RNA-Seq de Novo Assembly and Differential Transcriptome Analysis of Chaga (Inonotus obliquus) Cultured with Different Betulin Sources and the Regulation of Genes Involved in Terpenoid Biosynthesis.

Fradj Fradj,Germain Germain,Awwad Awwad,De Montigny De Montigny,Gonçalves Dos Santos Gonçalves Dos Santos,Boumghar Boumghar,Desgagné-Penix Desgagné-Penix

doi:10.3390/ijms20184334

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https://doi.org/10.3390/ijms20184334

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Abstract

Chaga (Inonotus obliquus) is a medicinal fungus used in traditional medicine of Native American and North Eurasian cultures. Several studies have demonstrated the medicinal properties of chaga’s bioactive molecules. For example, several terpenoids (e.g., betulin, betulinic acid and inotodiol) isolated from I. obliquus cells have proven effectiveness in treating different types of tumor cells. However, the molecular mechanisms and regulation underlying the biosynthesis of chaga terpenoids remain unknown. In this study, we report on the optimization of growing conditions for cultured I. obliquus in presence of different betulin sources (e.g., betulin or white birch bark). It was found that better results were obtained for a liquid culture pH 6.2 at 28 °C. In addition, a de novo assembly and characterization of I. obliquus transcriptome in these growth conditions using Illumina technology was performed. A total of 219,288,500 clean reads were generated, allowing for the identification of 20,072 transcripts of I. obliquus including transcripts involved in terpenoid biosynthesis. The differential expression of these genes was confirmed by quantitative-PCR. This study provides new insights on the molecular mechanisms and regulation of I. obliquus terpenoid production. It also contributes useful molecular resources for gene prediction or the development of biotechnologies for the alternative production of terpenoids.

Highlights

Inonotus obliquus, a member of the Hymenochaetaceae family of Basidiomycetes, is a medicinal fungus used in the traditional medicine of Native American and North Eurasian cultures
The best growing conditions in liquid and solid cultures were determined for optimal production yield of Inonotus obliquus mycelia
We provide the first transcriptomic report generated by next-generation sequencing (Illumina HiSeq4000) of the medicinal fungus chaga, I. obliquus, grown under different conditions

Summary

Introduction

A member of the Hymenochaetaceae family of Basidiomycetes, is a medicinal fungus used in the traditional medicine of Native American and North Eurasian cultures. Studies have revealed that the extract of I. obliquus contains biologically active molecules derived from the specialized metabolism, supporting the effectiveness of chaga in traditional medicine These specialized metabolites (e.g., polysaccharides, polyphenols and terpenoids) are responsible for I. obliquus’s medicinal effects including those of the antioxidant [1,2,3,4,5,6,7,8,9,10,11], antibacterial [1,7,12,13], anti-diabetic [14,15,16,17,18,19], and anticancer [16,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37] types

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