Transcriptome analysis and identification of genes related to terpenoid biosynthesis in Cinnamomum camphora

Caihui Chen,Yongjie Zheng,Zhiting Li,Meng Xu,Yangfang Wu,Yongda Zhong,Li-An Xu

doi:10.1186/s12864-018-4941-1

Caihui Chen, Yongjie Zheng + Show 5 more

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https://doi.org/10.1186/s12864-018-4941-1

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Abstract

BackgroundCinnamomum camphora has been cultivated as an economically important tree for its medicinal and aromatic properties. Selective breeding has produced Cinnamomum plants for special uses, including spice strains with characteristic flavors and aromas and high-potency medicinal cultivars. The molecular biology underlying terpenoid biosynthesis is still unexplored.ResultsGas chromatography-mass spectrometry was used to analyze the differences in contents and compositions of essential oil terpenoids in linalool- and borneol-type chemotypes of C. camphora. The data revealed that the essential oils consist primarily of monoterpenes with only very minor quantities of sesquiterpenes and diterpenes and that the essential oil differs in different chemotypes of C. camphora, with higher yields of (−)-borneol from the borneol-type than from the linalool-type. To study the terpenoid biosynthesis of signature compounds of the major monoterpenes, we performed RNA sequencing to profile the leaf transcriptomes of the two chemotypes of C. camphora. A total of 23.76 Gb clean data was generated from two chemotypes and assembled into 156,184 unigenes. The total length, average length, N50 and GC content of unigenes were 155,645,929 bp, 997 bp, 1430 bp, and 46.5%, respectively. Among them, 76,421 unigenes were annotated by publicly available databases, of which 67 candidate unigenes were identified to be involved in terpenoid biosynthesis in C. camphora. A total of 2863 unigenes were identified to be differentially expression between borneol-type and linalool-type, including 1714 up-regulated and 1149 down-regulated unigenes. Most genes encoding proteins involved in terpenoid precursor MVA and MEP pathways were expressed in similar levels in both chemotypes of C. camphora. In addition, 10 and 17 DEGs were significantly enriched in the terpene synthase activity and oxidoreductase activity terms of their directed acyclic graphs (DAG), respectively. Three monoterpene synthase genes, TPS14-like1, TPS14-like2 and TPS14-like3 were up-regulated in the borneol-type compared to the linalool-type, and their expression levels were further verified using quantitative real-time PCR.ConclusionsThis study provides a global overview of gene expression patterns related to terpenoid biosynthesis in C. camphora, and could contribute to a better understanding of the differential accumulation of terpenoids in different C. camphora chemotypes.

Highlights

Cinnamomum camphora has been cultivated as an economically important tree for its medicinal and aromatic properties
The composition of leaf extracts from different chemotypes of C. camphora Specimens of C. camphora leaves from two chemotypes (F_L1 and F_L2 were linalool-types, L_L1 and L_L2 were borneol-types) were obtained from the garden of Jiangxi Academy of Forestry and the leaf extracts were isolated by water distillation
The leaf essential oil extracts of the linalool-type remained as oil liquids, whereas that of the borneol-type formed crystals (Fig. 1b)

Summary

Introduction

Cinnamomum camphora has been cultivated as an economically important tree for its medicinal and aromatic properties. Cinnamomum camphora, a member of the Lauraceae family, is an evergreen broad-leaf tree indigenous to southern China and Japan [1]. The essential oil or crystal distilled from C. camphora has considerable economic importance as a source of food preservative and additive, and as raw materials for the cosmetic and pharmaceutical industries. According to the signature constituent in leaf, C. camphora was classified into at least five different chemical variants (chemotypes), including linalool- (58–92%), borneol- (67–82%), camphor- (54–97%), cineole- (32–52%), and nerolidol-types (16–57%) [4, 5]. C. camphora has become of increasing importance as a source of essential oils, especially for the production of natural borneol and linalool [6]. Natural borneol has been used to increase the permeabilities of the intestinal mucosa and blood-brain barrier to improve the oral bioavailability of some poorly permeable drugs [7]

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