Genome-Wide Analysis of Heat Shock Transcription Factors (HSFs) in Kelp (Saccharina japonica) and Analysis of Their Expression in Response to Abiotic Stresses

Heat shock transcription factors (HSFs) play a crucial role in mediating responses to abiotic stresses. However, characterization of HSFs in macroalgae remains largely unexplored. In this study, a comprehensive analysis of HSFs was carried out in <i>Saccharina japonica</i>. A total of sixteen <i>SjHSFs</i> were identified. Phylogenetic analysis revealed that HSFs from brown algae form a distinct clade, separate from those from red algae, green algae, moss, and <i>Arabidopsis thaliana</i>. The DNA-binding domain was found to be highly conserved among SjHSFs. Analysis of cis-acting elements in <i>SjHSF</i> promoters suggested their potential roles in regulating growth, development, and stress responses. Tissue-specific expression profiles revealed differential expression of <i>SjHSFs</i> across various tissues of <i>S. japonica</i>. Under abiotic stresses, certain <i>SjHSFs</i> exhibited dynamic expression patterns, with particularly pronounced changes observed under high-temperature stress. We further employed a transcription factor-centered yeast one-hybrid (TF-Centered Y1H) to determine the motifs recognized by SjHSF-03. Seven conserved motifs were identified, and the distributions of these motifs were screened in the promoter regions of <i>S. japonica</i> genes involved in diverse biological processes and pathways. Notably, 23 heat shock protein (<i>HSP</i>) genes were among these motif-containing genes, and 21 out of these 23 <i>SjHSPs</i> were up-regulated under heat stress. Our results provide a solid foundation for future research on the specific functions of HSFs under different stress conditions and the regulatory mechanisms of HSF-mediated stress responses in <i>S. japonica</i> and other brown algae.