AtCPK1 calcium-dependent protein kinase mediates pathogen resistance in Arabidopsis

In mammals, lipid bodies play a key role during pathological and infectious diseases. However, our knowledge on the function of plant lipid bodies, apart from their role as the major site of lipid storage in seed tissues, remains limited. Here, we provide evidence that a calcium-dependent protein kinase (CPK) mediates pathogen resistance in Arabidopsis. AtCPK1 expression is rapidly induced by fungal elicitors. Loss-of-function mutants of AtCPK1 exhibit higher susceptibility to pathogen infection compared to wild-type plants. Conversely, over-expression of AtCPK1 leads to accumulation of salicylic acid (SA) and constitutive expression of SA-regulated defence and disease resistance genes, which, in turn, results in broad-spectrum protection against pathogen infection. Expression studies in mutants affected in SA-mediated defence responses revealed an interlocked feedback loop governing AtCPK1 expression and components of the SA-dependent signalling pathway. Moreover, we demonstrate the dual localization of AtCPK1 in lipid bodies and peroxisomes. Overall, our findings identify AtCPK1 as a component of the innate immune system of Arabidopsis plants. © 2010 Blackwell Publishing Ltd.M.C. was the recipient of a Ramón y Cajal contract from the Ministerio de Ciencia e Innovación (Spain). This work was supported by the Spanish Ministerio de Ciencia e Innovación (grants BIO2006-05583 and BIO2009-08719), with additional support from the CONSOLIDER Program on Agrigenomics and from the Department d’Innovació, Universitats i Empresa from the Generalitat de Catalunya (Xarsa de Referencia en Biotecnología and SGRO9626).Peer Reviewe