Genomic Analyses of the Fungus sp. Isolated from the Chinese White Wax Scale Insect Reveals Its Symbiotic Character.

The Chinese white wax scale, , is an insect native to China. It harbors a variety of microbes. The fungus was isolated from and genome sequenced in this study. A fungal cytotoxicity assay was performed on the cell line C6/36. The assembled sp. genome was 39.55 Mb and consisted of 14,174 genes. The coding sequences accounted for 50.75% of the entire genome. Functional pathway analyses showed that sp. possesses complete pathways for the biosynthesis of 20 amino acids, 10 of which lacks. It also had complementary genes in the vitamin B groups synthesis pathways. Secondary metabolism prediction showed many gene clusters that produce polyketide. Additionally, a large number of genes associated with 'reduced virulence' in the genome were annotated with the Pathogen-Host Interaction database. A total of 651 genes encoding carbohydrate-active enzymes were predicted to be mostly involved in plant polysaccharide degradation. Pan-specific genomic analyses showed that genes unique to sp. were enriched in the pathways related to amino acid metabolism and secondary metabolism. GO annotation analysis yielded similar results. The top COG categories were 'carbohydrate transport and metabolism', 'lipid transport and metabolism', and 'secondary metabolite biosynthesis, transport and catabolism'. Phylogenetic analyses based on gene family and pan genes showed that sp is clustered together with species from the Didymosphaeriaceae family. A multi-locus sequence analysis showed that it converged with the same branch as and they formed one group with fungi from the genus. To validate the in vitro toxicity of sp., a cytotoxicity assay was performed. The results showed that medium-cultured sp. had no harmful effect on cell viability. No toxins were secreted by the fungus during growth. Our results imply that . may establish a symbiotic relationship with the host to supply complementary nutrition to .