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

## TL;DR

This study identifies and analyzes heat shock transcription factors in kelp, revealing their roles in stress responses and gene regulation.

## Contribution

The first comprehensive characterization of HSFs in brown algae, including their phylogeny, expression, and regulatory motifs.

## Key findings

- Sixteen SjHSFs were identified in Saccharina japonica, forming a distinct evolutionary clade.
- SjHSF-03 recognizes seven conserved motifs, including in promoters of 23 HSP genes upregulated under heat stress.
- Tissue-specific and stress-induced expression patterns highlight the functional diversity of SjHSFs.

## Abstract

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 Saccharina japonica. A total of sixteen SjHSFs were identified. Phylogenetic analysis revealed that HSFs from brown algae form a distinct clade, separate from those from red algae, green algae, moss, and Arabidopsis thaliana. The DNA-binding domain was found to be highly conserved among SjHSFs. Analysis of cis-acting elements in SjHSF promoters suggested their potential roles in regulating growth, development, and stress responses. Tissue-specific expression profiles revealed differential expression of SjHSFs across various tissues of S. japonica. Under abiotic stresses, certain SjHSFs 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 S. japonica genes involved in diverse biological processes and pathways. Notably, 23 heat shock protein (HSP) genes were among these motif-containing genes, and 21 out of these 23 SjHSPs 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 S. japonica and other brown algae.