Comprehensive codon usage analysis of rice black-streaked dwarf virus based on P8 and P10 protein coding sequences.

Rice black-streaked dwarf virus (RBSDV) belongs to the genus Fijivirus of the family Reoviridae and is an important pathogen that damages rice, maize and wheat worldwide. Previously, several reports have described the genetic variation and population structure of RBSDV. However, the details of the evolutionary changes, synonymous codon usage patterns and host adaptation of the virus are largely unclear. Here, we performed a detailed analysis of the codon usage and host adaptability of RBSDV based on 130 full-length P8 and 234 full-length P10 sequences. Infrequent recombination and frequent segment reassortment influence the genomic evolution of RBSDV. Our phylogenetic analysis found three and four lineages based on the P8 and P10 non-recombinant sequences respectively. We found relatively stable and conserved genomic composition with lower codon usage choice in the RBSDV P8 and P10 protein coding sequences. Both ENC-plot and neutrality-plot analyses showed that natural selection is the key factor that shapes the codon usage pattern of RBSDV. Codon adaptation index (CAI), relative codon deoptimization index (RCDI) and similarity index (SiD) analyses indicated strong correlation between RBSDV and rice rather than maize, wheat or Laodelphax striatellus. Our study provides deep insight into the evaluation of the codon usage pattern and adaptive evolution of RBSDV based on P8 and P10 sequences and should be taken into consideration for the prevention and control of this virus.