A Comprehensive Comparative Analysis on the Codon Usage Bias of DNA Polymerase Genes in Invertebrate Iridescent Viruses

Abstract

Invertebrate iridescent viruses (IIVs) are classified as double-stranded DNA viruses within the Iridoviridae family. IIVs are viruses that infect invertebrate hosts, causing symptoms that vary in intensity from slight reductions in host fitness to systemic disease. Numerous earlier investigations have provided insights into the genomic, proteomic, and transcriptional analyses of invertebrate iridescent viruses. However, the codon usage bias (CUB) of IIVs has yet to be fully understood. In order to gain a more profound insight into the evolutionary features of IIVs, we conducted an extensive analysis of the codon usage patterns in the DNA polymerase genes (DNA pol genes) of 12 invertebrate iridescent viruses. The analysis of both nucleotide composition and relative synonymous codon usage (RSCU) indicated a higher prevalence of AT-ended codons in the DNA pol genes of IIVs. Additionally, a low codon usage bias was determined from the effective number of codons (ENC) value. Analyses of ENC-GC3s plot, neutrality plot, and parity rule 2 plot illustrated that the codon usage patterns in IIVs DNA pol genes were influenced by both natural selection and mutational pressure. This investigation holds significance as it has delineated the codon usage patterns within the DNA pol genes of IIVs and has furnished crucial data for a foundational study of their evolutionary aspects.