Ca2+/calmodulin regulates salicylic-acid-mediated plant immunity

• Published in: Nature (London) Vol. 457; no. 7233; pp. 1154 - 1158
• Main Authors: Du, Liqun, Ali, Gul S, Simons, Kayla A, Hou, Jingguo, Yang, Tianbao, Reddy, A.S.N, Poovaiah, B.W
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 26.02.2009; Nature Publishing Group
• Subjects: Arabidopsis thaliana; bacterial diseases of plants; Bacterial plant pathogens; Biological and medical sciences; calcium; calmodulin; disease resistance; ESD1 promoter; Fundamental and applied biological sciences. Psychology; gene expression regulation; Humanities and Social Sciences; letter; multidisciplinary; Pathology. Damages, economic importance; Phytopathology. Animal pests. Plant and forest protection; promoter regions; protein binding; Pseudomonas syringae pv. tomato; salicylic acid; Science; Science (multidisciplinary); signal transduction; transcription factors; Pseudomonadales; Plant pathology; Plant pathogen; Organism defense; Epistasis; Regulator; Immunity; Mediation; Arabidopsis thaliana; Signal transduction; Disease resistance; Regulation(control); Plant; Microorganism resistance; Calcium ion; Cruciferae; Pseudomonas syringae; Dicotyledones; Angiospermae; Bacteria; Pseudomonadaceae; Transcription factor; Calmodulin; Salicylic acid; Vegetals; Immune response; Pathophysiology; Biochemical compound; Inorganic ion; Host agent relation; Immune regulation; Gene expression; Sensitivity resistance; Defense mechanism; Spermatophyta; Mediator; Mutation; Molecular biology
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature07612

Intracellular calcium transients during plant-pathogen interactions are necessary early events leading to local and systemic acquired resistance. Salicylic acid, a critical messenger, is also required for both of these responses, but whether and how salicylic acid level is regulated by Ca2+ signalling during plant-pathogen interaction is unclear. Here we report a mechanism connecting Ca2+ signal to salicylic-acid-mediated immune response through calmodulin, AtSR1 (also known as CAMTA3), a Ca2+/calmodulin-binding transcription factor, and EDS1, an established regulator of salicylic acid level. Constitutive disease resistance and elevated levels of salicylic acid in loss-of-function alleles of Arabidopsis AtSR1 suggest that AtSR1 is a negative regulator of plant immunity. This was confirmed by epistasis analysis with mutants of compromised salicylic acid accumulation and disease resistance. We show that AtSR1 interacts with the promoter of EDS1 and represses its expression. Furthermore, Ca2+/calmodulin-binding to AtSR1 is required for suppression of plant defence, indicating a direct role for Ca2+/calmodulin in regulating the function of AtSR1. These results reveal a previously unknown regulatory mechanism linking Ca2+ signalling to salicylic acid level.