Systematic monitoring of photosynthetically-derived oxidative signals by a peroxiredoxin-based biosensor

Transmission of reductive cues from the photosynthetic electron transport chain to redox-regulated proteins plays a crucial role in activating chloroplast metabolism. However, deciphering the role of their counterbalanced oxidative signals is challenging due to monitoring difficulties. Here, we demonstrate the light-depended redox modification of chloroplast targeted 2-Cys peroxiredoxins and introduced a peroxiredoxin-based biosensor to monitor the dynamic changes in photosynthetically-derived oxidative signals. Systematic monitoring of probe oxidation demonstrated the induction of oxidative signals under habitual light intensities and their inverse relationship with chloroplastic NADPH levels, unraveling the combined activity of reducing and oxidizing signals in fine-tuning chloroplast activity. Considering that peroxiredoxins mediate oxidative inhibition of carbon assimilation, the measured light-dependent oxidative signals reflect the limitation to photosynthesis imposed by the redox regulatory system.A genetically encoded biosensor unmasked the dominant role of photosynthetically-derived oxidative signals under habitual conditions.