NPK1, an MEKK1-like mitogen-activated protein kinase kinase kinase, regulates innate immunity and development in plants

Dev Cell. 2002 Aug;3(2):291-7. doi: 10.1016/s1534-5807(02)00205-8.


Mitogen-activated protein kinase (MAPK) cascades are rapidly activated upon plant recognition of invading pathogens. Here, we describe the use of virus-induced gene silencing (VIGS) to study the role of candidate plant MAP kinase kinase kinase (MAPKKK) homologs of human MEKK1 in pathogen-resistance pathways. We demonstrate that silencing expression of a tobacco MAPKKK, Nicotiana Protein Kinase 1 (NPK1), interferes with the function of the disease-resistance genes N, Bs2, and Rx, but does not affect Pto- and Cf4-mediated resistance. Further, NPK1-silenced plants also exhibit reduced cell size, defective cytokinesis, and an overall dwarf phenotype. Our results provide evidence that NPK1 functions in the regulation of N-, Bs2-, and Rx-mediated resistance responses and may play a role in one or more MAPK cascades, regulating multiple cellular processes.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Cell Size / genetics
  • Gene Expression Regulation, Plant / physiology*
  • Gene Silencing / physiology*
  • Genetic Vectors / genetics
  • Immune System / enzymology*
  • Immunity, Innate / immunology*
  • MAP Kinase Kinase Kinase 1*
  • MAP Kinase Kinase Kinases / genetics
  • MAP Kinase Kinase Kinases / immunology*
  • MAP Kinase Kinase Kinases / metabolism
  • Plant Diseases*
  • Plant Proteins / genetics
  • Plant Proteins / immunology*
  • Plant Proteins / metabolism
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / immunology*
  • Protein-Serine-Threonine Kinases / metabolism
  • RNA, Messenger / metabolism
  • Sequence Homology, Nucleic Acid
  • Signal Transduction / genetics
  • Tobacco / enzymology*
  • Tobacco / growth & development
  • Tobacco / immunology
  • Tobacco Mosaic Virus / genetics
  • Tobacco Mosaic Virus / immunology


  • BS2 protein, Capsicum chacoense
  • Plant Proteins
  • RNA, Messenger
  • Protein-Serine-Threonine Kinases
  • MAP Kinase Kinase Kinase 1
  • MAP Kinase Kinase Kinases
  • MAP3K1 protein, human
  • NPK1 protein, Nicotiana tabacum