes its efficient translocation through the TTSS. However, the role of chaperones in regulating the delivery of other secreted effectors is unknown. In this study, we identified functional interactions between the effector proteins DspE, Eop1, and Eop3 with the TTS chaperones DspF, Esc1 and Esc3 in yeast. Using site-directed mutagenesis, secretion, and translocation assays, we demonstrated that the three TTS chaperones have additive roles for the secretion and translocation of DspE into plant cells whereas DspF negatively affects the translocation of Eop1 and Eop3. Collectively, these results indicate that TTS chaperone proteins exhibit a cooperative behavior to orchestrate the effector secretion and translocation dynamics in .
III型分泌（TTS）分子伴侣对于革兰氏阴性细菌病原体的许多效应蛋白进入宿主细胞至关重要，其作用是稳定效应蛋白并将其分级递送至III型分泌系统（TTSS）。植物病原体 分泌至少四种TTS效应蛋白：DspE、Eop1、Eop3和Eop4。DspE与TTS分子伴侣蛋白DspF特异性相互作用，DspF可在细胞质中稳定效应蛋白并促进其通过TTSS有效转运。然而，分子伴侣在调节其他分泌效应蛋白递送中的作用尚不清楚。在本研究中，我们在酵母中鉴定了效应蛋白DspE、Eop1和Eop3与TTS分子伴侣DspF、Esc1和Esc3之间的功能相互作用。通过定点诱变、分泌和转运分析，我们证明这三种TTS分子伴侣对DspE分泌到植物细胞以及转运具有累加作用，而DspF对Eop1和Eop3的转运具有负面影响。总体而言，这些结果表明TTS分子伴侣蛋白表现出协同行为，以协调 中的效应蛋白分泌和转移动力学。
