Shifting paradigms and novel players in Cys-based redox regulation and ROS signaling in plants - and where to go next

Cys-based redox regulation was long regarded a major adjustment mechanism of photosynthesis and metabolism in plants, but in the recent years, its scope has broadened to most fundamental processes of plant life. Drivers of the recent surge in new insights into plant redox regulation have been the availability of the genome-scale information combined with technological advances such as quantitative redox proteomics and in vivo biosensing. Several unexpected findings have started to shift paradigms of redox regulation. Here, we elaborate on a selection of recent advancements, and pinpoint emerging areas and questions of redox biology in plants. We highlight the significance of (1) proactive H₂O₂ generation, (2) the chloroplast as a unique redox site, (3) specificity in thioredoxin complexity, (4) how to oxidize redox switches, (5) governance principles of the redox network, (6) glutathione peroxidase-like proteins, (7) ferroptosis, (8) oxidative protein folding in the ER for phytohormonal regulation, (9) the apoplast as an unchartered redox frontier, (10) redox regulation of respiration, (11) redox transitions in seed germination and (12) the mitochondria as potential new players in reductive stress safeguarding. Our emerging understanding in plants may serve as a blueprint to scrutinize principles of reactive oxygen and Cys-based redox regulation across organisms.