Morphology, phylogeny, mitogenomics and metagenomics reveal a new entomopathogenic fungus Ophiocordycepsnujiangensis (Hypocreales, Ophiocordycipitaceae) from Southwestern China

Abstract

Ophiocordyceps contains the largest number of Cordyceps sensu lato, various species of which are of great medicinal value. In this study, a new entomopathogenic fungus, Ophiocordycepsnujiangensis, from Yunnan in southwestern China, was described using morphological, phylogenetic, and mitogenomic evidence, and its fungal community composition was identified. It was morphologically characterized by a solitary, woody, and dark brown stromata, smooth-walled and septate hyphae, solitary and gradually tapering conidiogenous cells with plenty of warty protrusions, and oval or fusiform conidia (6.4-11.2 × 3.7-6.4 µm) with mucinous sheath. The phylogenetic location of O.nujiangensis was determined based on the Bayesian inference (BI) and the maximum likelihood (ML) analyses by concatenating nrSSU, nrLSU, tef-1a, rpb1, and rpb2 datasets, and ten mitochondrial protein-coding genes (PCGs) datasets (atp6, atp9, cob, cox2, nad1, nad2, nad3, nad4, nad4L, and nad5). Phylogenetic analyses revealed that O.nujiangensis belonged to the Hirsutellasinensis subclade within the Hirsutella clade of Ophiocordyceps. And O.nujiangensis was phylogenetically clustered with O.karstii, O.liangshanensis, and O.sinensis. Simultaneously, five fungal phyla and 151 fungal genera were recognized in the analysis of the fungal community of O.nujiangensis. The fungal community composition differed from that of O.sinensis, and differences in the microbial community composition of closely related species might be appropriate as further evidence for taxonomy.

Keywords: Ophiocordycepsnujiangensis; microbial community; mitochondrial genome; new species; phylogenetic analyses.

Figure 1.

Phylogenetic placement of Ophiocordycepsnujiangensis inferred from the Bayesian inference (BI) and the maximum likelihood (ML) analyses by concatenating nrSSU, nrLSU, tef-1a, rpb1, and rpb2 datasets. The BI posterior probabilities (≥ 0.5) and the ML bootstrap values (≥ 50%) were indicated at the nodes. The specimens analyzed in this study were shown in bold type.

Figure 2.

Phylogenetic tree of Hypocreales based on the Bayesian inference (BI) and the maximum likelihood (ML) analyses of 10 PCGs. The 10 PCG genes included atp6, atp9, cob, cox2, nad1, nad2, nad3, nad4, nad4L and nad5. The values at the nodes were the BI posterior probabilities and the ML bootstrap proportions, respectively. The specimen analyzed in this study was given in bold type.

Figure 3.

OphiocordycepsnujiangensisA intact wild material B colony obverse on PDA with peptone and yeast extract powder C colony reverse on PDA with peptone and yeast extract powder D conidiogenous cells E–G conidiogenous cells and conidia H–L conidia. Scale bars: 3 cm (A); 2 cm (B, C); 20 µm (D–G); 5 µm (H–L).

Figure 4.

Composition of fungal community inhabiting Ophiocordycepsnujiangensis. A Composition of fungal community on phylum level. B Composition of fungal community on genus level. C Community heatmap analysis of the four specimens on genus level.