Genome-Wide Characterisation of the Heat Shock Transcription Factor Gene Family in Betula platyphylla Reveals Promising Candidates for Heat Tolerance

Heat stress transcription factors (HSFs) play a critical role in orchestrating cellular responses to elevated temperatures and various stress conditions. While extensively studied in model plants, the HSF gene family in Betula platyphylla remains unexplored, despite the availability of its sequenced genome. In this study, we employed bioinformatics approaches to identify 21 BpHSF genes within the B. platyphylla genome, revealing their uneven distribution across chromosomes. These genes were categorized into three subfamilies: A, B, and C. Each characterized by conserved protein motifs and gene structures, with notable divergence observed between subfamilies. Collinearity analysis suggested that segmental duplication events have driven the evolutionary expansion of the BpHSF gene family. Promoter region analysis identified an array of cis-acting elements linked to growth, development, hormonal regulation, and stress responses. Subcellular localization experiments confirmed the nuclear localization of BpHSFA2a, BpHSFB1a, and BpHSFC1a, consistent with in silico predictions. RNA-seq and RT-qPCR analyses revealed tissue-specific expression patterns of BpHSF genes and their dynamic responses to heat stress, with qPCR validation highlighting a significant upregulation of BpHSFA2a under high-temperature conditions. In summary, this study provided a comprehensive characterization of the HSF gene family in B. platyphylla, laying a solid foundation for future functional studies. Particularly, BpHSFA2a emerges as a promising candidate gene for enhancing heat tolerance in B. platyphylla, warranting further detailed investigation.