Comprehensive Genome-Wide Analysis and Expression Profiling of the Heat Shock Transcription Factor (Hsf) Gene Family, and Function Detection of BpHsf11 in Heat Stress Response in Paper Mulberry (Broussonetia papyrifera)

High temperatures pose a significant threat to plant growth and survival. Heat shock factors (Hsfs) regulate heat shock proteins (Hsps) and stress-related genes. This study examines the Hsf gene family and the role of BpHsf11 in heat tolerance in Broussonetia papyrifera (L.) L'Hér. ex Vent. Twenty BpHsfs were identified through genome-wide analysis. Phylogenetic classification, conserved motif identification, and promoter cis-element analysis were performed. Subcellular localization was used to determine the location of BpHsf11 protein. Expression patterns under heat stress (42°C) were analyzed via RNA-seq and qRT-PCR. BpHsf11 was functionally validated in yeast. In the genome of B. papyrifera, 20 BpHsf genes have been identified and categorized into three primary groups (A, B, C) according to their protein structure and phylogenetic features. Unon analyzing the promoter region of BpHsfs, several stress-related regulatory elements were found. Synteny analysis revealed a substantial presence of syntenic gene pairs between the B. papyrifera Hsf gene family and those of Arabidopsis thalianas and Populus, with two instances of segmental duplication observed among the BpHsf genes. Under heat stress, the expression of seven BpHsf members changed significantly. Their expression levels increased initially, peaked at 12 h, and then decreased. Subcellular localization revealed BpHsf11 protein localized to the cytoplasmic membrane and nucleus. Yeast validation of BpHsf11 demonstrated growth inhibition in both experimental and control groups following 2-h incubation at 50°C, although the yeast expressing BpHsf11 showed a lesser degree of suppression compared to the control group. Certain members of the BpHsf family exhibit notable alterations in expression levels when exposed to elevated temperatures. Specifically, BpHsf11 has been shown to enhance yeast thermotolerance in response to heat stress, suggesting its potential to enhance stress resistance in mulberry trees.