A First Insight into North American Plant Pathogenic Fungi Armillaria Sinapina Transcriptome.

Narimene Fradj,Fatima Awwad,Yacine Boumghar,Isabel Desgagné-Penix,Nicolas De Montigny,Hugo Germain,Natacha Mérindol

doi:10.3390/biology9070153

Abstract

Armillaria sinapina, a fungal pathogen of primary timber species of North American forests, causes white root rot disease that ultimately kills the trees. A more detailed understanding of the molecular mechanisms underlying this illness will support future developments on disease resistance and management, as well as in the decomposition of cellulosic material for further use. In this study, RNA-Seq technology was used to compare the transcriptome profiles of A. sinapina fungal culture grown in yeast malt broth medium supplemented or not with betulin, a natural compound of the terpenoid group found in abundance in white birch bark. This was done to identify enzyme transcripts involved in the metabolism (redox reaction) of betulin into betulinic acid, a potent anticancer drug. De novo assembly and characterization of A. sinapina transcriptome was performed using Illumina technology. A total of 170,592,464 reads were generated, then 273,561 transcripts were characterized. Approximately, 53% of transcripts could be identified using public databases with several metabolic pathways represented. A total of 11 transcripts involved in terpenoid biosynthesis were identified. In addition, 25 gene transcripts that could play a significant role in lignin degradation were uncovered, as well as several redox enzymes of the cytochromes P450 family. To our knowledge, this research is the first transcriptomic study carried out on A. sinapina.

Highlights

In forest ecosystems, fungi represent a complex group of microorganisms that vary from uni- to multicellular entities
We investigated the influence of betulin on A. sinapina transcriptome to better understand the genetic response to this compound, as well as to determine its impact on the enzymes involved in degradation of the cell walls of birch bark, and to potentially discover new genes involved in the biotransformation of betulin into betulinic acid, in an effort to valorize forest residues
RNA was extracted from biological replicates of cultured A. sinapina in the absence or presence of the terpenoid substrate betulin (BET)

Summary

Introduction

In forest ecosystems, fungi represent a complex group of microorganisms that vary from uni- to multicellular entities. They are capable of developing in very different lifestyles, from saprophytes to plants, to animal and human pathogens, parasites and symbionts. Through their adaptative capacities, these organisms could play roles as biocatalyst agents [1]. Some fungi have the ability to interact with each other and with other ecosystem components in a multi-dimensional and complex way within the forest ecosystems [1,2,3,4]. Armillaria species are globally distributed in natural and planted forests of temperate, boreal and tropical ecosystems. Armillaria sp. are specific pathogens that colonize living trees and cause white rot

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