title: Chloroplastic thioredoxin m functions as a major regulator of Calvin cycle enzymes during photosynthesis in vivo.
abstract: Thioredoxins (Trxs) regulate the activity of various chloroplastic proteins in a light-dependent manner. Five types of Trxs function in different physiological processes in the chloroplast of Arabidopsis thaliana. Previous in vitro experiments have suggested that the f-type Trx (Trx f) is the main redox regulator of chloroplast enzymes, including Calvin cycle enzymes. To investigate the in vivo contribution of each Trx isoform to the redox regulatory system, we first quantified the protein concentration of each Trx isoform in the chloroplast stroma. The m-type Trx (Trx m), which consists of four isoforms, was the most abundant type. Next, we analyzed several Arabidopsis Trx-m-deficient mutants to elucidate the physiological role of Trx m in vivo. Deficiency of Trx m impaired plant growth and decreased the CO2 assimilation rate. We also determined the redox state of Trx target enzymes to examine their photo-reduction, which is essential for enzyme activation. In the Trx-m-deficient mutants, the reduction level of fructose-1,6-bisphosphatase and sedoheptulose-1,7-bisphosphatase was lower than that in the wild type. Inconsistently with the historical view, our in vivo study suggested that Trx m plays a more important role than Trx f in the activation of Calvin cycle enzymes.
authors.affiliation: Department of Bioresource and Environmental Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Kamigamo Motoyama, Kita-ku, Kyoto, 603-8555, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Okegawa
authors.affiliation: Department of Bioresource and Environmental Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Kamigamo Motoyama, Kita-ku, Kyoto, 603-8555, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Motohashi
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism; D054479:Chloroplast Thioredoxins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D002736:Chloroplasts / Q000378:metabolism*; D004789:Enzyme Activation; D009154:Mutation; D010084:Oxidation-Reduction; D010788:Photosynthesis; D020033:Protein Isoforms / Q000378:metabolism / Q000502:physiology; D034622:RNA Interference
chemical_list: D029681:Arabidopsis Proteins; D054479:Chloroplast Thioredoxins; D020033:Protein Isoforms; D002245:Carbon Dioxide; D000255:Adenosine Triphosphate
keywords: Arabidopsis thaliana; Calvin cycle; chloroplast thioredoxin; in vivo; redox regulation