Transcriptomic and Functional Characterization of ClHsf8 Reveals Key Mechanisms of Heat Stress Response in...

Cunninghamia lanceolata (C. lanceolata), a pivotal economic timber species in southern China, faces increasing threats from global warming and heat stress. Due to limited knowledge regarding its stress response mechanisms, uncovering the molecular basis of heat tolerance is crucial for breeding resilient varieties. Therefore, the objective of this study was to elucidate the physiological and molecular mechanisms of C. lanceolata in response to heat stress. In this study, we performed a time-series transcriptomic analysis on leaves of C. lanceolata '6421' seedlings exposed to heat stress (39 °C) for 0, 1, 4, 8, 12, and 16 h. A total of 1130 differentially expressed genes (DEGs) were identified, with functions primarily enriched in signal transduction, protein folding, and the MAPK and NF-kappa B signaling pathways. Weighted gene co-expression network analysis (WGCNA) revealed a complex regulatory network, identifying ClHsf8 as a central hub transcription factor. To validate its function, ClHsf8 was cloned and overexpressed in tobacco (Nicotiana benthamiana). Under heat stress conditions, transgenic plants exhibited enhanced thermotolerance compared to wild-type controls, characterized by significantly higher activities of antioxidant enzymes (SOD, POD, and CAT) and reduced accumulation of MDA and H₂O₂. Our findings elucidate the molecular regulatory mechanisms of C. lanceolata in response to high temperatures and demonstrate the functional role of ClHsf8 in conferring heat tolerance, providing a theoretical foundation for the genetic improvement of heat-resilient cultivars.