A semidominant mutation in an Arabidopsis mitogen-activated protein kinase phosphatase-like gene compromises cortical microtubule organization.
Reversible protein phosphorylation regulates many cellular processes, including the dynamics and organization of the microtubule cytoskeleton, but the events mediating it are poorly understood. A semidominant phs1-1 allele of the Arabidopsis thaliana PROPYZAMIDE-HYPERSENSITIVE 1 locus exhibits phenotypes indicative of compromised cortical microtubule functions, such as left-handed helical growth of seedling roots, defective anisotropic growth at low doses of microtubule-destabilizing drugs, enhancement of the temperature-sensitive microtubule organization1-1 phenotype, and less ordered and more fragmented cortical microtubule arrays compared with the wild type. PHS1 encodes a novel protein similar to mitogen-activated protein kinase (MAPK) phosphatases. In phs1-1, a conserved Arg residue in the noncatalytic N-terminal region is exchanged with Cys, and the mutant PHS1 retained considerable phosphatase activity in vitro. In mammalian MAPK phosphatases, the corresponding region serves as a docking motif for MAPKs, and analogous Arg substitutions severely inhibit the kinase-phosphatase association. Transgenic studies indicate that the phs1-1 mutation acts dominant negatively, whereas the null phs1-2 allele is recessive embryonic lethal. We propose that the PHS1 phosphatase regulates more than one MAPK and that a subset of its target kinases is involved in the organization of cortical microtubules.
Naoi
Kuniko
K
Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, 630-0192, Japan.
Hashimoto
Takashi
T
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics*; D003470:Culture Media; D054638:Dual Specificity Phosphatase 1; D017343:Genes, Plant; D008855:Microscopy, Electron, Scanning; D008870:Microtubules / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D010802:Phylogeny; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure; D030821:Plants, Genetically Modified; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000235:genetics*; D036226:Seedlings / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure
D029681:Arabidopsis Proteins; D003470:Culture Media; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C514675:PHS1 protein, Arabidopsis; D017027:Protein Tyrosine Phosphatases