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Chiloiridescent virus (CIV) or Insect iridescent virus 6(IIV-6) is the type species of the genus iridovirus, a member of the Iridoviridaefamily. 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.

Chiloiridescent virus (CIV), the type species of the genus Iridovirus, a member of the Iridoviridaefamily, is highly pathogenic for a variety of insect larvae. The virions contain a single linear ds DNA molecule that is circularly permuted and terminally redundant. The coding capacity and strategy of the CIV genome was elucidated by the analysis of the complete DNA nucleotide sequence of the viral genome (212,482 bp) using cycle sequencing by primer walking technology. Both DNA strands were sequenced independently and the average redundancy for each nucleotide was found to be 1.85. The base composition of the viral genomic DNA sequence was found to be 71.37% A+T and 28.63% G+C. The CIV genome contains 468 open reading frames (ORFs). The size of the individual viral gene products ranges between 40 and 2432 amino acids. The analysis of the coding capacity of the CIV genome revealed that 50% (234 ORFs) of all identified ORFs were nonoverlapping. The comparison of the deduced amino acid sequences to entries in protein data banks led to the identification of several genes with significant homologies, such as the two major subunits of the DNA-dependent RNA polymerase, DNA polymerase, protein kinase, thymidine and thymidylate kinase, thymidylate synthase, ribonucleoside-diphosphate reductase, major capsid protein, and others. The highest homologies were detected between putative viral gene products of CIV and lymphocystis disease virus of fish (LCDV). Although many CIV putative gene products showed significant homologies to the corresponding viral proteins of LCDV, no colinearity was detected when the coding strategies of the CIV and LCDV-1 were compared to each other. An intriguing result was the detection of a viral peptide of 53 amino acid residues (ORF 160L) showing high homology (identity/similarity: 60.0%/30.0%) to sillucin, an antibiotic peptide encoded by Rhizomucor pusillus.Iridovirus homologs of cellular genes possess particular implications for the molecular evolution of large DNA viruses.