Comparative transcriptome analysis to identify putative genes involved in thymol biosynthesis pathway in medicinal plant Trachyspermum ammi L.

Mehdi Soltani Howyzeh,Vahid Shariati J,Seyed Ahmad Sadat Noori,Mahboubeh Amiripour

doi:10.1038/s41598-018-31618-9

Mehdi Soltani Howyzeh, Vahid Shariati J + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-31618-9

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Abstract

Thymol, as a dietary monoterpene, is a phenol derivative of cymene, which is the major component of the essential oil of Trachyspermum ammi (L.). It shows multiple biological activities: antifungal, antibacterial, antivirus and anti-inflammatory. T. ammi, commonly known as ajowan, belongs to Apiaceae and is an important medicinal seed spice. To identify the putative genes involved in thymol and other monoterpene biosynthesis, we provided transcriptomes of four inflorescence tissues of two ajowan ecotypes, containing different thymol yield. This study has detected the genes encoding enzymes for the go-between stages of the terpenoid biosynthesis pathways. A large number of unigenes, differentially expressed between four inflorescence tissues of two ajowan ecotypes, was revealed by a transcriptome analysis. Furthermore, differentially expressed unigenes encoding dehydrogenases, transcription factors, and cytochrome P450s, which might be associated with terpenoid diversity in T. ammi, were identified. The sequencing data obtained in this study formed a valuable repository of genetic information for an understanding of the formation of the main constituents of ajowan essential oil and functional analysis of thymol-specific genes. Comparative transcriptome analysis led to the development of new resources for a functional breeding of ajowan.

Highlights

Terpenoids are the biggest group of plant secondary metabolites, and interest in isolated terpenoids has been growing in recent years due to their pharmaceutical or pharmacological utility
Short-read transcriptome sequencing from the inflorescence tissues of two ecotypes (Arak and Shiraz) was carried out (Fig. 2)
Phytochemical analyses of inflorescence tissues of Arak and Shiraz ecotypes showed that three components—thymol, γ-terpinene, and p-cymene—to be the main components of ajowan essential oils, comprising 98% of essential oil components in the studied ecotypes

Summary

Introduction

Terpenoids are the biggest group of plant secondary metabolites, and interest in isolated terpenoids has been growing in recent years due to their pharmaceutical or pharmacological utility. Medicinal plant taxa cover a wide range of plants, which produce various classes of natural products but mostly have limited genomic or transcriptomic resources Novel genes from these non-model species can be detect by the generation sequencing (NGS) techniques as valuable genomic tools, which have been used for identifying and characterizing secondary metabolism genes and their pathways[23]. It can be used for different goals, such as transcriptome quantification, differential expression, transcript annotation, novel transcript identification, molecular marker development, alternative splicing[27,28,29], and polymorphism detection at the transcriptome level[30,31] This technique, as an efficient, cost-effective, and high-throughput technology, can be performed for plant species with or without a genome reference, making it a suitable alternative for analyzing non-model plant species without any genomic sequence source[32,33]. The transcriptome was annotated and the pathways of thymol and other terpenoid were analyzed

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