Genome-Wide Identification of HSP70 Gene Family and Their Roles in the Hybrid Tea Rose Heat Stress Response

Hybrid tea roses (Rosa hybrida) are economically important horticultural crops and highly susceptible to heat stress, which significantly impacts flower quality and yield. As a key member of the heat shock protein (HSP) family, HSP70 protein acts as a molecular chaperone and exhibits diverse abiotic stress response functions in plants. A total of 113 HSP70 transcription factors (TFs) with varying physical and chemical properties were identified in the genome of hybrid tea rose. Phylogenetic analysis showed that the identified TFs could classify into three (I, II, and III) subfamilies, with most members (51 TFs) falling in subfamily II. Wide gene structural variations were observed among the three subfamilies, with group I and II members lacking introns, while group III members only harbored 1~4 exons and introns. Numerous cis-acting elements associated with abiotic stress, hormone response, growth and development responses, as well as light response were detected in the HSP70 gene promoters. In addition, protein interaction networks predicted a wide range of interactions between different hybrid tea rose HSP70 subfamilies. Gene expression analysis revealed that 57 HSP70 genes had strong organ specificity and response to heat stress in the hybrid tea rose plants. Notably, the expression levels of two RhHSP70 genes, RhHSP70-69 and RhHSP70-88, were significantly increased after heat stress, indicating that these two genes might be crucial for plant heat stress response. Subcellular localization of RhHSP70-69 and RhHSP70-88 revealed that their proteins were located in the nucleus. Our results are not only useful for future evaluation of the regulatory roles of RhHSP70 genes in the hybrid tea rose growth and development, but also provides key genes for future molecular breeding of heat tolerant plants.