Moderate soil drying mitigates high temperature-induced spikelet opening impairment by enhancing jasmonates accumulation in lodicules of photo-thermosensitive male-sterile rice

This study investigated the role of jasmonates (JAs) in mitigating high temperature (HT) stress-induced spikelet opening impairment in photo-thermosensitive genetic male-sterile (PTGMS) rice under controlled moderate soil drying (MD). Two PTGMS rice varieties were grown under normal temperature (NT) and HT conditions, using paired well-watered (WW) and MD strategies during anthesis, in both controlled-climate pot and open-air field conditions over multiple years. Compared to the conventional WW regime under HT stress, which significantly reduced JAs levels in lodicules and worsened spikelet opening impairment and hybrid seed yield loss, the MD treatment demonstrated significant protective effects. The MD regime enhanced JAs accumulation in lodicules, effectively alleviating HT-induced spikelet opening impairment and hybrid seed yield reduction. This protective mechanism operates through multiple pathways: (1) promoting starch hydrolysis into soluble sugars, (2) upregulating the expression of aquaporin genes, and (3) enhancing antioxidant capacity, thereby maintaining cellular osmotic and redox homeostasis in lodicules. The crucial role of JAs in this mechanism was confirmed using JA-deficient mutants, transgenic rice lines with varying JA biosynthesis capacities, and exogenous JAs applications. These findings indicate that MD is a more effective cultivation strategy than traditional WW in protecting PTGMS rice from HT stress, achieved by modulating JAs levels to maintain osmotic and redox homeostasis in lodicules, thus improving spikelet opening and hybrid seed yield under HT stress during anthesis.