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

This study investigated the role of jasmonates (JAs) in mitigating the impairment of high temperature (HT) stress-induced spikelet opening 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, paired with either well-watered (WW) or MD strategies during anthesis, in both controlled-climate pot and open-air field conditions over multiple years. The MD treatment demonstrated significant protective effects compared to the conventional WW regime under HT stress, which significantly reduced the levels of JAs in lodicules and worsened spikelet opening impairment and hybrid seed yield loss. The MD regime enhanced the accumulation of JAs 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 the lodicules. The crucial role of JAs in this mechanism was confirmed using JA-deficient mutants, transgenic rice lines with varying JA biosynthetic capacities, and exogenous applications of JAs. These findings indicate that MD is a more effective cultivation strategy than traditional WW in protecting PTGMS rice from HT stress, which is achieved by modulating levels of JAs to maintain osmotic and redox homeostasis in the lodicules, thus improving spikelet opening and hybrid seed yield under HT stress during anthesis.