Photo-Oxidative Stress in Plants: ROS Signaling, Damage Propagation, and Systems-Level Resilience

Photo-oxidative stress, resulting from an imbalance between light absorption and photosynthetic carbon utilization, poses a fundamental challenge to plant survival and productivity. This review synthesizes recent advances to present an integrated framework connecting reactive oxygen species (ROS) signaling, damage propagation, and systems-level resilience. We move beyond describing ROS as mere toxic byproducts to position them as central hubs in a complex, interconnected network. We integrate the specific sites of ROS generation, particularly ¹O₂ at PSII and H₂O₂ at PSI, with their distinct retrograde signaling pathways (e.g., EXECUTER, β-cyclocitral, and RES/RCS pathways) that reprogram nuclear gene expression. A systems perspective is then applied to reveal how initial photochemical damage propagates through a self-amplifying "vicious cycle" of impaired photosystem repair, lipid peroxidation, and protein oxidation, ultimately threatening cellular integrity. Counteracting this cycle is a multi-layered photoprotective arsenal including NPQ, alternative electron sinks (CEF, WWC), and an integrated antioxidant network, which we re-evaluate not as independent modules but as a coordinated, evolutionary-tuned defense system. We synthesize this knowledge to highlight a central paradigm for crop improvement: the pervasive growth-defense trade-off. Investment in photoprotection, while crucial for survival, diverts resources from yield, explaining why single-gene modifications often fail in the field. Therefore, we argue that future strategies must move beyond simply enhancing single components and instead focus on "optimizing the network". We conclude by outlining how synthetic biology, multi-omics integration, and genomics-assisted breeding can be leveraged to fine-tune this integrated system, aiming to develop climate-resilient crops that balance productivity with survival in an increasingly volatile climate.