Short-Term High Temperature Alters psbA Gene Expression and D1 Protein Related Photosystem II Function in Rice Seedlings

High temperature disrupts physiological processes in rice, including impairing the function of photosystem II and leading to reduced productivity. However, understanding of the short-term effects of elevated temperatures on photosystem II function and its protein composition in rice seedlings remains limited. This study examined the effect of short-term exposure to elevated temperature (25°C–40°C) on photosystem II function, photosynthetic pigments, psbA gene expression and D1 protein in three rice seedlings, namely Dular, IR64 and KDML105. The findings revealed that a short-term temperature of 30°C–35°C activated photosystem II function, as reflected by improved photosystem II efficiency and increased levels of photosynthetic pigments. In contrast, a temperature of 40°C impaired and suppressed photosystem II function. A short-term temperature of 40°C activated the psbA gene expression and D1 protein synthesis in Dular, while inhibiting these processes in IR64 and KDML105. This suggested that short-term temperatures between 30°C and 35°C were ideal for photosystem II function at the metabolic level, whereas 40°C adversely affected photosystem II function. At the molecular level, Dular demonstrated rapidly repaired psbA gene expression and D1 protein synthesis, with high activity observed after short-term exposure to 40°C. Meanwhile, IR64 and KDML105 experienced significant molecular damage under the same conditions. These findings proved Dular as heat-tolerant, whereas IR64 and KDML105 were classified as heat-sensitive and moderately heat-sensitive, respectively.