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Chloroplast Trx f as a key actor in leaf starch synthesis

AuthorsSanz Barrio, Ruth; Corral-Martínez, Patricia; Seguí-Simarro, José María ; Farrán, Inmaculada
Issue Date2011
PublisherSociedad Española de Fisiología Vegetal
CitationXII Congreso Hispano-Luso de Fisiología Vegetal (2011)
AbstractStarch means the principal storage carbohydrate in higher plants. It is synthesized in plastids in both photosynthetic and non-photosynthetic cells. In leaves, a part of the photosynthetically fixed carbon is retained in the chloroplasts to synthesize starch as a transient carbon store, which is remobilised during the night to support non-photosynthetic leaf metabolism and sucrose export. Regulation of starch synthesis in leaves may occur in a similar way as the lightdependent regulation of Calvin cycle enzymes, where reduced Trxs act as activators. Plastid thioredoxins f and m (Trx f and Trx m) were originally identified as light dependent regulators of several carbon metabolism enzymes. Redox signals generated by the photosynthetic electron transport chain in response to light, are involved in the regulation of Calvin cycle enzymes, carbon storage and partitioning in plants. The role of Trx f and Trx m in the activation of Calvin cycle enzymes is best known among the Trx family, and many biochemical and proteomic studies have increased the number of target enzymes and processes regulated by these Trxs. However, a functional distinction between the two types has not always been clearly determined in investigations under different in vitro conditions. The major question asked in the present work was whether Trx f or Trx m could be equally efficient modulating carbon metabolism enzymes in leaves. For that purpose we have investigated the effect of Trx f or Trx m overexpression in tobacco chloroplasts focused on carbon metabolism and storage. Only overexpression of Trx f is able to dramatically increase starch accumulation in tobacco leaves (up to 10-fold), clearly depending on Trx f levels in tobacco plants. Starch accumulation in overexpressing Trx f plants did not follow diurnal pattern, being starch levels at night similar to day. Sugar levels were also increased, although followed diurnal pattern similar to the wild type. Now we are focused on identifying which of the redox-dependent enzymes were activated in overexpressing Trx f plants and led to its starchy phenotype.
DescriptionTrabajo presentado en el XII Congreso Hispano-Luso de Fisiología Vegetal, celebrado en Castellón del 21 al 24 de junio de 2011.
Appears in Collections:(IDAB) Comunicaciones congresos
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