title: Chlorophyll antenna size adjustments by irradiance in Dunaliella salina involve coordinate regulation of chlorophyll a oxygenase (CAO) and Lhcb gene expression.
abstract: To elucidate the mechanism of irradiance-dependent adjustments in the chlorophyll antenna size of photosynthesis, we addressed the regulation of expression of genes encoding a variety of chlorophyll biosynthesis enzymes and that of the Lhcb genes in the model organism Dunaliella salina. Among the chlorophyll biosynthesis enzymes tested, only the chlorophyll a oxygenase (CAO) gene responded to changes in the level of irradiance with substantial mRNA level and kinetics of change that were similar to those of the Lhcb genes. Evidence is presented for the operation of a cytosolic signal transduction pathway for the rapid (order of minutes) regulation of both CAO and Lhcb gene expression by irradiance. Inhibitor studies and transient activation of Ca2+-dependent kinase suggested phopholipase-C activation to Ca2+ release, and activation of a specific Ca2+/CaM-dependent protein kinase in this cytosolic signal transduction pathway. The redox state of the plastoquinone pool also serves to regulate CAO and Lhcb gene expression on a slower time scale (hours) and probably serves as a plastidic-origin signal that acts coordinately with the cytosolic signal transduction pathway. It is proposed that irradiance-dependent adjustments in the chlorophyll antenna size occur by coordinate regulation of CAO and Lhcb gene expression via two distinct signal transduction pathways in photosynthetic organisms.
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan.
authors.forename: Tatsuru
authors.initials: T
authors.lastname: Masuda
authors.forename: Ayumi
authors.initials: A
authors.lastname: Tanaka
authors.forename: Anastasios
authors.initials: A
authors.lastname: Melis
mesh_terms: D020418:Algal Proteins / Q000235:genetics* / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002734:Chlorophyll / Q000378:metabolism*; D000460:Chlorophyta / Q000235:genetics / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000528:radiation effects; D010105:Oxygenases / Q000235:genetics* / Q000378:metabolism; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010788:Photosynthesis / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011760:Pyrrolidinones / Q000494:pharmacology; D020871:RNA Stability / Q000187:drug effects / Q000528:radiation effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D019311:Staurosporine / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects / Q000528:radiation effects; D014268:Trifluoperazine / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors
chemical_list: D020418:Algal Proteins; D002147:Calmodulin; D004791:Enzyme Inhibitors; D004963:Estrenes; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; D012333:RNA, Messenger; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D002734:Chlorophyll; C074854:U 73343; D014268:Trifluoperazine; D010105:Oxygenases; C115272:chlorophyll a oxygenase; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010738:Type C Phospholipases; D019311:Staurosporine