title: Characterization of repetitive DNA regions and methylated DNA in ascovirus genomes.
abstract: The accompanying phylogenetic study of large double-stranded DNA viruses based on their delta DNA polymerase genes suggests that ascoviruses (family ASCOVIRIDAE:) and iridoviruses (family IRIDOVIRIDAE:) are closely related and may share a common ancestor. This relationship was unexpected because of marked differences between these viruses. Iridoviruses produce icosahedral virions and occur broadly among vertebrates and invertebrates, whereas ascoviruses typically produce reniform or bacilliform virions and are restricted to insect hosts, primarily lepidopterans. Detailed comparisons of these two virus types are not possible because fundamental information on the properties of the virions and their genomes is lacking, especially for ascoviruses. To facilitate further investigation of the putative evolutionary relationship between ascoviruses and iridoviruses, the genomes of representative viruses from each family were compared with respect to physical configuration, presence of DNA repeats and degree of DNA methylation. Genomes from Spodoptera frugiperda (SfAV1), Heliothis virescens (HvAV3) and Diadromus pulchellus (DpAV4) ascoviruses were all found to be circular and partially superhelical and to contain large interspersed repeats of 1-3 kbp. Mosquito (IV type 3), lepidopteran (IV type 6) and isopod (IV type 31) iridovirus genomes were all linear and lacked large regions of repetitive DNA. Ascovirus and iridovirus genomes were methylated and one, DpAV4, had the highest degree of methylation of any reported animal DNA virus. The major differences in the physical and biochemical characteristics of ascoviruses and iridoviruses reported here provide a foundation for further studies of their relatedness while making their possible close relationship and divergence during evolution of even greater interest.
authors.affiliation: Department of Entomology and Interdepartmental Graduate Program in Genetics, University of California, Riverside, CA 92521, USA2.|IRBI, Groupe d'Etude des Parasites Moléculaires, UPRESA CNRS 6035, Faculté des Sciences, Parc de Grandmont, 37200 Tours, France1.
authors.forename: Yves
authors.initials: Y
authors.lastname: Bigot
authors.affiliation: Department of Entomology and Interdepartmental Graduate Program in Genetics, University of California, Riverside, CA 92521, USA2.|IRBI, Groupe d'Etude des Parasites Moléculaires, UPRESA CNRS 6035, Faculté des Sciences, Parc de Grandmont, 37200 Tours, France1.
authors.forename: Karine
authors.initials: K
authors.lastname: Stasiak
authors.affiliation: IRBI, Groupe d'Etude des Parasites Moléculaires, UPRESA CNRS 6035, Faculté des Sciences, Parc de Grandmont, 37200 Tours, France1.
authors.forename: Florence
authors.initials: F
authors.lastname: Rouleux-Bonnin
authors.affiliation: Department of Entomology and Interdepartmental Graduate Program in Genetics, University of California, Riverside, CA 92521, USA2.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Federici
mesh_terms: D000818:Animals; D002586:Cesium; D002712:Chlorides; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D019175:DNA Methylation; D004267:DNA Viruses / Q000235:genetics*; D004279:DNA, Viral / Q000235:genetics; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000032:analysis; D016521:Electrophoresis, Gel, Pulsed-Field; D019143:Evolution, Molecular; D016679:Genome, Viral; D007304:Insect Viruses / Q000235:genetics*; D017994:Iridovirus / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D015183:Restriction Mapping; D014461:Ultracentrifugation
chemical_list: D002712:Chlorides; D004279:DNA, Viral; D003841:Deoxycytidine; D002586:Cesium; C016569:5-methyldeoxycytidine; C028019:cesium chloride