Chromosome level assembly and secondary metabolite potential of the parasitic fungus Cordyceps militaris

Glenna J Kramer,Justin R Nodwell

doi:10.1186/s12864-017-4307-0

Abstract

BackgroundCordyceps militaris is an insect pathogenic fungus that is prized for its use in traditional medicine. This and other entomopathogenic fungi are understudied sources for the discovery of new bioactive molecules. In this study, PacBio SMRT long read sequencing technology was used to sequence the genome of C. militaris with a focus on the genetic potential for secondary metabolite production in the genome assembly of this fungus.ResultsThis is first chromosome level assembly of a species in the Cordyceps genera. In this seven chromosome assembly of 33.6 Mba there were 9371 genes identified. Cordyceps militaris was determined to have the MAT 1-1-1 and MAT 1-1-2 mating type genes. Secondary metabolite analysis revealed the potential for at least 36 distinct metabolites from a variety of classes. Three of these gene clusters had homology with clusters producing desmethylbassianin, equisetin and emericellamide that had been studied in other fungi.ConclusionOur assembly and analysis has revealed that C. militaris has a wealth of gene clusters for secondary metabolite production distributed among seven chromosomes. The identification of these gene clusters will facilitate the future study and identification of the secondary metabolites produced by this entomopathogenic fungus.

Highlights

Cordyceps militaris is an insect pathogenic fungus that is prized for its use in traditional medicine
General genome features Purified genomic DNA isolated from culture of C. militaris grown up from a single colony was sequenced using the Pacific Biosciences platform using a sheared large insert library [14]
Of the 36 gene clusters identified in American Type Culture Collection (ATCC)®34164 by both the antiSMASH and SMURF algorithms (Additional file 2: Table S1), 3 clusters, III-1, V-6 and VII-5, are of particular interest as they have homology with gene clusters from other organisms that produce characterized natural products [39, 40]

Summary

Introduction

Cordyceps militaris is an insect pathogenic fungus that is prized for its use in traditional medicine. Entomopathogenic fungi are a fascinating group of insect parasitic microbes, which include species from a variety of different fungal taxa including Beauvaria, Hirsutella, Metarhizium Cordyceps and Ophiocordyceps (Fig. 1). These entomopathogenic fungi typically have a lifecycle in which the host is infected and is killed in the process of fungal propagation. As the insect’s body is used as a nutrient reservoir for growth, the insect’s behaviour is modified, eventually leading the host to die in an Ophiocordyceps sinensis, found in the mountains of Tibet, infects and kills ghost moth larvae to give the highly prized herbal remedy “dong chong xia cao,” which is believed to treat a plethora of disorders [1]. Ophiocordyceps unilateralis, known as the zombie-ant fungus, is noted for its pathogenic process in ants, which is characterized by particular behaviour

Methods

Results

Discussion

Conclusion