LYM2-dependent chitin perception limits molecular flux via plasmodesmata

Abstract

Chitin acts as a pathogen-associated molecular pattern from fungal pathogens whose perception triggers a range of defense responses. We show that LYSIN MOTIF DOMAIN-CONTAINING GLY-COSYLPHOSPHATIDYLINOSITOL-ANCHORED PROTEIN 2 (LYM2), the Arabidopsis homolog of a rice chitin receptor-like protein, mediates a reduction in molecular flux via plasmodesmata in the presence of chitin. For this response, lym2-1 mutants are insensitive to the presence of chitin, but not to the flagellin derivative flg22. Surprisingly, the chitin-recognition receptor CHITIN ELCITOR RE-CEPTOR KINASE 1 (CERK1) is not required for chitin-induced changes to plasmodesmata flux, suggesting that there are at least two chitin-activated response pathways in Arabidopsis and that LYM2 is not required for CERK1-mediated chitin-triggered defense responses, indicating that these pathways are independent. In accordance with a role in the regulation of intercellular flux, LYM2 is resident at the plasma membrane and is enriched at plasmodesmata. Chitin-triggered regulation of molecular flux between cells is required for defense responses against the fungal pathogen Botrytis cinerea, and thus we conclude that the regulation of symplastic continuity and molecular flux between cells is a vital component of chitin-triggered immunity in Arabidopsis.PAMP-triggered immunity | cell-to-cell communication

Salicylic Acid Regulates Arabidopsis Microbial Pattern Receptor Kinase Levels and Signaling

“…Additionally, Wang et al (2013) reported that SA increases the intensity of callose staining and the concomitant partial restriction of plasmodesmata openings. In another study, FLS2-green fluorescent protein was seen to partially colocalize with sites of basal callose deposition that appear to be in positions of plasmodesmata (punctate structures along the plasma membrane; Faulkner et al, 2013). It seems possible that PRRs (FLS2, BAK1, and CERK1) together with ACD6 form a signaling platform(s) that is needed for the callose response to SA/BTH.…”

Chitin-induced activation of immune signaling by the rice receptor CEBiP relies on a unique sandwich-type dimerization

“…Interestingly, it was recently reported that LYM2 contributes to disease resistance of Arabidopsis independent of chitin signaling by CERK1 (39,40). Faulkner indicated that the plasmodesmatalocalized LYM2 is involved in chitin-induced plasmodesmata closure, which seems to be important for chitin-triggerd immunity (39). Thus, the ligand-induced dimerization of CERK1 directly links to the downstream signaling in Arabidopsis.…”

“…CEBiP homolog in Arabidopsis, LYM2 (AtCEBiP), seems not to contribute to chitin signaling, although the protein binds chitin oligosaccharides with a high affinity (9,12). Interestingly, it was recently reported that LYM2 contributes to disease resistance of Arabidopsis independent of chitin signaling by CERK1 (39,40). Faulkner indicated that the plasmodesmatalocalized LYM2 is involved in chitin-induced plasmodesmata closure, which seems to be important for chitin-triggerd immunity (39).…”

The C2-domain protein QUIRKY and the receptor-like kinase STRUBBELIG localize to plasmodesmata and mediate tissue morphogenesis in Arabidopsis thaliana

“…A number of functionally characterized RLKs have been reported to be present at PD, including CRINKLY 4 (CR4) (Tian et al, 2007), ARABIDOPSIS CRINKLY 4 (ACR4) and CLAVATA 1 (CLV1) (Stahl et al, 2013), FLAGELLIN-SENSITIVE 2 (FLS2) (Faulkner et al, 2013) however, how RLKs are targeted to PD. To obtain insights into the mechanism, we sought to identify domains of SUB that are involved in this process.…”