ANALYSIS OF GENETIC INFORMATION OF AN INSECT PICORNA-LIKE VIRUS, INFECTIOUS FLACHERIE VIRUS OF SILKWORM - EVIDENCE FOR EVOLUTIONARY RELATIONSHIPS AMONG INSECT, MAMMALIAN AND PLANT PICORNA(-LIKE) VIRUSES

We synthesized the cDNAs of an insect picornavirus, infectious flacher ie virus of silkworm (IFV), genomic RNA and inserted it into a bacteri al plasmid (pUC119). The 9650 nucleotides (nts) sequence except for th e poly(A) tail was obtained from the cloned cDNAs, and the sequence in tegrity was confirmed by primer extension and direct RNA sequencing. T he sequence has a large open reading frame (ORF) of 9255 nts (3085 cod ons) flanked by the short 5' non-coding region (156 nts) and by the ra ther long 3' non-coding (239 nts). The structural proteins VP3, 4, 1 a nd 2 were located at the N-terminus of the polyprotein in this order a nd were preceded by a tentative small peptide. Computer analysis ident ified the sequences similar to the consensus sequences of 2C (helicase ?), 3C (protease), and 3D (RNA polymerase) conserved among mammalian a nd plant picorna(-like) viruses. In addition, the predicted genome org anization of IFV was quite similar to those of picornaviruses. Further analyses of the characteristics of the genome structure and a tentati ve phylogenetic tree constructed on the basis of the amino acid sequen ce similarity emphasized the evolutionary relationships among the inse ct and plant viruses.