title: Differential innate immune signalling via Ca(2+) sensor protein kinases.
abstract: Innate immunity represents the first line of inducible defence against microbial infection in plants and animals. In both kingdoms, recognition of pathogen- or microbe-associated molecular patterns (PAMPs or MAMPs, respectively), such as flagellin, initiates convergent signalling pathways involving mitogen-activated protein kinase (MAPK) cascades and global transcriptional changes to boost immunity. Although Ca(2+) has long been recognized as an essential and conserved primary mediator in plant defence responses, how Ca(2+) signals are sensed and relayed into early MAMP signalling is unknown. Using a functional genomic screen and genome-wide gene expression profiling, here we show that four calcium-dependent protein kinases (CDPKs) are Ca(2+)-sensor protein kinases critical for transcriptional reprogramming in plant innate immune signalling. Unexpectedly, CDPKs and MAPK cascades act differentially in four MAMP-mediated regulatory programs to control early genes involved in the synthesis of defence peptides and metabolites, cell wall modifications and redox signalling. Transcriptome profile comparison suggests that CDPKs are the convergence point of signalling triggered by most MAMPs. Double, triple and quadruple cpk mutant plants display progressively diminished oxidative burst and gene activation induced by the 22-amino-acid peptide flg22, as well as compromised pathogen defence. In contrast to negative roles of calmodulin and a calmodulin-activated transcription factor in plant defence, the present study reveals Ca(2+) signalling complexity and demonstrates key positive roles of specific CDPKs in initial MAMP signalling.
authors.affiliation: Department of Genetics, Harvard Medical School, Center for Computational and Integrative Biology, Massachusetts General Hospital, Massachusetts 02114, USA.
authors.forename: Marie
authors.initials: M
authors.lastname: Boudsocq
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Willmann
authors.forename: Matthew
authors.initials: M
authors.lastname: McCormack
authors.forename: Horim
authors.initials: H
authors.lastname: Lee
authors.forename: Libo
authors.initials: L
authors.lastname: Shan
authors.forename: Ping
authors.initials: P
authors.lastname: He
authors.forename: Jenifer
authors.initials: J
authors.lastname: Bush
authors.forename: Shu-Hua
authors.initials: SH
authors.lastname: Cheng
authors.forename: Jen
authors.initials: J
authors.lastname: Sheen
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000276:immunology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D005408:Flagellin / Q000737:chemistry / Q000276:immunology; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D018745:Genome, Plant / Q000235:genetics; D007113:Immunity, Innate / Q000276:immunology*; D020935:MAP Kinase Signaling System; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology; D011494:Protein Kinases / Q000378:metabolism*; D016897:Respiratory Burst; D014158:Transcription, Genetic; D017871:Calcium-Calmodulin-Dependent Protein Kinases
chemical_list: D029681:Arabidopsis Proteins; D002118:Calcium; D005408:Flagellin; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C508909:CPK11 protein, Arabidopsis