Molecular anatomy of Chilo iridescent virus genome and the evolution of viral genes

Chilo iridescent virus (CIV) or Insect iridescent virus 6 (IIV-6) is the type species of the genus iridovirus, a member of the Iridoviridae family. CIV is highly pathogenic for a variety of insect larvae and this implicates a possible use as a biological insecticide. CIV progeny and assembly occur in the cytoplasm of the infected cell and accumulate in the fatbody of the infected insects. Since the discovery of CIV in 1966, many attempts were made to elucidate the viral genome structure and the amino acid sequences of different viral gene products. The elucidation of the coding capacity and strategy of CIV was the first step towards understanding the underlying mechanisms of viral infection, replication and virus-host interaction. The virions contain a single linear ds DNA molecule that is circularly permuted and terminally redundant. The coding capacity of the CIV genome was determined by the analysis of the complete DNA nucleotide sequence consisting of 212,482 bp that represent 468 open reading frames encoding for polypeptides ranging from 40 to 2432 amino acid residues. The analysis of the coding capacity of the CIV genome revealed that 50% (234 ORFs) of all identified ORFs (468 ORFs) were non-overlapping. The identification of several putative viral gene products including a DNA ligase and a viral antibiotic peptide is a powerful tool for the investigation of the phylogenetic relatedness of this evolutionary and ecologically relevant eukaryotic virus.