Redox regulation of gene expression by Rap2.4a. Nuclear expression of chloroplast antioxidant enzymes is redox-regulated by the modulation of the expression and changes in the quaternary structure of Rap2.4a. If the redox poise shifts to more oxidized values, Rap2.4a expression is increased. Rap2.4a protein dimerizes in response to the redox-shift (Fig. 4) and activates 2CPA expression. Under severe oxidative stress Rap2.4a expression is decreased and the transcription factor loses its DNA affinity and oligomerizes.