title: Plastid movement impaired 2, a new gene involved in normal blue-light-induced chloroplast movements in Arabidopsis.
abstract: Chloroplasts move in a light-dependent manner that can modulate the photosynthetic potential of plant cells. Identification of genes required for light-induced chloroplast movement is beginning to define the molecular machinery that controls these movements. In this work, we describe plastid movement impaired 2 (pmi2), a mutant in Arabidopsis (Arabidopsis thaliana) that displays attenuated chloroplast movements under intermediate and high light intensities while maintaining a normal movement response under low light intensities. In wild-type plants, fluence rates below 20 micromol m(-2) s(-1) of blue light lead to chloroplast accumulation on the periclinal cell walls, whereas light intensities over 20 micromol m(-2) s(-1) caused chloroplasts to move toward the anticlinal cell walls (avoidance response). However, at light intensities below 75 micromol m(-2) s(-1), chloroplasts in pmi2 leaves move to the periclinal walls; 100 micromol m(-2) s(-1) of blue light is required for chloroplasts in pmi2 to move to the anticlinal cell walls, indicating a shift in the light threshold for the avoidance response in the mutant. The pmi2 mutation has been mapped to a gene that encodes a protein of unknown function with a large coiled-coil domain in the N terminus and a putative P loop. PMI2 shares sequence and structural similarity with PMI15, another unknown protein in Arabidopsis that, when mutated, causes a defect in chloroplast avoidance under high-light intensities.
authors.affiliation: Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
authors.forename: Darron R
authors.initials: DR
authors.lastname: Luesse
authors.forename: Stacy L
authors.initials: SL
authors.lastname: DeBlasio
authors.forename: Roger P
authors.initials: RP
authors.lastname: Hangarter
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002736:Chloroplasts / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D019913:Nuclear Localization Signals; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D029681:Arabidopsis Proteins; D019913:Nuclear Localization Signals; C514756:PMI2 protein, Arabidopsis