title: Redox activity of thioredoxin z and fructokinase-like protein 1 is dispensable for autotrophic growth of Arabidopsis thaliana.
abstract: Redox modulation of protein activity by thioredoxins (TRXs) plays a key role in cellular regulation. Thioredoxin z (TRX z) and its interaction partner fructokinase-like protein 1 (FLN1) represent subunits of the plastid-encoded RNA polymerase (PEP), suggesting a role of both proteins in redox regulation of chloroplast gene expression. Loss of TRX z or FLN1 expression generates a PEP-deficient phenotype and renders the plants incapable to grow autotrophically. This study shows that PEP function in trx z and fln1 plants can be restored by complementation with redox-inactive TRX z C106S and FLN1 C105/106A protein variants, respectively. The complemented plants showed wild-type levels of chloroplast gene expression and were restored in photosynthetic capacity, indicating that redox regulation of PEP through TRX z/FLN1 per se is not essential for autotrophic growth. Promoter-reporter gene studies indicate that TRX z and FLN1 are expressed during early phases of leaf development while expression ceases at maturation. Taken together, our data support a model in which TRX z and FLN1 are essential structural components of the PEP complex and their redox activity might only play a role in the fine tuning of PEP function.
authors.affiliation: Friedrich-Alexander-Universität, Department of Biology, Division of Biochemistry, Staudtstr. 5, 91058 Erlangen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Wimmelbacher
authors.affiliation: Leibniz-Institute of Vegetable and Ornamental Crops (IGZ), Theodor-Echtermeyer-Weg 1, 14979 Großbeeren, Germany Institute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany boernke@igzev.de.
authors.forename: Frederik
authors.initials: F
authors.lastname: Börnke
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D052818:Autotrophic Processes; D054479:Chloroplast Thioredoxins / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D010084:Oxidation-Reduction; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018087:Plastids / Q000201:enzymology / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D054479:Chloroplast Thioredoxins; C580812:thioredoxin z, Arabidopsis; C000594290:FLN1 protein, Arabidopsis; D017853:Phosphotransferases (Alcohol Group Acceptor); D012321:DNA-Directed RNA Polymerases
keywords: Chloroplast transcription; FLN1; TRX z.; plastid-encoded RNA polymerase; redox regulation; thioredoxins