ATP utilization efficiency plays a key role in determining rice quality under high-temperature conditions

High-temperature stress significantly adversely affects both rice yield and quality by disrupting energy metabolism, specifically ATP levels and ATP utilization efficiency. However, the exact mechanisms involved remain unclear. This study investigated two rice cultivars with distinct heat tolerance: ZZY1, which produces a higher yield but lower quality, and ZZY8, which has a lower yield but higher quality. Both cultivars were subjected to heat stress during the flowering stage. As temperatures increased, both cultivars experienced considerable declines in grain yield, seed-setting rate, and kernel weight, with ZZY8 showing more severe impacts. Furthermore, ZZY1 demonstrated a significant rise in chalkiness and a reduction in the head rice rate. To uncover the underlying mechanisms, the study analyzed antioxidant enzyme activity, levels of H₂O₂ and MDA, and various factors related to energy metabolism, including ATP content, ATPase levels, energy charge, AOX content, and the activity of complexes I and V, alongside NAD(H) and NADP(H) content, as well as transcriptome analysis. The complex V content was increased in ZZY1 while decreased in ZZY8, as well as the ATPase decreased more in ZZY1 than ZZY8, which illustrated the ZZY8 had a higher ATP utilization efficiency. The findings showed that ZZY1 had a notably higher ATP content than ZZY8, while ZZY8 exhibited elevated ATPase levels. Transcriptome analysis supported these observations, suggesting that ATP utilization efficiency may be crucial in determining rice quality under high-temperature stress during flowering stage.