Characterization and Functional Analysis of RhHsfA7, a Heat Stress Transcription Factor in Roses (Rosa hybrid ‘Samantha’)

Heat stress transcription factors (Hsfs) are crucial transcription factors (TFs) in plants, playing pivotal roles in responding to abiotic stresses. However, their specific functions in regulating heat stress responses in roses are not yet fully elucidated. Here, we cloned an Hsf gene, RhHsfA7, from the rose variety Rosa hybrid ‘Samantha’. This gene contains a coding sequence (CDS) of 1086 bp, encoding 361 amino acids. The RhHsfA7 protein has a molecular weight of 41.21 kDa, an isoelectric point of 5.41, and no signal peptide or transmembrane structure. Phylogenetic analyses revealed that RhHsfA7 is most closely related to AtHsfA7a, AtHsfA7b, and AtHsfA6b in Arabidopsis thaliana, and is phylogenetically closer to Rosaceae species compared to other species. The RhHsfA7 protein possesses conserved domains, including an oligomerization domain (OD), a nuclear localization signal (NLS), a DNA-binding domain (DBD), and a nuclear export signal (NES), as well as the HsfA subfamily-specific transcriptional activation domain (AHA). RhHsfA7 was localized in the nucleus and exhibited transcriptional activation activity. Expression analysis revealed that RhHsfA7 was highly expressed in roots and leaves, and its expression was heat-specific. In rose leaves, through silencing and transient overexpression experiments, we discovered that silencing RhHsfA7 resulted in heat sensitivity, whereas transient overexpression of RhHsfA7 increased heat tolerance. Collectively, our findings suggest that RhHsfA7 positively regulates tolerance to heat stress in roses.