title: A novel MAP kinase regulates flagellar length in Chlamydomonas.
abstract: Little is known about the molecular basis of organelle size control in eukaryotes. Cells of the biflagellate alga Chlamydomonas reinhardtii actively maintain their flagella at a precise length. Chlamydomonas mutants that lose control of flagellar length have been isolated and used to demonstrate that a dynamic process keeps flagella at an appropriate length. To date, none of the proteins required for flagellar length control have been identified in any eukaryotic organism. Here, we show that a novel MAP kinase is crucial to enforcing wild-type flagellar length in C. reinhardtii. Null mutants of LF4 [2], a gene encoding a protein with extensive amino acid sequence identity to a mammalian MAP kinase of unknown function, MOK [3], are unable to regulate the length of their flagella. The LF4 protein (LF4p) is localized to the flagella, and in vitro enzyme assays confirm that the protein is a MAP kinase. The long-flagella phenotype of lf4 cells is rescued by transformation with the cloned LF4 gene. The demonstration that a novel MAP kinase helps enforce flagellar length control indicates that a previously unidentified signal transduction pathway controls organelle size in C. reinhardtii.
authors.affiliation: Department of Plant Biology, University of Minnesota, 250 Biological Sciences Center, St. Paul, MN 55108, USA.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Berman
authors.forename: Nedra F
authors.initials: NF
authors.lastname: Wilson
authors.forename: Nancy A
authors.initials: NA
authors.lastname: Haas
authors.forename: Paul A
authors.initials: PA
authors.lastname: Lefebvre
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015139:Blotting, Southern; D016825:Chlamydomonas reinhardtii / Q000378:metabolism*; D005407:Flagella / Q000378:metabolism* / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D020928:Mitogen-Activated Protein Kinases