Genome-wide identification of HSF family in tree peony reveals the function of PsHSFA3 in response to thermal stress.

High temperature stress severely constrains the growth and cultivation of tree peony (Paeonia suffruticosa), restricting its widespread application in the Jiangnan region of China. The traditional cultivar 'Hu Hong' displays strong thermal tolerance and ornamental value, making it an ideal model for investigating molecular mechanisms of heat resistance. Previous transcriptomic analyses suggested that the HSF family plays a critical role in enhancing heat resistance in tree peony. In this study, we conducted genome-wide identification, bioinformatic analysis, and functional characterization of PsHSFA3 in relation to heat tolerance in the tree peony HSF gene family. A total of nineteen HSF family members were identified. Promoter analysis revealed the presence of multiple cis-acting elements and predicted binding sites for thirteen transcription factor families. Based on expression profiling, PsHSFA3 was selected as a central candidate gene for further investigation. Subcellular localization indicated that PsHSFA3 is nuclear-localized, and expression analysis showed preferential accumulation in leaves, with strong induction under heat stress. Functional studies demonstrated that PsHSFA3 contributes to thermotolerance by modulating osmotic adjustment capacity and antioxidant enzyme activities. Furthermore, yeast one-hybrid assays indicated that PsDREB2A directly binds to the promoter of PsHSFA3. These findings provide important insights into the regulatory mechanisms underlying heat stress response in tree peony and offer a theoretical foundation for breeding heat-resistant varieties.