PtHSF5, a HSF transcription factor from Pinellia Ternata positively regulates heat tolerance in Arabidopsis

Pinellia ternata (Thunb.) Breit., a traditional Chinese medicinal herb, frequently experiences ‘sprout tumble’ under heat stress during growth, significantly compromising its yield potential. While heat shock transcription factors (HSFs) are known to play critical roles in plant thermotolerance regulation, the functional characterization of HSFs in P. ternata remains unexplored. In this study, we identified a heat-inducible PtHSF5 that exhibits tissue-specific expression dominance in petioles and leaves. Subcellular localization analysis revealed nuclear confinement of PtHSF5, which notably lacks intrinsic transcriptional activation capability. Transgenic Arabidopsis overexpressing PtHSF5 demonstrated enhanced seed germination rates, primary root elongation, and seedling survival under thermal stress, indicating its positive regulatory role in thermotolerance. Mechanistic investigations revealed that PtHSF5 overexpression significantly increased enzymatic activities of key antioxidant enzymes - peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) - while effectively reducing reactive oxygen species (ROS) accumulation under heat stress. Transcriptome profiling further demonstrated PtHSF5-mediated regulation of phenylpropanoid biosynthesis pathway genes, suggesting its potential role in enhancing ROS scavenging capacity through modulation of this metabolic pathway, thereby improving heat stress adaptation. This study provides novel insights into the molecular mechanisms underlying heat stress adaptation in P. ternata and establishes PtHSF5 as a promising candidate for improving thermotolerance in medicinal plants.