Identification, expression, and phylogenetic analyses of terpenoid biosynthesis-related genes in secondary xylem of loblolly pine (Pinus taeda L.) based on transcriptome analyses

SMRT and Illumina sequencing provide insights into mechanisms of lignin and terpenoids biosynthesis in Pinus massoniana Lamb

Wood and oleoresin are important industrial raw materials with high economic value; however, their molecular formation and biosynthesis mechanisms in different tissues of Pinus massoniana remain unexplored. Therefore, we used single-molecule real-time sequencing technology (SMRT) and Illumina RNA sequencing to establish a transcriptome dataset and explore the expression pattern of genes related to secondary metabolites involved in wood formation and oleoresin biosynthesis in six different P. massoniana tissues. In total, 63.58 Gb of polymerase reads were obtained, including 41,407 isoforms with an average length of 1822 bp. We identified 3939 and 8785 isoforms and 161 and 481 transcription factors with tissue expression specificity and in the reproductive and vegetative organs, respectively. Eighty isoforms were annotated as cellulose synthases and 224 isoforms involved in lignin biosynthesis were enriched. Additionally, we identified 217 isoforms involved in the terpenoid biosynthesis pathway, with needles having the most tissue-specific genes for terpenoid biosynthesis. Some isoforms related to lignin biosynthesis were highly expressed in the xylem, according to the results of transcriptome sequencing and real-time quantitative reverse-transcription polymerase chain reaction. Our research confirmed the advantages of SMRT sequencing and provided valuable information for the transcriptional annotation of P. massoniana, which will be beneficial for producing better raw wood and oleoresin materials.

Phylotranscriptomics and evolution of key genes for terpene biosynthesis in Pinaceae

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.

Genome structure and evolutionary history of frankincense producing Boswellia sacra

Boswellia sacra Flueck (family Burseraceae) tree is wounded to produce frankincense. We report its de novo assembled genome (667.8 Mb) comprising 18,564 high-confidence protein-encoding genes. Comparing conserved single-copy genes across eudicots suggest >97% gene space assembly of B. sacra genome. Evolutionary history shows B. sacra gene-duplications derived from recent paralogous events and retained from ancient hexaploidy shared with other eudicots. The genome indicated a major expansion of Gypsy retroelements in last 2 million years. The B. sacra genetic diversity showed four clades intermixed with a primary genotype—dominating most resin-productive trees. Further, the stem transcriptome revealed that wounding concurrently activates phytohormones signaling, cell wall fortification, and resin terpenoid biosynthesis pathways leading to the synthesis of boswellic acid—a key chemotaxonomic marker of Boswellia. The sequence datasets reported here will serve as a foundation to investigate the genetic determinants of frankincense and other resin-producing species in Burseraceae.

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Assembly and architecture of frankincense producing Boswellia sacra Flueck

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Comparative genomics and evolutionary history of frankincense tree within orders

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Transcriptome of stem part and gene expression patterns of wounding to the tree

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Resin biosynthesis pathway and related CYP450 enzymes and gene families

Morphological and Comparative Transcriptome Analysis of Three Species of Five-Needle Pines: Insights Into Phenotypic Evolution and Phylogeny

Pinus koraiensis, Pinus sibirica, and Pinus pumila are the major five-needle pines in northeast China, with substantial economic and ecological values. The phenotypic variation, environmental adaptability and evolutionary relationships of these three five-needle pines remain largely undecided. It is therefore important to study their genetic differentiation and evolutionary history. To obtain more genetic information, the needle transcriptomes of the three five-needle pines were sequenced and assembled. To explore the relationship of sequence information and adaptation to a high mountain environment, data on needle morphological traits [needle length (NL), needle width (NW), needle thickness (NT), and fascicle width (FW)] and 19 climatic variables describing the patterns and intensity of temperature and precipitation at six natural populations were recorded. Geographic coordinates of altitude, latitude, and longitude were also obtained. The needle morphological data was combined with transcriptome information, location, and climate data, for a comparative analysis of the three five-needle pines. We found significant differences for needle traits among the populations of the three five-needle pine species. Transcriptome analysis showed that the phenotypic variation and environmental adaptation of the needles of P. koraiensis, P. sibirica, and P. pumila were related to photosynthesis, respiration, and metabolites. Analysis of orthologs from 11 Pinus species indicated a closer genetic relationship between P. koraiensis and P. sibirica compared to P. pumila. Our study lays a foundation for genetic improvement of these five-needle pines and provides insights into the adaptation and evolution of Pinus species.

