Genome Sequence, Comparative Genome Analysis, and Expression Profiling of the Chitinase GH18 Gene Family in Cordyceps javanica Bd01

The fungus <i>Cordyceps javanica</i> is known for entomopathogenicity and effective in the control of various arthropods. Here, we aimed to reveal the chitinase GH18 gene family expansion through the high throughput sequencing of the genome of <i>C. javanica</i> strain Bd01 isolated from <i>Xylotrechus quadripes</i> larvae. The genome was 34 Mb in size with 9590 protein-coding genes. By comparative genome analysis, it was found that the family GH18 of chitinase genes was expanded in <i>C. javanica</i> Bd01. The phylogenetic analysis of 27 GH18 genes, compared with those from four other species, revealed that the genes could be categorized into three distinct groups based on their conserved domains. Genes within the same cluster exhibited shared protein motifs and orthologous relationships. The molecular mass of these GH18 genes ranged from 14.03 kDa to 81.41 kDa, while their theoretical isoelectric point (pI) values spanned from 4.40 to 7.92. Most chitinases were characterized as extracellular, hydrophilic, and thermostable proteins with a negative charge. Additionally, they demonstrated favorable in vivo half-life stability. A three-dimensional structural model of the GH18 protein was further generated using the SWISS-MODEL server. These findings establish a robust genomic framework elucidating the functional diversity, evolutionary conservation patterns, and mechanistic contributions of virulence-associated genetic determinants.