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Inactivation of thioredoxin f 1 leads to decreased light activation of ADP‐glucose pyrophosphorylase and altered diurnal starch turnover in leaves of Arabidopsis plants
Author(s) -
THORMÄHLEN INA,
RUBER JOACHIM,
VON ROEPENACKLAHAYE EDDA,
EHRLICH SVENMATTHIAS,
MASSOT VINCENT,
HÜMMER CHRISTINE,
TEZYCKA JUSTYNA,
ISSAKIDISBOURGUET EMMANUELLE,
GEIGENBERGER PETER
Publication year - 2013
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2012.02549.x
Subject(s) - starch , chloroplast , biochemistry , sucrose , metabolite , arabidopsis , photosynthesis , chemistry , sucrose phosphate synthase , mutant , rubisco , thioredoxin , biology , enzyme , sucrose synthase , invertase , gene
Chloroplast thioredoxin f (Trx f ) is an important regulator of primary metabolic enzymes. However, genetic evidence for its physiological importance is largely lacking. To test the functional significance of Trx f in vivo , Arabidopsis mutants with insertions in the trx f 1 gene were studied, showing a drastic decrease in Trx f leaf content. Knockout of Trx f 1 led to strong attenuation in reductive light activation of ADP‐glucose pyrophosphorylase (AGPase), the key enzyme of starch synthesis, in leaves during the day and in isolated chloroplasts, while sucrose‐dependent redox activation of AGPase in darkened leaves was not affected. The decrease in light‐activation of AGPase in leaves was accompanied by a decrease in starch accumulation, an increase in sucrose levels and a decrease in starch‐to‐sucrose ratio. Analysis of metabolite levels at the end of day shows that inhibition of starch synthesis was unlikely due to shortage of substrates or changes in allosteric effectors. Metabolite profiling by gas chromatography–mass spectrometry pinpoints only a small number of metabolites affected, including sugars, organic acids and ethanolamine. Interestingly, metabolite data indicate carbon shortage in trx f1 mutant leaves at the end of night. Overall, results provide in planta evidence for the role played by Trx f in the light activation of AGPase and photosynthetic carbon partitioning in plants.