Identification of HSF gene family and functional analysis of two HSFA1 genes with tandem repeat features in Fritillaria cirrhosa D.Don

BACKGROUND: Heat stress (HS) is a growing environmental factor impacting the growth and medicinal value of plateau medicinal plants due to global climate change. Plant heat shock factors (HSFs) are key transcriptional regulators in HS responses, yet the mechanisms of HSFs in plateau medicinal plants remain largely unexplored. RESULTS: In this study, we identified 17 HSF genes from the plateau medicinal plant Fritillaria cirrhosa D.Don. All FcHSF members were divided into two different phylogenetic groups. Moreover, the distribution of conserved motifs among these genes reveals subfamily-specific divergence. PCR-based cloning was further used to amplify two transcript variants of FcHSFA1, designated as FcHSFA1a and FcHSFA1b, which display distinct tandem repeat configurations at their C-termini regions. Both variants were upregulated under HS, with FcHSFA1b showing higher expression. Subcellular localization showed both variants in the nucleus and cytoplasm of tobacco epidermal cells. FcHSFA1b exhibited stronger transcriptional activation activity than FcHSFA1a in yeast cells. Overexpression of both variants in tobacco enhanced HS-related gene expression, increased peroxidase activity and chlorophyll content, and thereby improved thermotolerance. CONCLUSIONS: These findings suggest that FcHSFA1 variants contribute to heat tolerance, with distinct transcriptional responses, offering strategies to enhance basal thermotolerance in F. cirrhosa.