title: Function of a mitogen-activated protein kinase pathway in N gene-mediated resistance in tobacco.
abstract: The active defense of plants against pathogens often includes rapid and localized cell death known as hypersensitive response (HR). Protein phosphorylation and dephosphorylation are implicated in this event based on studies using protein kinase and phosphatase inhibitors. Recent transient gain-of-function studies demonstrated that the activation of salicylic acid-induced protein kinase (SIPK) and wounding-induced protein kinase (WIPK), two tobacco mitogen-activated protein kinases (MAPKs) by their upstream MAPK kinase (MAPKK), NtMEK2 leads to HR-like cell death. Here, we report that the conserved kinase interaction motif (KIM) in MAPKKs is required for NtMEK2 function. Mutation of the conserved basic amino acids in this motif, or the deletion of N-terminal 64 amino acids containing this motif significantly compromised or abolished the ability of NtMEK2DD to activate SIPK/WIPK in vivo. These mutants were also defective in interacting with SIPK and WIPK, suggesting protein-protein interaction is required for the functional integrity of this MAPK cascade. To eliminate Agrobacterium that is known to activate a number of defense responses in transient transformation experiments, we generated permanent transgenic plants. Induction of NtMEK2DD expression by dexamethasone induced HR-like cell death in both T1 and T2 plants. In addition, by using PVX-induced gene silencing, we demonstrated that the suppression of all three known components in the NtMEK2-SIPK/WIPK pathway attenuated N gene-mediated TMV resistance. Together with previous report that SIPK and WIPK are activated by TMV in a gene-for-gene-dependent manner, we conclude that NtMEK2-SIPK/WIPK pathway plays a positive role in N gene-mediated resistance, possibly through regulating HR cell death.
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley & Plant Gene Expression Center, USDA-ARS, 800 Buchanan St., Albany, CA 94710, USA.
authors.forename: Hailing
authors.initials: H
authors.lastname: Jin
authors.forename: Yidong
authors.initials: Y
authors.lastname: Liu
authors.forename: Kwang-Yeol
authors.initials: KY
authors.lastname: Yang
authors.forename: Cha Young
authors.initials: CY
authors.lastname: Kim
authors.forename: Barbara
authors.initials: B
authors.lastname: Baker
authors.forename: Shuqun
authors.initials: S
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D005816:Genetic Complementation Test; D007113:Immunity, Innate / Q000235:genetics; D048370:MAP Kinase Kinase 2; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics* / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D019590:Nucleocapsid Proteins / Q000235:genetics* / Q000378:metabolism; D010935:Plant Diseases / Q000235:genetics / Q000821:virology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D017863:Potexvirus / Q000254:growth & development; D025941:Protein Interaction Mapping; D011505:Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D014026:Nicotiana / Q000201:enzymology / Q000235:genetics* / Q000821:virology; D014027:Tobacco Mosaic Virus / Q000254:growth & development
chemical_list: D019590:Nucleocapsid Proteins; D010940:Plant Proteins; D011505:Protein-Tyrosine Kinases; D020928:Mitogen-Activated Protein Kinases; C106405:SA-induced protein kinase; C113423:WIPK protein, Nicotiana tabacum; D048370:MAP Kinase Kinase 2; D020929:Mitogen-Activated Protein Kinase Kinases