A Moving View: Subcellular Trafficking Processes in Pattern Recognition Receptor–Triggered Plant Immunity

Abstract

A significant challenge for plants is to induce localized defense responses at sites of pathogen attack. Therefore, host subcellular trafficking processes enable accumulation and exchange of defense compounds, which contributes to the plant on-site defenses in response to pathogen perception. This review summarizes our current understanding of the transport processes that facilitate immunity, the significance of which is highlighted by pathogens reprogramming membrane trafficking through host cell translocated effectors. Prominent immune-related cargos of plant trafficking pathways are the pattern recognition receptors (PRRs), which must be present at the plasma membrane to sense microbes in the apoplast. We focus on the dynamic localization of the FLS2 receptor and discuss the pathways that regulate receptor transport within the cell and their link to FLS2-mediated immunity. One emerging theme is that ligand-induced late endocytic trafficking is conserved across different PRR protein families as well as across different plant species.

Allelic diversity in an NLR geneBPH9enables rice to combat planthopper variation

“…ES has recently attracted much attention in regulating immune receptor activation, signal transduction, and execution of multiple defense responses, including pathogen-induced programmed cell death, cell wall synthesis, and callose deposition (43,44). Because of its pivotal role for plants, some pathogens cleverly target their effectors to ES to interfere with secretory and endocytic trafficking to promote successful infection (45).…”

“…It can be inferred that BPH1/9-9 and its alleles may act as a supervisor residing in the ES to recognize the feeding of BPH. Once perceiving the signals of BPH, the secretory-trafficking system can deliver enzymes to deposit callose, thicken cell wall, or produce defense compounds (43). Because plant resistance response is a series of complicated and multilayered orchestration of defense strategies, wide distribution of resistance proteins in the ES would contribute to the rapid activation of these downstream responses.…”

An Aphid Effector Targets Trafficking Protein VPS52 in a Host-Specific Manner to Promote Virulence

“…The negative impact of VPS52 on aphid virulence suggests this host protein either contributes to plant immunity to aphids, or perhaps negatively regulates nutrient availability in the phloem. In recent years, it has become evident that host vesicle trafficking regulates plant defense responses to pathogenic microbes (Teh and Hofius, 2014;Ben Khaled et al, 2015). For example, receptor activation, and activation of defense signaling, as well as redirecting cargo to infection sites, all require host trafficking machinery.…”

Receptor Kinases in Plant-Pathogen Interactions: More Than Pattern Recognition

“…Protein accumulation of PRRs is also affected by endocytosis (Ben Khaled et al, 2015;Frescatada-Rosa et al, 2015;Couto and Zipfel, 2016). flg22 induces FLS2 internalization and degradation in Arabidopsis (Robatzek et al, 2006).…”

“…Similarly, Cf-4-and Cf-9-mediated resistance and endocytosis in tomato plants require ligand-induced recruitment of BAK1, indicating that diverse classes of PRRs share similar requirements for initiation of resistance and endocytosis (Postma et al, 2016). Readers are referred to recent reviews for detailed discussion on the endocytic regulation of plant RKs and RPs (Ben Khaled et al, 2015;Frescatada-Rosa et al, 2015).…”