Regulated expression of the Transcription Factor HYR in Rice Improves Grain Yield and Grain Quality under Drought and High-Temperature Stress Conditions

The photosynthetic activity of the rice plants that directly correlated with the grain yield needs to be increased in order to meet the global food demand. Climate change triggers environmental stresses, including drought and high-temperature stress, which negatively affect photosynthesis and limits grain yield. The HYR (Higher Yield Rice) transcription factor gene regulates rice's photosynthetic carbon metabolism (PCM). Overexpression of HYR (Os03g02650) in rice lines enhances photosynthetic capacity and contributes to higher grain yield under normal conditions and drought and high-temperature stress conditions. Since HYR is involved in regulating PCM and response to environmental stress signals, we were interested in studying the genetic basis of this response. The results show that expression of HYR was strongly affected by circadian rhythm. Our results suggest how the circadian system may be an essential target for optimizing PCM and yield under drought and high-temperature stress. In this study, HYR lines of IR-64 HYR and Vandana HYR showed higher filled grain per panicle number under normal and environmental stress conditions than WT. Most of the HYR lines produced higher filled grain per panicle number under control and environmental stress conditions with longer, wider, heavier, and less chalkiness than WT. Alteration of the root anatomy components of the HYR lines, increasing in metaxylem number and aerenchyma area, and also decreasing in metaxylem size and cortical cell file number under normal and environmental stress conditions showed a significant positive correlation with grain yield and grain quality characteristics.