title: Type-f thioredoxins have a role in the short-term activation of carbon metabolism and their loss affects growth under short-day conditions in Arabidopsis thaliana.
abstract: Redox regulation plays a central role in the adaptation of chloroplast metabolism to light. Extensive biochemical analyses in vitro have identified f-type thioredoxins (Trxs) as the most important catalysts for light-dependent reduction and activation of the enzymes of the Calvin-Benson cycle. However, the precise function of type f Trxs in vivo and their impact on plant growth are still poorly known. To address this issue we have generated an Arabidopsis thaliana double knock-out mutant, termed trxf1f2, devoid of both f1 and f2 Trxs. Despite the essential function previously proposed for f-type Trxs, the visible phenotype of the trxf1f2 double mutant was virtually indistinguishable from the wild type when grown under a long-day photoperiod. However, the Trx f-deficient plants showed growth inhibition under a short-day photoperiod which was not rescued at high light intensity. The absence of f-type Trxs led to significantly lower photosynthetic electron transport rates and higher levels of non-photochemical energy quenching. Notably, the Trx f null mutant suffered from a shortage of photosystem I electron acceptors and delayed activation of carbon dioxide fixation following a dark-light transition. Two redox-regulated Calvin-Benson cycle enzymes, fructose 1,6-bisphosphatase (FBPase) and Rubisco activase, showed retarded and incomplete reduction in the double mutant upon illumination, compared with wild-type plants. These results show that the function of f-type Trxs in the rapid activation of carbon metabolism in response to light is not entirely compensated for by additional plastid redox systems, and suggest that these Trxs have an important role in the light adjustment of photosynthetic metabolism.
authors: Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla and CSIC, Avda Américo Vespucio, 49, 41092-Sevilla, Spain.
authors: Belén
authors: B
authors: Naranjo
authors: Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, Avda Reina Mercedes, 10, 41012-Sevilla, Spain.
authors: Antonio
authors: A
authors: Diaz-Espejo
authors: Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla and CSIC, Avda Américo Vespucio, 49, 41092-Sevilla, Spain.
authors: Marika
authors: M
authors: Lindahl
authors: Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla and CSIC, Avda Américo Vespucio, 49, 41092-Sevilla, Spain fjcejudo@us.es.
authors: Francisco Javier
authors: http://orcid.org/0000-0002-3936-5491
authors: FJ
authors: Cejudo
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D054479:Chloroplast Thioredoxins / Q000378:metabolism*; D004579:Electron Transport / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D007700:Kinetics; D008027:Light; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction / Q000528:radiation effects; D017440:Photoperiod; D010788:Photosynthesis / Q000528:radiation effects; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D063245:Plant Development / Q000528:radiation effects; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D054479:Chloroplast Thioredoxins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D012333:RNA, Messenger; C545839:Rca protein, Arabidopsis; D002245:Carbon Dioxide; D002244:Carbon
keywords: Carbon assimilation; chloroplast; fructose 1,6 bisphosphatase; photosynthesis; redox regulation; thioredoxin.