Comparative genomics and transcriptomics analyses reveal divergent lifestyle features of nematode endoparasitic fungus Hirsutella minnesotensis.
Bottom Line: Its genome was de novo sequenced and compared with five entomopathogenic fungi in the Hypocreales and three nematode-trapping fungi in the Orbiliales (Ascomycota).Those results indicate that H. minnesotensis has evolved different mechanism for nematode endoparasitism compared with nematode-trapping fungi.Genome and transcriptome analyses provided comprehensive understanding of the evolution and lifestyle of nematode endoparasitism.
Affiliation: State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China University of Chinese Academy of Sciences, Beijing, China.Show MeSH
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Mentions: The most enriched secreted protease family in H. minnesotensis and other reference fungi are the serine proteases, which comprise approximately 50% of all secreted proteases (supplementary table S8, Supplementary Material online). Serine proteases, especially the subtilases (affiliated into two families: The subtilisin-like protease S8 and the serine-carboxyl protease S53), are involved in lethal activity and the infection process of nematodes (Yang et al. 2005; Wang et al. 2007, 2009). They also assist in the infection processes of entomopathogenic fungi by degrading host cuticles, providing nutrition and disabling antimicrobial peptides (Bagga et al. 2004; Gao et al. 2011). Fewer secreted subtilase coding genes were identified in H. minnesotensis compared with the insect pathogen Me. robertsii and trapping fungi A. oligospora and Mo. haptotylum. A phylogenetic tree based on the conserved enzymatic S8/S53-subtilisin/kexin/sedolisin domains (PF00082) revealed that subtilase genes in the endoparasitic fungus diverged from those of insect fungi, supporting the origin of endoparasitic species from insect fungi and their similar functions in protein degradation. Compared with insect fungi, S53 serine proteases, which adapt to the specific insect hosts coupled with S8 proteases (Muszewska et al. 2011), have been lost from nematode-trapping and endoparasitic fungi (fig. 3, Clade A). Although they both belong to the cuticle degrading proteases, the subtilases from nematode-trapping and endoparasitic fungus are not grouped together. Most of the subtilases from trapping fungi only contain the enzymatic domain, whereas subtilases from the endoparasitic fungus contain other functional domains (fig. 3, Clades B–E), such as an N-terminal subtilisin propeptide (proteinase inhibitor I9, PF05922), the cleavage of which activates the enzyme; or the DUF1034 domain (Domain of Unknown Function 1034, PF06280) embedded with proteinase associated (PA, PF02225) domain, which may be involved in recognition of the protein by vacuolar sorting mechanisms (Luo and Hofmann 2001). Therefore, subtilases of nematode endoparasitic fungus and trapping fungi have evolved different functional domain architectures.Fig. 3.—
Affiliation: State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China University of Chinese Academy of Sciences, Beijing, China.