The MAP kinase cascade that includes MAPKKK-related protein kinase NPK1 controls a mitotic proces in plant cells.
The tobacco NPK1 cDNA was the first-isolated plant cDNA for a homolog of mitogen-activated protein kinase kinase kinases (MAPKKKs). The kinase domain of the NPK1 protein can replace the functions of MAPKKKs in yeasts, while the amino acid sequence of the kinase-unrelated region does not have any homology to those of MAPKKKs from other organisms. Transcription of the NPK1 gene takes place in meristematic tissues or immature organs in a tobacco plant. During a tobacco cell cycle, transcriptional and translational products of NPK1 are present from S to M phase and decrease after the M phase. Expression of the NACK1 gene, which is predicted to encode a novel kinesin-like microtubule-based motor protein capable of activating NPK1, is specific to M phase, suggesting that activation of NPK1 occurs in M phase. Characterization of cDNAs for a MAPKK and a MAPK which can act downstream of NPK1 makes a proposition that the MAP kinase pathway involving NPK1 regulates a mitotic process associated with microtubules.
Nishihama
R
R
Laboratory of Plant Development, Graduate School of Science, Nagoya University, Japan.
Machida
Y
Y
D005656:Fungal Proteins / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D020930:MAP Kinase Kinase Kinases / Q000235:genetics*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008938:Mitosis / Q000502:physiology*; D008969:Molecular Sequence Data; D010947:Plants, Toxic; D017346:Protein Serine-Threonine Kinases; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics*
D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; C075981:KIN3 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D020930:MAP Kinase Kinase Kinases