Overexpression of StHsfA2 Enhances Thermotolerance and Promotes Tuberisation in Potato Under High Temperature Through StSP6A

ABSTRACT High temperature (HT) is a major environmental stress that severely inhibits potato ( Solanum tuberosum L.) tuberisation and yield. Heat shock transcription factors (Hsfs) are pivotal in plant thermotolerance, yet their roles in potato remain unclear. Here, we demonstrate that overexpression of StHsfA2 , a rapidly HT–responsive HSF family member, enhances thermotolerance and mitigates yield loss in transgenic potato under HT conditions. We reveal that StHsfA2 upregulates StSP6A expression by binding to the heat shock element–like motifs in its promoter. StSP6A encodes a homologue of FLOWERING LOCUS T that is critical for initiating tuber formation. Intriguingly, we found that StHsfA2 physically interacts with the StSP6A protein, which in turn inhibits StHsfA2–mediated StSP6A upregulation. However, HT stress attenuates the StHsfA2–StSP6A interaction. Thus, a negative feedback loop modulates StSP6A regulation by StHsfA2 under HT. In summary, our study shows that StHsfA2 is a key regulator of thermotolerance in potato plants. Its overexpression enhances heat resistance and could boost tuber yield, making it a promising candidate gene for countering yield loss amid global warming.