ESCRT: A Cellular Nexus of Plant Immunity and Pathogen Counter-Strategies.

Abstract

The endosomal sorting complex required for transport (ESCRT) machinery consists of multiprotein complexes conserved across all eukaryotic lineages that function in several fundamental cellular processes. Among these are sorting endocytosed membrane proteins, multivesicular body (MVB) biogenesis, and autophagy. Despite the fact that these processes are also critical for plant immune responses, relatively little work has been done studying ESCRT in the context of plant immunity. Several studies indicate that ESCRT influences PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI) by controlling the endosomal sorting of membrane-localized or associated immune signalling components, thereby affecting their localization and stability. Very few studies have examined ESCRT's role in MVB biogenesis during pathogen infection, but because ESCRT drives the formation of MVBs, it is likely involved in all the defence responses MVBs contribute to, such as extracellular vesicle (EV) release and cell wall reinforcement. Similarly, ESCRT's involvement in autophagy during pathogen infection is understudied, but because ESCRT is responsible for phagophore sealing, it is probably required for autophagy's roles in plant immunity, which include its complicated relationship with programmed cell death. ESCRT's relevance to plant immunity is also supported by instances of pathogen effectors targeting ESCRT complexes and evidence suggesting certain ESCRT subunits are monitored by the plant immune system. In this review, we highlight evidence supporting ESCRT's importance in plant immunity, discuss the mechanisms by which ESCRT contributes to immune responses, and identify the major knowledge gaps in this area.