Endocytic Mechanisms in Plant Immunity

Plant immunity relies critically on the dynamic trafficking of plasma-membrane pattern recognition receptors (PRRs) that detect conserved microbial signatures. Upon ligand binding, receptors such as FLAGELLIN-SENSITIVE2 (FLS2) undergo ligand-induced internalisation via clathrin-mediated endocytosis, leading to either recycling to the cell surface or delivery to multivesicular bodies and the vacuole for degradation. This regulated endocytosis serves both to terminate or sustain signalling and to modulate receptor abundance in distinct nanodomains enriched in specific lipids and scaffolding proteins. Key endosomal sorting complexes recognise ubiquitin or SUMO modifications on activated receptors, determining their routing and the downstream immune responses. Vesicular trafficking components, including ARF-GEF proteins and ESCRT machinery, orchestrate the formation, motility and fusion of endocytic vesicles. Together, these steps fine-tune the amplitude and duration of pattern-triggered immune signalling, underpinning resistance to a broad spectrum of pathogens while preventing deleterious over-activation of defence pathways.

Research from Nature Portfolio

Recent studies have uncovered that conjugation of the SMALL UBIQUITIN-LIKE MODIFIER (SUMO) to FLS2 enhances the dissociation of the cytoplasmic kinase BIK1, triggering intracellular immune signalling. The induction of flagellin perception promotes SUMOylation of FLS2 at the plasma membrane, which in turn requires the targeted degradation of a deSUMOylating enzyme. Disruption of this modification abolishes pathogen-induced responses and compromises bacterial resistance, revealing a critical role for SUMO cycling in receptor endosomal sorting and signal propagation.

Endocytic Mechanisms in Plant Immunity publication trend

The graph below shows the total number of articles in endocytic mechanisms in plant immunity across all publications each year (not limited to Nature Index journals).

Technical terms

Pattern recognition receptor (PRR): A cell-surface protein that recognises conserved microbial molecules and initiates immune signalling.

Clathrin-mediated endocytosis (CME): A process in which clathrin coats assemble on the plasma membrane to form vesicles that internalise receptors and ligands.

SUMOylation: The covalent attachment of a SUMO protein to a target, modulating its activity, localisation or turnover.

Multivesicular body (MVB): An endosomal compartment containing internal vesicles that deliver cargo to the vacuole for degradation.

ARF-GEF: A guanine-nucleotide exchange factor for ADP-ribosylation factor GTPases, regulating vesicle budding from donor membranes.

Nanodomain: A specialised lipid- and protein-enriched microregion of the plasma membrane that organises signalling complexes.

References

1. Single-molecule analysis reveals the phosphorylation of FLS2 governs its spatiotemporal dynamics and immunity. eLife (2024).
2. SUMO conjugation to the pattern recognition receptor FLS2 triggers intracellular signalling in plant innate immunity. Nature Communications (2018).
3. Plant immune and growth receptors share common signalling components but localise to distinct plasma membrane nanodomains. eLife (2017).
4. Sensitivity to Flg22 Is Modulated by Ligand-Induced Degradation and de Novo Synthesis of the Endogenous Flagellin-Receptor FLAGELLIN-SENSING2. Plant Physiology (2013).
5. ESCRT-I Mediates FLS2 Endosomal Sorting and Plant Immunity. PLOS Genetics (2013).
6. The vesicular trafficking system component MIN7 is required for minimizing Fusarium graminearum infection. Journal of Experimental Botany (2021).
7. The bacterial quorum sensing signal DSF hijacks Arabidopsis thaliana sterol biosynthesis to suppress plant innate immunity. Life Science Alliance (2020).