Temperature–Photoperiod Interaction in Rice Phenology for Climate Adaptation: Insights Into Glycerate-Associated Metabolic Responses

Rice heading date is tightly regulated by photoperiod and temperature, which are critical environmental cues for climate adaptation. While photoperiodic control of flowering has been well characterized, the molecular and metabolic mechanisms underlying temperature responses and their interaction with photoperiod remain unclear. In this study, we used two Oryza sativa ssp. japonica cultivars under controlled conditions to investigate the effects of temperature (22°C vs. 28°C) and photoperiod (12 vs. 14.5 h) during the photo-sensitive period. Integrative transcriptomic and metabolomic analyses identified key regulators of heading time, with particular focus on glycerate metabolism. Thermosensitivity increased threefold under short-day conditions, while photosensitivity was enhanced under high temperature. Glycerate, a pivotal intermediate in photorespiration and glycolysis, showed an inverse correlation with days to heading and accumulated more strongly in leaves under short-day and high-temperature conditions. Exogenous glycerate application (250–500 μM) accelerated heading by 4–5 days, supporting its functional role in floral induction. These findings highlight glycerate- and serine-associated metabolic pathways in regulating heading responses to environmental cues, providing new perspectives for optimizing heading time and enhancing climate resilience in rice production.