Genome sequence of Isaria javanica and comparative genome analysis insights into family S53 peptidase evolution in fungal entomopathogens
The fungus Isaria javanica is an important entomopathogen that parasitizes various insects and is effective for pest control. In this study, we sequenced and assembled the genomes (IJ1G and IJ2G) of two I. javanica strains isolated from different insects. The genomes were approximately 35 Mb in size with 11,441 and 11,143 protein-coding genes, respectively. Using a phylogenomic approach, we evaluated genome evolution across five entomopathogenic fungi in Cordycipitaceae. By comparative genome analysis, it was found that family S53 serine peptidases were expanded in Cordycipitaceae entomopathogens, particularly in I. javanica. Gene duplication events were identified based on phylogenetic relationships inferred from 82 S53 peptidases within six entomopathogenic fungal genomes. Moreover, we found that carbohydrate-active enzymes and proteinases were the largest secretory protein groups encoded in the I. javanica genome, especially chitinases (GH18), serine and aspartic peptidases (S53, S08, S10, A01). Pathogenesis-related genes and genes for bacterial-like toxins and secondary metabolites were also identified. By comparative transcriptome analysis, differentially expressed genes in response to insect nutrients (in vitro) were identified. Moreover, most S53 peptidases were detected to be significantly upregulated during the initial fungal infection process in insects (in vivo) by RT-qPCR. Our results provide new clues about understanding evolution of pathogenic proteases and may suggest that abundant S53 peptidases in the I. javanica genome may contribute to its effective parasitism on various insects.
KeywordsIsaria javanica Entomopathogen Serine peptidase S53 family Gene family expansion Gene duplication Genome evolution
L.R. assembled and annotated the genomic and transcriptomic data. L.R. and X.C. analysed the genomic data. X.Z. and M.Z. performed RT-qPCR. B. Xin and F.Q. prepared fungal materials, and Y.G. prepared insect materials. Q.H. provided the fungal strains. X. C, R.L. and X.Z. wrote the manuscript. B. Xie and X.C. designed the research and revised the manuscript.
The research was financially supported by the National Key Research and Development (R&D) Plan of China (2018YFD0200802, 2016YFC1201100).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interests.
This paper is an original work. It has not been submitted elsewhere and under consideration in any other Journal. It does not contain any studies with human participants or vertebrates performed by any of the authors.
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