Genome-Wide Identification of the HSF Genes in Sweet Potato and Functional Role of IbHSF22 in Anthocyanin Accumulation and Salt Stress Tolerance

Heat shock transcription factors (HSFs) play a central role in mediating plant responses to abiotic stress. Anthocyanins, one of the most important secondary metabolites in plants, contribute to both stress tolerance and the enhancement in crop nutritional quality. However, the possible role of HSFs in regulating anthocyanin biosynthesis in sweet potato (<i>Ipomoea batatas</i> L.) remains unknown. This study conducted a genome-wide analysis of the sweet potato HSF gene family to explore their functions related to anthocyanin metabolism and salinity stress. Multiple stress-inducible promoter elements were identified within <i>IbHSF22</i>, including those induced by drought, salt, heat, ABA, and light. For functional characterization of this gene, a 35S-driven overexpression construct was prepared and then transformed into <i>Nicotiana benthamiana</i>. Overexpression of <i>IbHSF22</i> led to a nearly two-fold increase in anthocyanin content, concurrently with the elevated expression of key structural genes such as <i>NtCHS</i>, <i>NtF3H</i>, <i>NtDFR</i>, and <i>NtANS</i>. Under salt stress, the transgenic plants also exhibited enhanced tolerance, which was associated with maintained antioxidant enzyme activity and concerted induction of stress-responsive genes, events that collectively resulted in decreased oxidative damage. Therefore, the present work identifies <i>IbHSF22</i> as an integrator of anthocyanin biosynthesis and salt defense mechanisms. These findings provide a conceptual basis and candidate gene strategy for dual improvement in stress resilience and nutritional quality in sweet potato breeding.