Organization and nucleotide sequence of a densovirus genome imply a host-dependent evolution of the parvoviruses.

The genome structure of a densovirus from a silkworm was determined by sequencing more than 85% of the complete genome DNA. This is the first report of the genome organization of an insect parvovirus deduced from the DNA sequence. In the viral genome, two large open reading frames designated 1 and 2 and one smaller open reading frame designated 3 were identified. The first two open reading frames shared the same strand, while the third was found in the complementary sequence. Computer analysis suggested that open reading frame 2 may encode all four structural proteins. The genome organization and a part of the nucleotide sequence were conserved among the insect densovirus, rodent parvoviruses, and a human dependovirus. These viruses may have diverged from a common ancestor.