Transcriptome analysis reveals important candidate gene families related to oligosaccharides biosynthesis in Morindaofficinalis

Morinda officinalis How (MO) is one of the best-known traditional herbs and is widely cultivated in subtropical and tropical areas for many years, especially in southern China. Oligosaccharides are the major constituents in the roots of MO, which is well known for its therapeutic effects with anti-depression, anti-osteoporosis, memory-enhancing, ect. To date, the main gene families that regulate the biosynthetic pathway of MO oligosaccharides metabolism yet have been published. In our study, six cDNA libraries generated from six plants of MO were sequenced utilizing an Illumina HiSeq 4000 platform. Corresponding totals of more than 132.60 million clean reads were obtained from the six libraries and assembled into 25,812 unigenes with an average length of 1288 bp. Moreover, 6036 unigenes were found to be allocated to 26 pathways maps using several public databases, and 2538 differential expression genes (DEGs) were screened. Among them, 25 genes from three families were selected as the mainly candidate genes related to MO oligosaccharides biosynthesis. Then, the expression patterns of six DEGs closely related to MO oligosaccharides biosynthesis were verified by quantitative real-time PCR (qRT-PCR). Besides, the MO was clustered more closely to Coffea arabica of Rubiaceae. In summary, the transcriptomic analysis was used to investigate the differences in expression genes of oligosaccharides biosynthesis, with the notable outcome that several key gene families were closely linked to oligosaccharides biosynthesis.

Impact of potential stimulants on asiaticoside and madecassoside levels and expression of triterpenoid-related genes in axenic shoot cultures of Centella asiatica (L.) Urb

The triterpenoid saponins, asiaticoside and madecassoside from Centella asiatica (L.) Urb. are known to have a wide range of applications in pharmaceutical and cosmetic industries. The effect of addition of Potential Metabolite Stimulants (PMSs) - casein acid hydrolysate, meat peptone, salicylic acid, copper sulphate, and silver nitrate, on the concentrations of these saponins and transcript levels of associated genes encoding important biosynthetic enzymes, was assessed in axenic shoot cultures of C. asiatica. Among the stimulants, silver nitrate induced asiaticoside content approximately 6-fold increase in madecassoside levels, after three weeks post-treatment with a decrease in biomass compared to its control. Gene expression analysis of essential genes involved in triterpenoid synthesis such as β-amyrin synthase showed an upregulation of approximately 50-fold at the third week of silver nitrate treatment compared to control. These findings suggest that silver nitrate can act as a metabolite stimulant, to enhance the formation of triterpenoids in axenic shoot culture of C. asiatica, which could be utilized in studying the regulation of terpenoid biosynthesis and biotechnological application for the increased production of these bioactive molecules.

Integrated Analysis of the Transcriptome and Metabolome Reveals Genes Involved in Terpenoid and Flavonoid Biosynthesis in the Loblolly Pine (Pinus taeda L.)

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.

…Fell Upas Sits, the Hydra-Tree of Death †, or the Phytotoxicity of Trees

The use of natural products that can serve as natural herbicides and insecticides is a promising direction because of their greater safety for humans and environment. Secondary metabolites of plants that are toxic to plants and insects-allelochemicals-can be used as such products. Woody plants can produce allelochemicals, but they are studied much less than herbaceous species. Meanwhile, there is a problem of interaction of woody species with neighboring plants in the process of introduction or invasion, co-cultivation with agricultural crops (agroforestry) or in plantation forestry (multiclonal or multispecies plantations). This review describes woody plants with the greatest allelopathic potential, allelochemicals derived from them, and the prospects for their use as biopesticides. In addition, the achievement of and the prospects for the use of biotechnology methods in relation to the allelopathy of woody plants are presented and discussed.