Mitogen-activated Protein Kinases Play an Essential Role in Oxidative Burst-independent Expression of Pathogenesis-related Genes in Parsley

• Published in: The Journal of biological chemistry 2003-01, Vol.278 (4), p.2256-2264
• Main Authors: Kroj, Thomas, Rudd, Jason J, Nürnberger, Thorsten, Gäbler, Yvonne, Lee, Justin, Scheel, Dierk
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological - physiology; Amino Acid Sequence; Biochemistry; Biochemistry, Molecular Biology; Blotting, Western; Cell Line; DNA, Complementary - metabolism; Enzyme Activation; Gene Expression Regulation, Plant; Life Sciences; MAP Kinase Signaling System; Molecular Sequence Data; Mutagenesis, Site-Directed; Petroselinum - enzymology; Petroselinum - microbiology; Phytophthora - metabolism; Plant Physiological Phenomena; Plant Proteins - metabolism; Precipitin Tests; Promoter Regions, Genetic; Protoplasts - metabolism; Respiratory Burst; Reverse Transcriptase Polymerase Chain Reaction; Sequence Homology, Amino Acid; Time Factors; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M208200200

Plants are continuously exposed to attack by potential phytopathogens. Disease prevention requires pathogen recognition and the induction of a multifaceted defense response. We are studying the non-host disease resistance response of parsley to the oomycete, Phytophthora sojae using a cell culture-based system. Receptor-mediated recognition of P. sojae may be achieved through a thirteen amino acid peptide sequence (Pep-13) present within an abundant cell wall transglutaminase. Following recognition of this elicitor molecule, parsley cells mount a defense response, which includes the generation of reactive oxygen species (ROS) and transcriptional activation of genes encoding pathogenesis-related (PR) proteins or enzymes involved in the synthesis of antimicrobial phytoalexins. Treatment of parsley cells with the NADPH oxidase inhibitor, diphenylene iodonium (DPI), blocked both Pep-13-induced phytoalexin production and the accumulation of transcripts encoding enzymes involved in their synthesis. In contrast, DPI treatment had no effect upon Pep-13-induced PR gene expression, suggesting the existence of an oxidative burst-independent mechanism for the transcriptional activation of PR genes. The use of specific antibodies enabled the identification of three parsley mitogen-activated protein kinases (MAPKs) that are activated within the signal transduction pathway(s) triggered following recognition of Pep-13. Other environmental challenges failed to activate these kinases in parsley cells, suggesting that their activation plays a key role in defense signal transduction. Moreover, by making use of a protoplast co-transfection system overexpressing wild-type and loss-of-function MAPK mutants, we show an essential role for post-translational phosphorylation and activation of MAPKs for oxidative burst-independent PR promoter activation.