Chitin receptor CERK1 links salt stress and chitin-triggered innate immunity in Arabidopsis
Catherine Espinoza, Yan Liang, Gary Stacey
In nature, plants need to respond to multiple environmental stresses that require involvement and fine-tuning of different stress signaling pathways. Cross-tolerance in which plants pre-treated with chitin (a fungal microbe-associated molecular pattern) have improved salt tolerance was observed in Arabidopsis but is not well understood. Here, we show a unique link between chitin and salt signaling mediated by the chitin receptor CHITIN ELICITOR RECEPTOR KINASE 1 (CERK1). Transcriptome analysis revealed that salt stress-induced genes are highly correlated with chitin-induced genes, while this was not observed with other microbe-associated molecular patterns (MAMP) or with other abiotic stresses. The cerk1 mutant was more susceptible to NaCl than wild type. cerk1 plants had an irregular increase of cytosolic calcium ([Ca2+]cyt) after NaCl treatment. Bimolecular fluorescence complementation (BiFC) and co-immuno precipitation experiments indicated that CERK1 physically interacts with ANNEXIN 1 (ANN1), which was reported to form a calcium-permeable channel that contributes to the NaCl-induced [Ca2+]cyt signal. In turn, ann1 mutants showed elevated chitin-induced rapid responses. In short, molecular components previously shown to function in chitin or salt signaling physically interact and intimately link the downstream responses to fungal attack and salt stress.