title: Integrated role of ROS and Ca+2in blue light-induced chloroplast avoidance movement in leaves of Hydrilla verticillata (L.f.) Royle.
abstract: Directional chloroplast photorelocation is a major physio-biochemical mechanism that allows these organelles to realign themselves intracellularly in response to the intensity of the incident light as an adaptive response. Signaling processes involved in blue light (BL)-dependent chloroplast movements were investigated in Hydrilla verticillata (L.f.) Royle leaves. Treatments with antagonists of actin filaments [2,3,5-triiodobenzoic acid (TIBA)] and microtubules (oryzalin) revealed that actin filaments, but not microtubules, play a pivotal role in chloroplast movement. Involvement of reactive oxygen species (ROS) in controlling chloroplast avoidance movement has been demonstrated, as exogenous H2O2not only accelerated chloroplast avoidance but also could induce chloroplast avoidance even in weak blue light (WBL). Further support came from experiments with different ROS scavengers, i.e., dimethylthiourea (DMTU), KI, and CuCl2, which inhibited chloroplast avoidance, and from ROS localization using specific stains. Such avoidance was also partially inhibited by ZnCl2, an inhibitor of NADPH oxidase (NOX) as well as 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), a photosynthetic electron transport chain (ETC) inhibitor at PS II. However, methyl viologen (MV), a PS I ETC inhibitor, rather accelerated avoidance response. Exogenous calcium (Ca+2) induced avoidance even in WBL while inhibited chloroplast accumulation partially. On the other hand, chloroplast movements (both accumulation and avoidance) were blocked by Ca+2antagonists, La3+(inhibitor of plasma membrane Ca+2channel) and ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA, Ca+2chelator) while LiCl that affects Ca+2release from endosomal compartments did not show any effect. A model on integrated role of ROS and Ca+2(influx from apolastic space) in actin-mediated chloroplast avoidance has been proposed.
authors.affiliation: Plant Physiology and Biochemistry Laboratory, Department of Botany, Visva-Bharati University, Santiniketan, 731235, West Bengal, India.
authors.forename: Arkajo
authors.initials: A
authors.lastname: Majumdar
authors.affiliation: Plant Physiology and Biochemistry Laboratory, Department of Botany, Visva-Bharati University, Santiniketan, 731235, West Bengal, India. rupkumar.kar@visva-bharati.ac.in.
authors.forename: Rup Kumar
authors.initials: RK
authors.lastname: Kar
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D004136:Dinitrobenzenes / Q000494:pharmacology; D004579:Electron Transport / Q000528:radiation effects; D006706:Homeostasis / Q000187:drug effects / Q000528:radiation effects; D031321:Hydrocharitaceae / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects*; D006861:Hydrogen Peroxide / Q000633:toxicity; D008027:Light; D009068:Movement / Q000528:radiation effects; D010788:Photosynthesis / Q000187:drug effects / Q000528:radiation effects; D010797:Phthalimides / Q000494:pharmacology; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013424:Sulfanilamides / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D014283:Triiodobenzoic Acids / Q000494:pharmacology
chemical_list: D004136:Dinitrobenzenes; D010797:Phthalimides; D017382:Reactive Oxygen Species; D013424:Sulfanilamides; D014283:Triiodobenzoic Acids; D013481:Superoxides; C002687:alpha-naphthylphthalamic acid; C012465:oryzalin; D006861:Hydrogen Peroxide; C052968:2,3,5-triiodobenzoic acid; D002118:Calcium
keywords: Blue light; Calcium; Chloroplast movements; ROS; Signal transduction