Cytosolic, mitochondrial thioredoxins and thioredoxin reductases in Arabidopsis thaliana.

Thioredoxins, by reducing disulfide bridges are one of the main participants that regulate cellular redox balance. In plants, the thioredoxin system is particularly complex. The most well-known thioredoxins are the chloroplastic ones, that participate in the regulation of enzymatic activities during the transition between light and dark phases. The mitochondrial system composed of NADPH-dependent thioredoxin reductase and type o thioredoxin has only recently been described. The type h thioredoxin group is better known. Yeast complementation experiments demonstrated that Arabidopsis thaliana thioredoxins h have divergent functions, at least in Saccharomyces cerevisiae. They have diverse affinities for different target proteins, most probably because of structural differences. However, plant thioredoxin h functions still have to be defined.