Genetic variation of Chlorella viruses: Variable regions localized on the CVK2 genomic DNA

A physical map of the Chlorella virus CVK2 genomic DNA has been constructed based on a cosmid contig covering the entire genomic region. By using Sout hern blot analysis with 22 gene probes, the gene arrangement along the geno me was compared between CVK2 and PBCV-1, the prototypic member of Phycodnav iridae, whose genomic sequence is now available. The major rearrangements w ere (1) an insertion of a 20-kbp region around the left end of CVK2 DNA, (2 ) a duplication of the gene for major capsid protein in CVK2 DNA, (3) delet ions/insertions of some open reading frames, and (4) divergence in the term inal inverted repeat sequences. Despite these changes, extensive colinearit y was revealed between most of the genes along the CVK2 and PBCV-1 genomes. These data imply that the Chlorella Virus genome has an overall high degre e of genomic stability, encompassing specific islands of rearrangements. (C ) 1999 Academic Press.