Abstract
Thioredoxin (Trx) is reduced following electron transports to activate the Calvin cycle, while glutathione is a tripeptide reductant that is synthesized following electron transports. We have recently found new regulation of the Calvin cycle: fructose-1,6-bisphosphate aldolase (FBA) is downregulated by Trx and upregulation by glutathionylation. Here we present the details of the regulation. Glutathionylation of FBA occurs in response to illumination, and reduced expression of the FBA decreases growth and CO2 fixation. Overexpression of the FBA leads not only to the promotion of growth and CO2 fixation but also to increase in Rubisco contents per chlorophylls. Thus, glutathionylation of FBA not simply functions as a switch of one reaction, but also contributes to other regulation of the Calvin cycle. Two cysteine residues participate in glutathionylation, but another cysteine residue also contributes to growth promotion, suggesting that, in addition to glutathionylation, FBA is redox-regulated in vivo.
