Redox control of flowering

Reactive oxygen species signaling in melatonin-mediated plant stress response

Reactive oxygen species (ROS) are crucial signaling molecules in plants that play multifarious roles in prompt response to environmental stimuli. Despite the classical thoughts that ROS are toxic when accumulate in excess, recent advances in plant ROS signaling biology reveal that ROS participate in biotic and abiotic stress perception, signal integration, and stress-response network activation, hence contributing to plant defense and stress tolerance. ROS production, scavenging and transport are fine-tuned by plant hormones and stress-response signaling pathways. Crucially, the emerging plant hormone melatonin attenuates excessive ROS accumulation under stress, whereas ROS signaling mediates melatonin-induced plant developmental response and stress tolerance. In particular, RESPIRATORY BURST OXIDASE HOMOLOG (RBOH) proteins responsible for apoplastic ROS generation act downstream of melatonin to mediate stress response. In this review, we discuss promising developments in plant ROS signaling and how ROS might mediate melatonin-induced plant resilience to environmental stress.

Systemic H2O2 signaling mediates epigallocatechin-3-gallate-induced cadmium tolerance in tomato

Toxic heavy metal cadmium (Cd) reduces crop yield and threatens human health via the food chain. The bioactive flavonoid 'Epigallocatechin-3-gallate' (EGCG) affects plant stress response; however, the function of EGCG in Cd tolerance and the molecular pathways remain largely unknown. Here, we revealed that root application of EGCG alleviated Cd stress in tomato plants. While Cd stress decreased Fv/Fm, Ф_PSII, photosynthetic rate, root growth, root vitality and biomass accumulation by increasing reactive oxygen species (ROS) accumulation and lipid peroxidation, exogenous EGCG minimized excessive ROS accumulation and oxidative stress by promoting the activity of antioxidant enzymes and redox poise in roots and leaves. Moreover, EGCG induced the transcript of RESPIRATORY BURST OXIDASE HOMOLOG1 (RBOH1) and decreased Cd content and photoinhibition in leaves. Interestingly, similar to EGCG, exogenous H₂O₂ application also enhanced Cd tolerance; however, the application of an NADPH oxidase inhibitor, diphenyleneiodonium (DPI), aggravated Cd phytotoxicity and attenuated the beneficial effects of EGCG on plant tolerance to Cd stress, suggesting that root applied EGCG-induced expression of RBOH1 and associated H₂O₂ signaling mediate the EGCG-induced enhanced Cd tolerance. This work elucidates a fundamental mechanism behind EGCG-mediated Cd tolerance and contributes to our existing knowledge of stress resistance properties of EGCG in plants.