Identification of genes involved in oleoresin biosynthesis in Pinus massoniana through the combination of SMRT and Illumina sequencing

Abstract

Oleoresin, a terpene with important economic and industrial value, is produced via the secondary metabolism of plants in the genus Pinus. Owing to its adaptability and high economic and ecological value, Pinus massoniana (Masson pine) is widely planted in southern China, and this species is also the main species for oleoresin tapping in the world. However, the differences in the expression of genes related to terpene biosynthesis in needles and xylem tissues at the transcriptional level at different time points during oleoresin tapping are still unclear. By combining SMRT and Illumina sequencing, we revealed the key genes involved in terpene biosynthesis in needles and xylem tissues. A total of 32.07 Gb of polymerase reads and 562.60 Gb of Illumina clean reads were obtained in this study. After annotating them in seven databases, we identified 68 genes involved in terpene biosynthesis, and most of them were highly expressed in needles, implying that needles are the biosynthetic sites of oleoresin. Moreover, we found that the TPS genes of gymnosperms more likely to be ‘DDXYD’, compared to the ‘DDXXD’ motif in angiosperms. The genes involved in the MEP pathway are highly expressed in the needles, implying the different efficiency of use of the MEP and MVA pathways in Masson pine. Furthermore, by performing controlled experiments, we found that PmPMK2, PmHDR1, PmTPS09, PmTPS11, PmTPS16, and PmTPS19 genes may play a critical role in oleoresin biosynthesis. This study provide new insights into terpene and oleoresin biosynthesis.