title: Phosphorylation of a WRKY transcription factor by two pathogen-responsive MAPKs drives phytoalexin biosynthesis in Arabidopsis.
abstract: Plant sensing of invading pathogens triggers massive metabolic reprogramming, including the induction of secondary antimicrobial compounds known as phytoalexins. We recently reported that MPK3 and MPK6, two pathogen-responsive mitogen-activated protein kinases, play essential roles in the induction of camalexin, the major phytoalexin in Arabidopsis thaliana. In search of the transcription factors downstream of MPK3/MPK6, we found that WRKY33 is required for MPK3/MPK6-induced camalexin biosynthesis. In wrky33 mutants, both gain-of-function MPK3/MPK6- and pathogen-induced camalexin production are compromised, which is associated with the loss of camalexin biosynthetic gene activation. WRKY33 is a pathogen-inducible transcription factor, whose expression is regulated by the MPK3/MPK6 cascade. Chromatin immunoprecipitation assays reveal that WRKY33 binds to its own promoter in vivo, suggesting a potential positive feedback regulatory loop. Furthermore, WRKY33 is a substrate of MPK3/MPK6. Mutation of MPK3/MPK6 phosphorylation sites in WRKY33 compromises its ability to complement the camalexin induction in the wrky33 mutant. Using a phospho-protein mobility shift assay, we demonstrate that WRKY33 is phosphorylated by MPK3/MPK6 in vivo in response to Botrytis cinerea infection. Based on these data, we conclude that WRKY33 functions downstream of MPK3/MPK6 in reprogramming the expression of camalexin biosynthetic genes, which drives the metabolic flow to camalexin production in Arabidopsis challenged by pathogens.
authors.affiliation: Department of Biochemistry, Interdisciplinary Plant Group, and Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211, USA.
authors.forename: Guohong
authors.initials: G
authors.lastname: Mao
authors.forename: Xiangzong
authors.initials: X
authors.lastname: Meng
authors.forename: Yidong
authors.initials: Y
authors.lastname: Liu
authors.forename: Zuyu
authors.initials: Z
authors.lastname: Zheng
authors.forename: Zhixiang
authors.initials: Z
authors.lastname: Chen
authors.forename: Shuqun
authors.initials: S
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020171:Botrytis / Q000502:physiology*; D018744:DNA, Plant / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D007211:Indoles / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D010766:Phosphorylation; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D036226:Seedlings / Q000378:metabolism; D012717:Sesquiterpenes / Q000378:metabolism*; D013844:Thiazoles / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D000094162:Phytoalexins
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; D007211:Indoles; D012717:Sesquiterpenes; D013844:Thiazoles; D014157:Transcription Factors; C517860:WRKY33 protein, Arabidopsis; C102405:camalexin; C458516:AtMPK3 protein, Arabidopsis; C436293:MPK6 protein, Arabidopsis; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D000094162:Phytoalexins