Analyses of nucleotide, codon and amino acids usages between peste des petits ruminants virus and rinderpest virus

Peste des petits ruminants virus (PPRV) and rinderpest virus (RPV) are two causative agents of an economically important disease for ruminants (i.e., sheep, cattle and goat). In this study, the nucleotide, codon and amino acid usages for PPRV and RPV have been analyzed by multivariate statistical methods. Relative synonymous codon usage (RSCU) analysis represents that ACG for Thr and GCG for Ala are selected with under-representation in both PPRV and RPV, and AGA for Arg in PPRV and AGG for Arg in RPV are used with over-representation. The usage of nucleotide pair (CpG) tends to be removed from viral genes of the two viruses, suggesting that other evolutionary forces take part in evolutionary processes for viral genes in addition to mutation pressure from nucleotide usage at the third codon position. The overall nucleotide usage of viral gene is not major factor in shaping synonymous codon usage patterns, while the nucleotide usages at the third codon position and the nucleotide pairs play important roles in shaping synonymous codon usage patterns. Although PPRV and RPV are closely related antigenically, the codon and amino acid usage patterns for viral genes represent a significant genetic diversity between PPRV and RPV. Moreover, the overall codon usage trends for viral genes between PPRV and RPV are mainly influenced by mutation pressure from nucleotide usage at the third codon position and translation selection from hosts. Taken together, this is first comprehensive analyses for nucleotide, codon and amino acid usages of viral genes of PPRV and RPV and the findings are expected to increase our understanding of evolutionary forces influencing viral evolutionary pathway and adaptation toward hosts.