CaCDPK15 positively regulates pepper responses to Ralstonia solanacearum inoculation and forms a positive-feedback loop with CaWRKY40 to amplify defense signaling

• Published in: Scientific reports Vol. 6; no. 1; p. 22439
• Main Authors: Shen, Lei, Yang, Sheng, Yang, Tong, Liang, Jiaqi, Cheng, Wei, Wen, Jiayu, Liu, Yanyan, Li, Jiazhi, Shi, Lanping, Tang, Qian, Shi, Wei, Hu, Jiong, Liu, Cailing, Zhang, Yangwen, Mou, Shaoliang, Liu, Zhiqin, Cai, Hanyang, He, Li, Guan, Deyi, Wu, Yang, He, Shuilin
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.03.2016; Nature Publishing Group
• Subjects: 38/15; 38/35; 38/89; 631/449/2169; 631/80/82; Abiotic stress; Abscisic acid; Abscisic Acid - pharmacology; Acetates - pharmacology; Boxes; Capsicum - metabolism; Capsicum - microbiology; Cell death; Cell Death - genetics; Chromatin; Cyclopentanes - pharmacology; Disease Resistance - genetics; Disease Resistance - immunology; Feedback; Flowers & plants; Gene expression; Gene Expression Regulation, Plant - genetics; Gene Silencing; Genomes; Herbivores; High temperature; Humanities and Social Sciences; Humidity; Hydrogen Peroxide - metabolism; Hypersensitive response; Immunoprecipitation; Inoculation; Kinases; Life sciences; Localization; Methyl jasmonate; multidisciplinary; Organophosphorus Compounds - pharmacology; Oxylipins - pharmacology; Pathogens; Plant Diseases - microbiology; Plant Growth Regulators - pharmacology; Plant immunity; Plasma; Promoter Regions, Genetic - genetics; Promoters; Protein Binding; Protein Kinases - genetics; Protein Kinases - metabolism; Proteins; Ralstonia solanacearum - physiology; Roles; Salicylic acid; Salicylic Acid - pharmacology; Science; Science (multidisciplinary); Signal Transduction - genetics; Transcription Factors - genetics; Transcription Factors - metabolism; Vegetables
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep22439

CaWRKY40 is a positive regulator of pepper ( Capsicum annum ) response to Ralstonia solanacearum inoculation (RSI), but the underlying mechanism remains largely unknown. Here, we functionally characterize CaCDPK15 in the defense signaling mediated by CaWRKY40. Pathogen-responsive TGA, W, and ERE boxes were identified in the CaCDPK15 promoter (p CaCDPK15 ), and p CaCDPK15 -driven GUS expression was significantly enhanced in response to RSI and exogenously applied salicylic acid, methyl jasmonate, abscisic acid, and ethephon. Virus-induced gene silencing (VIGS) of CaCDPK15 significantly increased the susceptibility of pepper to RSI and downregulated the immunity-associated markers CaNPR1 , CaPR1 , and CaDEF1 . By contrast, transient CaCDPK15 overexpression significantly activated hypersensitive response associated cell death, upregulated the immunity-associated marker genes, upregulated CaWRKY40 expression, and enriched CaWRKY40 at the promoters of its targets genes. Although CaCDPK15 failed to interact with CaWRKY40, the direct binding of CaWRKY40 to p CaCDPK15 was detected by chromatin immunoprecipitation, which was significantly potentiated by RSI in pepper plants. These combined results suggest that RSI in pepper induces CaCDPK15 and indirectly activates downstream CaWRKY40 , which in turn potentiates CaCDPK15 expression. This positive-feedback loop would amplify defense signaling against RSI and efficiently activate strong plant immunity.