Identification and Tissue-Specific Expression Analysis of CYP720B Subfamily Genes in Slash Pine and Loblolly Pine

Diterpene resin acids (DRAs) are major components of pine oleoresin that can effectively resist the invasion of insects and pathogenic microorganisms. The subfamily of cytochrome P450s, CYP720B, catalyzes diterpene products into DRAs. Identifying CYP720B subfamily members and revealing the characteristics of tissue-specific expression would help understand diterpene-rich structures and diverse types. Slash pine and loblolly pine are important pines that provide oleoresin products. In this study, we identified CYP720B candidate genes based on the Pinus taeda V2.0 genome and full-length transcriptome of slash pine by PacBio. A total of 17 genes in slash pine and 19 in loblolly pine were identified and classified into four main clades by phylogenetic analysis. An analysis of cis-acting elements showed that CYP720B genes were closely related to adversity resistance. The gene expression of these candidates in different tissues was quantified by real-time quantitative PCR (RT-qPCR) analysis. Most of the genes showed relatively higher expression levels in roots and stems than in the other tissues, corresponding with the results of DRA component detection by gas chromatography-mass spectrometry (GC-MS), which indicated that stems and roots might be important tissues in oleoresin biosynthesis. These results provide a valuable resource for a better understanding of the biological role of individual CYP720Bs in slash pine and loblolly pine.