Transcriptional regulation modulates terpenoid biosynthesis of Pinus elliottii under drought stress

Global climate change has increased the frequency and severity of droughts, which may affect the biosynthesis of coniferous terpenes, but the regulatory mechanism is still unclear. We explored the mechanisms of terpenoid regulation in response to drought stress by resolving changes in terpenoid composition and gene expression under drought stress to better understand the expression profile of terpenoid synthesis in slash pine. We obtained three main results: (1) A total of 1393 differentially expressed genes (DEGs) were identified, mainly including MYB, AP2/ERF, WRKY and other transcription factors, which were reported to be associated with plant resistance. Real-time quantitative PCR (RT-qPCR) verified the reliability of transcriptomic data, and the analysis of its results shows a close correlation with the data obtained by RNA-seq. (2) A total of 39 DEGs encoding 7 types of the proteins that were identified in the terpene synthesis pathway; what's more, TPS (e.g., PITA_24906, PITA_00655, PITA_09277) and CYP720B11 (PITA_22711) showed high expressions in diterpene synthesis. (3) A weighted coexpression network analysis (WGCNA) showed high correlations between levopimaric acid content and module genes expression. Network visualization of the 70 hub genes revealed this high degree of connectivity between PITA_24906 and other genes, suggesting that PITA_24906 might play a regulatory role in levopimaric acid under drought stress. Thus, the results of this study will lead to a better understanding of the defense mechanisms of slash pine and provide a basic reference for the management and genetic improvement of slash pine stands.