ABSTRACT
Pinaceae is the largest family of conifers, dominating forest ecosystems and serving as the backbone of northern, temperate and mountain forests. The terpenoid metabolism of conifers is responsive to pests, diseases, and environmental stress. Determining the phylogeny and evolution of terpene synthase genes in Pinaceae may shed light on early adaptive evolution. We used different inference methods and datasets to reconstruct the Pinaceae phylogeny based on our assembled transcriptomes. We identified the final species tree of Pinaceae by comparing and summarizing different phylogenetic trees. The genes encoding terpene synthase (TPS) and cytochrome P450 proteins in Pinaceae showed a trend of expansion compared with those in Cycas. Gene family analysis revealed that the number of TPS genes decreased while the number of P450 genes increased in loblolly pine. Expression profiles showed that TPSs and P450s were mainly expressed in leaf buds and needles, which may be the result of long-term evolution to protect these two vulnerable tissues. Our research provides insights into the phylogeny and evolution of terpene synthase genes in Pinaceae and offers some useful references for the investigation of terpenoids in conifers.
ABSTRACT
Loblolly pine (Pinus taeda L.) is an important tree for afforestation with substantial economic and ecological value. Many metabolites with pharmacological activities are present in the tissues of P. taeda. However, the biosynthesis regulatory mechanisms of these metabolites are poorly understood. In the present study, transcriptome and metabolome analyses were performed on five tissues of P. taeda. A total of 40.4 million clean reads were obtained and assembled into 108,663 unigenes. These were compared with five databases, revealing 39,576 annotated unigenes. A total of 13,491 differentially expressed genes (DEGs) were observed in 10 comparison groups. Of these, 487 unigenes exhibited significantly different expressions in specific tissues of P. taeda. The DEGs were explored using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes metabolic pathway analysis. We identified 343 and 173 candidate unigenes related to the biosynthesis of terpenoids and flavonoids, respectively. These included 62 R2R3-MYB, 30 MYB, 15 WRKY, seven bHLH, seven ERF, six ZIP, five AP2, and one WD40 genes that acted as regulators in flavonoid and/or terpenoid biosynthesis. Additionally, metabolomics analysis detected 528 metabolites, among which 168 were flavonoids. A total of 493 differentially accumulated metabolites (DAMs) were obtained in 10 comparison groups. The 3,7-Di-O-methyl quercetin was differentially accumulated in all the comparison groups. The combined transcriptome and metabolome analyses revealed 219 DEGs that were significantly correlated with 45 DAMs. Our study provides valuable genomic and metabolome information for understanding P. taeda at the molecular level, providing a foundation for the further development of P. taeda-related pharmaceutical industry.
