Influencing elements of codon usage bias in Birnaviridae and its evolutionary analysis.

Birnaviridae is a family of double stranded (ds) RNA virus with non-enveloped virions and 2-segmented genomes. These viruses are known to cause diseases in many hosts. Virus of this family has affected the fish and poultry economy in a wide sector. Unevenness in the use of synonymous codons for a particular amino acid in the coding strand of DNA is known as codon usage bias (CUB). Codons that code the same amino acid are used with variable frequency in a variety of life forms. To understand the pattern of CUB in Birnaviridae, we carried out bioinformatics study to understand the properties of coding sequences of proteins. ENC value of Birnaviridae suggested low CUB. Nucleotide analysis revealed high GC content. Parameters such as RSCU values, nucleotide skewness, translational selection, parity plot and neutrality plot were studied to investigate the pattern of codon use and it was clear that both mutational pressure and natural selection contributed to the designing of CUB in Birnaviridae family. The neutrality plot revealed natural selection to dominate the structuring of CUB and hence remained the major CUB determinant in Birnaviridae. Outcome of our study exemplified the pattern of codon use in the Birnaviridae genomes and contributed the basic primary data for fundamental evolutionary research on them.