title: Deletion of chloroplast NADPH-dependent thioredoxin reductase results in inability to regulate starch synthesis and causes stunted growth under short-day photoperiods.
abstract: Plastid-localized NADPH-dependent thioredoxin reductase C (NTRC) is a unique NTR enzyme containing both reductase and thioredoxin domains in a single polypeptide. Arabidopsis thaliana NTRC knockout lines (ntrc) show retarded growth, especially under short-day (SD) photoperiods. This study identified chloroplast processes that accounted for growth reduction in SD-acclimated ntrc. The strongest reduction in ntrc growth occurred under photoperiods with nights longer than 14 h, whereas knockout of the NTRC gene did not alter the circadian-clock-controlled growth of Arabidopsis. Lack of NTRC modulated chloroplast reactive oxygen species (ROS) metabolism, but oxidative stress was not the primary cause of retarded growth of SD-acclimated ntrc. Scarcity of starch accumulation made ntrc leaves particularly vulnerable to photoperiods with long nights. Direct interaction of NTRC and ADP-glucose pyrophosphorylase, a key enzyme in starch synthesis, was confirmed by yeast two-hybrid analysis. The ntrc line was not able to maximize starch synthesis during the light period, which was particularly detrimental under SD conditions. Acclimation of Arabidopsis to SD conditions also involved an inductive rise of ROS production in illuminated chloroplasts that was not counterbalanced by the activation of plastidial anti-oxidative systems. It is proposed that knockout of NTRC challenges redox regulation of starch synthesis, resulting in stunted growth of the mutant lines acclimated to the SD photoperiod.
authors.affiliation: Molecular Plant Biology, Department of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland.
authors.forename: Anna
authors.initials: A
authors.lastname: Lepistö
authors.forename: Eveliina
authors.initials: E
authors.lastname: Pakula
authors.forename: Jouni
authors.initials: J
authors.lastname: Toivola
authors.forename: Anja
authors.initials: A
authors.lastname: Krieger-Liszkay
authors.forename: Florence
authors.initials: F
authors.lastname: Vignols
authors.forename: Eevi
authors.initials: E
authors.lastname: Rintamäki
mesh_terms: D000064:Acclimatization; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism; D051599:Glucose-1-Phosphate Adenylyltransferase / Q000378:metabolism; D018384:Oxidative Stress; D017440:Photoperiod; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013213:Starch / Q000096:biosynthesis*; D013880:Thioredoxin-Disulfide Reductase / Q000235:genetics* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D017382:Reactive Oxygen Species; D013213:Starch; D013880:Thioredoxin-Disulfide Reductase; D051599:Glucose-1-Phosphate Adenylyltransferase
keywords: ADP-glucose pyrophosphorylase; Arabidopsis thaliana; NTRC; ROS; chloroplast; starch; thioredoxins.