Genome-Wide Characterization of the HSF Gene Family in Paulownia fortunei and Preliminary Functional Analysis of PfHSF6 in Drought Response

This is the authors' abstract. We don't add key points for this paper.

Heat shock transcription factors (HSFs) act as crucial regulatory components in plant stress regulatory network and play essential roles in abiotic stress adaptation, particularly drought tolerance. Here, we identified 36 PfHSF gene family members in Paulownia fortunei through genome-wide analysis. Their chromosomal distribution, physicochemical properties, phylogenetic relationships, gene structures, conserved motifs, cis-acting elements, and post-translational modification sites were systematically characterized. Transcriptome-based expression profiling demonstrated distinct tissue-specific and drought-responsive expression patterns among PfHSF members, with PfHSF6 being strongly up-regulated under drought. Subcellular localization assays confirmed nuclear and plasma membrane localization of PfHSF6. Transient overexpression of PfHSF6 in tobacco significantly enhanced drought tolerance, as evidenced by alleviated wilting, a ~60% reduction in MDA content, ~2-fold increases in SOD and POD activities, and a ~67% reduction in electrolyte leakage relative to the control (p < 0.01); consistently, stress-responsive genes such as NbRD29A and NbLEA5 were up-regulated by ~6- and ~3-fold, respectively. This study provides a comprehensive characterization of the PfHSF family and preliminary functional evidence for PfHSF6, offering candidate genes for further functional validation and potential drought-tolerance breeding in paulownia.