Mitogen-activated protein kinases play an essential role in oxidative burst-independent expression of pathogenesis-related genes in parsley.
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.
Kroj
Thomas
T
Department of Stress and Developmental Biology, Institute of Plant Biochemistry, Weinberg 3, D-06120 Halle (Saale), Germany.
Rudd
Jason J
JJ
Nürnberger
Thorsten
T
Gäbler
Yvonne
Y
Lee
Justin
J
Scheel
Dierk
D
D000222:Adaptation, Physiological / Q000502:physiology*; D000595:Amino Acid Sequence; D015153:Blotting, Western; D002460:Cell Line; D018076:DNA, Complementary / Q000378:metabolism; D004789:Enzyme Activation; D018506:Gene Expression Regulation, Plant; D020935:MAP Kinase Signaling System; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D028528:Petroselinum / Q000201:enzymology / Q000382:microbiology*; D010838:Phytophthora / Q000378:metabolism; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011523:Protoplasts / Q000378:metabolism; D016897:Respiratory Burst; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D014162:Transfection
D018076:DNA, Complementary; D010940:Plant Proteins