Cunninghamia lanceolata (Lamb.) Hook. (Chinese fir) is an important timber species that is widely cultivated in southern China. However, the shallow root system and weak drought resistance of Chinese fir are not enough to cope with high temperature and drought. In recent years, molecular biology has been used to modify plants to make them more resilient. Therefore, improving heat and drought resistance of Chinese fir by molecular biology technology is one of the best choices, whereas fewer genetic information resources for C. lanceolata limit more comprehensive molecular studies. In this study, single-molecule full-length transcriptome (SMRT) sequencing technology was used to obtain full-length transcriptome data on Chinese fir. A total of 21,331 transcripts were obtained via co-assembly, and 11,094 gene sets were obtained via further de-redundancy. In addition, gene function annotation and gene structure analysis were performed. We also used these data to identify nine heat shock transcription factors (Hsfs) in Chinese fir, and heat stress transcriptome and real-time quantitative polymerase chain reaction (PCR) analyses revealed expression changes in response to heat stress, indicating that these may play roles in heat resistance. These studies have enriched the genetic information resources of Chinese fir, which may be utilized for further species promotion, improvement, and application.

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.