title: A plant-specific protein essential for blue-light-induced chloroplast movements.
abstract: In Arabidopsis (Arabidopsis thaliana), light-dependent chloroplast movements are induced by blue light. When exposed to low fluence rates of light, chloroplasts accumulate in periclinal layers perpendicular to the direction of light, presumably to optimize light absorption by exposing more chloroplast area to the light. Under high light conditions, chloroplasts become positioned parallel to the incoming light in a response that can reduce exposure to light intensities that may damage the photosynthetic machinery. To identify components of the pathway downstream of the photoreceptors that mediate chloroplast movements (i.e. phototropins), we conducted a mutant screen that has led to the isolation of several Arabidopsis mutants displaying altered chloroplast movements. The plastid movement impaired1 (pmi1) mutant exhibits severely attenuated chloroplast movements under all tested fluence rates of light, suggesting that it is a necessary component for both the low- and high-light-dependant chloroplast movement responses. Analysis of pmi1 leaf cross sections revealed that regardless of the light condition, chloroplasts are more evenly distributed in leaf mesophyll cells than in the wild type. The pmi1-1 mutant was found to contain a single nonsense mutation within the open reading frame of At1g42550. This gene encodes a plant-specific protein of unknown function that appears to be conserved among angiosperms. Sequence analysis of the protein suggests that it may be involved in calcium-mediated signal transduction, possibly through protein-protein interactions.
authors.affiliation: Department of Biology, Indiana University, Bloomington, 47405, USA.
authors.forename: Stacy L
authors.initials: SL
authors.lastname: DeBlasio
authors.forename: Darron L
authors.initials: DL
authors.lastname: Luesse
authors.forename: Roger P
authors.initials: RP
authors.lastname: Hangarter
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000502:physiology* / Q000528:radiation effects*; D003116:Color; D003599:Cytoskeleton / Q000737:chemistry / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008027:Light; D008969:Molecular Sequence Data; D009068:Movement / Q000528:radiation effects*; D009154:Mutation; D018515:Plant Leaves / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D000199:Actins; D029681:Arabidopsis Proteins; D047908:Intracellular Signaling Peptides and Proteins; C507141:Pmi1 protein, Arabidopsis