Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China.
Plant Commun. 2020 Jun 12;1(4):100085. doi: 10.1016/j.xplc.2020.100085. eCollection 2020 Jul 13.
Plants associate with diverse microbes that exert beneficial, neutral, or pathogenic effects inside the host. During the initial stages of invasion, the plant apoplast constitutes a hospitable environment for invading microbes, providing both water and nutrients. In response to microbial infection, a number of secreted proteins from host cells accumulate in the apoplastic space, which is related to microbial association or colonization processes. However, the molecular mechanisms underlying plant modulation of the apoplast environment and how plant-secreted proteases are involved in pathogen resistance are still poorly understood. Recently, several studies have reported the roles of apoplastic proteases in plant resistance against bacteria, fungi, and oomycetes. On the other hand, microbe-secreted proteins directly and/or indirectly inhibit host-derived apoplastic proteases to promote infection. These findings illustrate the importance of apoplastic proteases in plant-microbe interactions. Therefore, understanding the protease-mediated apoplastic battle between hosts and pathogens is of fundamental importance for understanding plant-pathogen interactions. Here, we provide an overview of plant-microbe interactions in the apoplastic space. We define the apoplast, summarize the physical and chemical properties of these structures, and discuss the roles of plant apoplastic proteases and pathogen protease inhibitors in host-microbe interactions. Challenges and future perspectives for research into protease-mediated apoplastic interactions are discussed, which may facilitate the engineering of resistant crops.
植物与多种微生物共生，这些微生物在宿主内部产生有益、中性或致病的影响。在入侵的初始阶段，植物质外体为入侵微生物提供了一个适宜的环境，提供水和养分。植物细胞分泌的许多蛋白质在质外体空间中积累，这与微生物的共生或定殖过程有关。然而，植物调节质外体环境的分子机制以及植物分泌的蛋白酶如何参与病原体抗性仍然知之甚少。最近，有几项研究报道了质外体蛋白酶在植物抵抗细菌、真菌和卵菌中的作用。另一方面，微生物分泌的蛋白质直接和/或间接抑制宿主来源的质外体蛋白酶，以促进感染。这些发现说明了质外体蛋白酶在植物-微生物相互作用中的重要性。因此，了解宿主和病原体之间质外体蛋白酶介导的斗争对于理解植物-病原体相互作用至关重要。在这里，我们概述了质外体空间中植物-微生物的相互作用。我们定义了质外体，总结了这些结构的物理和化学性质，并讨论了植物质外体蛋白酶和病原体蛋白酶抑制剂在宿主-微生物相互作用中的作用。还讨论了研究质外体蛋白酶介导的相互作用所面临的挑战和未来展望，这可能有助于培育抗性作物。
