Characterization of the Ergosterol Biosynthesis Pathway in Ceratocystidaceae.

Mohammad Sayari,Brenda D Wingfield,Saleh Rahimlou,Almuth Hammerbacher,Emma T Steenkamp,Magrieta A Van Der Nest

doi:10.3390/jof7030237

Abstract

Terpenes represent the biggest group of natural compounds on earth. This large class of organic hydrocarbons is distributed among all cellular organisms, including fungi. The different classes of terpenes produced by fungi are mono, sesqui, di- and triterpenes, although triterpene ergosterol is the main sterol identified in cell membranes of these organisms. The availability of genomic data from members in the Ceratocystidaceae enabled the detection and characterization of the genes encoding the enzymes in the mevalonate and ergosterol biosynthetic pathways. Using a bioinformatics approach, fungal orthologs of sterol biosynthesis genes in nine different species of the Ceratocystidaceae were identified. Ergosterol and some of the intermediates in the pathway were also detected in seven species (Ceratocystis manginecans, C. adiposa, Huntiella moniliformis, Thielaviopsis punctulata, Bretziella fagacearum, Endoconidiophora polonica and Davidsoniella virescens), using gas chromatography-mass spectrometry analysis. The average ergosterol content differed among different genera of Ceratocystidaceae. We also identified all possible terpene related genes and possible biosynthetic clusters in the genomes used in this study. We found a highly conserved terpene biosynthesis gene cluster containing some genes encoding ergosterol biosynthesis enzymes in the analysed genomes. An additional possible terpene gene cluster was also identified in all of the Ceratocystidaceae. We also evaluated the sensitivity of the Ceratocystidaceae to a triazole fungicide that inhibits ergosterol synthesis. The results showed that different members of this family behave differently when exposed to different concentrations of triazole tebuconazole.

Highlights

Fungi produce a large variety of terpenoids that form part of a structurally and functionally diverse class of natural compounds [1]
Ergosterol and steroid biosynthesis pathways have been extensively examined in model fungi, little is known about these pathways in non-model fungi, including those in the economically important Ceratocystidaceae
The current study presents the first report of sterols, and ergosterol, in particular, produced by Ceratocystidaceae, as well as the putative biosynthetic pathway underlying ergosterol biosynthesis in these fungi

Summary

Introduction

Fungi produce a large variety of terpenoids that form part of a structurally and functionally diverse class of natural compounds [1] They are involved in an array of biological processes ranging from those needed for the adaptation to particular environmental niches to those needed for the interaction with other organisms [2]. Ergosterol (24-methylcholesta-5, 7, 22trien3b-ol) is their major sterol [5], with the main exception being primitive fungi such as those in the Chytridiomycota where cholesterol (cholest-5-en-3β-ol) is the main sterol [6] These sterols are primarily found in cell membranes where it has diverse functions including processes essential for growth and development, the regulation of cell wall permeability, and adaptation to stress [7]

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