Complete mitochondrial genome of the medicinal fungus Ophiocordyceps sinensis

Abstract

As part of a genome sequencing project for Ophiocordyceps sinensis, strain 1229, a complete mitochondrial (mt) genome was assembled as a single circular dsDNA of 157,510 bp, one of the largest reported for fungi. Conserved genes including the large and small rRNA subunits, 27 tRNA and 15 protein-coding genes, were identified. In addition, 58 non-conserved open reading frames (ncORFs) in the intergenic and intronic regions were also identified. Transcription analyses using RNA-Seq validated the expression of most conserved genes and ncORFs. Fifty-two introns (groups I and II) were found within conserved genes, accounting for 68.5% of the genome. Thirty-two homing endonucleases (HEs) with motif patterns LAGLIDADG (21) and GIY-YIG (11) were identified in group I introns. The ncORFs found in group II introns mostly encoded reverse transcriptases (RTs). As in other hypocrealean fungi, gene contents and order were found to be conserved in the mt genome of O. sinensis, but the genome size was enlarged by longer intergenic regions and numerous introns. Intergenic and intronic regions were composed of abundant repetitive sequences usually associated with mobile elements. It is likely that intronic ncORFs, which encode RTs and HEs, may have contributed to the enlarged mt genome of O. sinensis.

Cordyceps collected from Bhutan, an appropriate alternative of Cordyceps sinensis

“…In addition, mitochondrial COI and Cytb sequences in host insect of Bhutanese Cordyceps were 658 bp and 433 bp, and GC contents were 29.18% and 22.86%, respectively. Both mitochondrial COI and Cytb sequences suggested that species of host insect of Bhutanese Cordyceps belonged to Hepialidae sp (99% homologous)20, which was in accordance with those of C. sinensis 32122.…”

“…It is distributed on the Tibetan Plateau and its surrounding regions at an altitude above 3,000 m, including Tibet, Gansu, Qinghai, Sichuan, and Yunnan provinces in China and in certain areas such as the countries of Bhutan, India and Nepal on the southern flank of the Himalayas134. Usually, C. sinensis has been used for the prevention and treatment of a variety of diseases such as asthma, bronchitis, lung inflammation, nocturnal emissions, and night sweats567.…”

Comparison of different sequencing and assembly strategies for a repeat-rich fungal genome, Ophiocordyceps sinensis

“…Interestingly, the mitochondrial genome of this species is also expanded (157 Kb) compared with other hypocrealean species (from ~22 kb in Cordyceps bassiana to ~42 kb in Trichoderma reesei; Li et al, 2015). Long intergenic regions and numerous introns composing of abundant repetitive sequences which associate with mobile elements largely contributed to the mt genome expansion (Li et al, 2015). However, the genome expansion of O. sinensis experienced a different process which was driven by numerous retrotransposons (Hu et al, 2013).…”

“…usually have nuclear genomes of 30-50 Mb (www.ncbi.nlm.nih.gov/genome/browse/). Interestingly, the mitochondrial genome of this species is also expanded (157 Kb) compared with other hypocrealean species (from ~22 kb in Cordyceps bassiana to ~42 kb in Trichoderma reesei; Li et al, 2015). Long intergenic regions and numerous introns composing of abundant repetitive sequences which associate with mobile elements largely contributed to the mt genome expansion (Li et al, 2015).…”

The mitochondrial genome of the nematode endoparasitic fungus Hirsutella rhossiliensis

“…Note that the accession number of Ophiocordyceps sinensis has not yet been released. The complete mitochondrial genome of O. sinensis has been reported (Li et al 2015).…”