Infectious bronchitis viruses with naturally occurring genomic rearrangement and gene deletion

Faculty of Veterinary Science, Veterinary Clinical Centre, The University of Melbourne, 250 Princes Highway, Werribee, Victoria 3030, Australia.
Archives of Virology (Impact Factor: 2.39). 11/2010; 156(2):245-52. DOI: 10.1007/s00705-010-0850-6
Source: PubMed


Infectious bronchitis viruses (IBVs) are group III coronaviruses that infect poultry worldwide. Genetic variations, including whole-gene deletions, are key to IBV evolution. Australian subgroup 2 IBVs contain sequence insertions and multiple gene deletions that have resulted in a substantial genomic divergence from international IBVs. The genomic variations present in Australian IBVs were investigated and compared to those of another group III coronavirus, turkey coronavirus (TCoV). Open reading frames (ORFs) found throughout the genome of Australian IBVs were analogous in sequence and position to TCoV ORFs, except for ORF 4b, which appeared to be translocated to a different position in the subgroup 2 strains. Subgroup 2 strains were previously reported to lack genes 3a, 3b and 5a, with some also lacking 5b. Of these, however, genes 3b and 5b were found to be present but contained various mutations that may affect transcription. In this study, it was found that subgroup 2 IBVs have undergone a more substantial genomic rearrangements than previously thought.

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    • "Genes 3 and 5 are polycistronic and encode proteins 3a, 3b and E, and 5a and 5b respectively [35] [36]. There was previously reported to be an 'intergenic' region located between the genes M and 5 in the group 3 coronaviruses, IBV and TCoV, however recent reports have demonstrated the presence of two ORFs, 4b and 4c, in this region [37] [38] [39]. Another ORF, 6b, was also detected in these studies immediately downstream of the N gene. "
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