In Planta Processing and Glycosylation of a Nematode CLAVATA3/ENDOSPERM SURROUNDING REGION-Like Effector and Its Interaction with a Host CLAVATA2-Like Receptor to Promote Parasitism

Abstract

Like other biotrophic plant pathogens, plant-parasitic nematodes secrete effector proteins into host cells to facilitate infection. Effector proteins that mimic plant CLAVATA3/ENDOSPERM SURROUNDING REGION-related (CLE) proteins have been identified in several cyst nematodes, including the potato cyst nematode (PCN); however, the mechanistic details of this crosskingdom mimicry are poorly understood. Plant CLEs are posttranslationally modified and proteolytically processed to function as bioactive ligands critical to various aspects of plant development. Using ectopic expression coupled with nanoliquid chromatography-tandem mass spectrometry analysis, we show that the in planta mature form of proGrCLE1, a multidomain CLE effector secreted by PCN during infection, is a 12-amino acid arabinosylated glycopeptide (named GrCLE1-1Hyp4,7g) with striking structural similarity to mature plant CLE peptides. This glycopeptide is more resistant to hydrolytic degradation and binds with higher affinity to a CLAVATA2-like receptor (StCLV2) from potato (Solanum tuberosum) than its nonglycosylated forms. We further show that StCLV2 is highly up-regulated at nematode infection sites and that transgenic potatoes with reduced StCLV2 expression are less susceptible to PCN infection, indicating that interference of the CLV2-mediated signaling pathway confers nematode resistance in crop plants. These results strongly suggest that phytonematodes have evolved to utilize host cellular posttranslational modification and processing machinery for the activation of CLE effectors following secretion into plant cells and highlight the significance of arabinosylation in regulating nematode CLE effector activity. Our finding also provides evidence that multidomain CLEs are modified and processed similarly to single-domain CLEs, adding new insight into CLE maturation in plants.

Cellular Signaling Pathways and Posttranslational Modifications Mediated by Nematode Effector Proteins

“…The ability of cyst nematode CLElike effectors to complement the Arabidopsis clv3-2 null mutant provided the first clue that these effectors should undergo PTMs and proteolytic processing, similar to that of plant CLE precursors, to become bioactive CLE peptides (Shinohara and Matsubayashi, 2010;Shinohara et al, 2012;Okamoto et al, 2013). Consistent with this hypothesis, a recent study demonstrated that a multidomain CLE effector from G. rostochiensis (GrCLE1) was glycosylated and processed into 12-amino acid arabinosylated glycopeptides (GrCLE1-1Hyp4,7g), similar in structure to bioactive plant CLE peptides (Chen et al, 2015b). It was further demonstrated that this glycosylated peptide is more resistant to hydrolytic degradation and binds with much higher affinity to the potato CLV2-like receptor (StCLV2) than its nonglycosylated forms (Fig.…”

A microbially derived tyrosine‐sulfated peptide mimics a plant peptide hormone

“…In some cases, the ability of a pathogen to mimic a host biological process can facilitate pathogen infection (Weiler et al ., ; Melotto et al ., ; Mitchum et al ., ; Chen et al ., ). We therefore tested whether RaxX contributes to the virulence of Xoo in plants lacking XA21.…”

Plant-Pathogen Effectors: Cellular Probes Interfering with Plant Defenses in Spatial and Temporal Manners

“…In plants, CLE perception is critical for cell-to-cell communication and controls multiple developmental processes (61). CLE-like effectors are posttranslationally processed, revealing a 12–13 amino acid mature peptide ligand with similarity to plant CLE peptides (16). Overexpression of CLE-like effectors in Arabidopsis results in premature meristem termination and phenocopies plants overexpressing CLE peptides (145).…”