Decoding redox pathways in plants: Structural and functional comparison of peroxiredoxins and glutathione peroxidases

Plants face constant environmental challenges that lead to fluctuations in intracellular reactive oxygen species (ROS) levels. Among these, hydrogen peroxide (H₂O₂) stands out as a stable and diffusible signaling molecule that modulates the redox state of key proteins. To prevent oxidative damage while maintaining signaling functions, plants rely on thiol peroxidases (TPXs), particularly glutathione peroxidase-like proteins (GPXLs) and peroxiredoxins (PRXs). Both enzyme families catalyze peroxide reduction and share thiol-based redox mechanisms, seemingly converging on similar functions. This review highlights both the convergence and, more importantly, the divergence between GPXLs and PRXs in plants, including their evolutionary histories, domain architectures, and substrate and reductant specificities. While 2-Cys PRXs are well-established redox sensors capable of relaying oxidative signals to target proteins or via thioredoxin networks, relatively few examples have confirmed that GPXLs can also oxidize specific target proteins, positioning them as potential redox signal transducers. We explore documented cases of GPXL- and PRX-mediated redox signaling in stress responses and emphasize the need for further investigation into TPX interactomes and posttranslational modifications. Unraveling the distinct and overlapping functions of PRXs and GPXLs will provide deeper insight into how plants fine-tune redox signals to cope with environmental stress.