The Plutella xylostella granulovirus (PxGV) genome DNA was sequenced and the predicted open reading frames (ORFs) were compared to genes of the first-sequenced GV, Xestia c-nigrum GV (XcGV), and those from other baculoviruses and organisms. PxGV DNA has a size of 100,999 bp with a G + C content of 40.7%. The analysis predicted 120 ORFs with a size of 150 nucleotides or larger that showed minimal overlap. Blast searches followed by a comparison of ORF arrangement with those of completely sequenced baculovirus genomes showed the presence of 102 homologs to other genes in the database. Among them, 74 and 100 were homologous to genes of Autographa californica NPV (AcMNPV) and XcGV, respectively. A striking feature of the relationship between the genomes of PxGV and XcGV was the conservation of the order and orientation of homologous genes. Even though the XcGV genome is much larger than that of PxGV (178 vs 101 kb) and had many more predicted ORFs (181 vs 120) with an average amino acid sequence relatedness of 42%, the order and orientation of almost all homologous genes was conserved. The PxGV genome contained four homologous regions (hrs), each with 10 to 23 repeated sequences of 101 to 105 nucleotides containing a 15-bp imperfect palindrome in the center of the repeats.

Milk vetch dwarf virus (MDV) is a member of the proposed genus

Nucleotide sequence analyses of cDNAs derived from the double-stranded RNA genome segments 6 and 7 (S6 and S7) of Bombyx mori cypovirus 1 (BmCPV-1) have revealed that they consist of 1796 and 1501 nucleotides encoding putative proteins of 561 and 448 amino acids with molecular masses of 63 604 and 49 875 (p64 and p50), respectively. The amino acid sequence of p64, which has a high leucine residue content (10 %), contains a leucine zipper motif. Antiserum raised against p64 specifically bound to a viral structural protein of ca. 68 kDa (V4), while antiserum against p50, which specifically bound to a protein of ca. 56 kDa in BmN4 cells infected with BmCPV-1, reacted with a cluster of four viral structural proteins ranging from ca. 34 to 40 kDa (V5). These observations indicate that p50 might be cleaved to V5 during the formation of virus particles.Cypoviruses (CPVs) of the family Reoviridae infect midgut epithelial cells of a wide range of insects (Payne & Mertens, 1983 ;Belloncik, 1989). The CPV capsid contains a 10-segmented double-stranded (ds) RNA genome (S1-S10) (FujiiKawata et al., 1970) and five structural proteins (V1-V5) (Payne & Rivers, 1976 ;McCrae & Mertens, 1983 ;Payne & Mertens, 1983). Recently, it was reported that the CPV particle has a single-shelled capsid and that there are two sizes of protrusions on the capsid shells. V3 and V5 are likely candidates for these protrusions (Zhang et al., 1999). However, we could not speculate further on the possible structure of the CPV particle comprising these structural proteins because no Author for correspondence : Kyoji Hagiwara.Fax j81 75 724 7990. e-mail hagiwara!ipc.kit.ac.jpThe nucleotide sequence data reported in this paper will appear in the DDBJ/EMBL/GenBank nucleotide sequence databases with the accession nos AB030014 and AB030015.sequence data are available. Thus, for elucidation of the molecular architecture of the CPV particle it is important to determine the nucleotide sequences of RNA segments and identify the encoded structural proteins. For Bombyx mori cypovirus 1 (BmCPV-1), we have already determined the complete nucleotide sequences of S8, S9 and S10, which encode nonstructural proteins (Hagiwara et al., 1998 a, b ;Miyajima et al., 1998). Here, we report the complete nucleotide sequences of BmCPV-1 S6 and S7, encoding the viral structural proteins V4 and V5, respectively.To obtain full-length cDNAs of S6 and S7, genomic dsRNA of BmCPV-1 was separated by 0n8 % agarose gel electrophoresis, and S6 and S7 dsRNAs were purified after being excised from the gel. The S6 and S7 dsRNAs were converted to cDNAs by a sequence-independent RT-PCR amplification method (Paul et al., 1992). The 3h-terminal region of 5h-phosphorylated primers was blocked by NH # (primer 1, 5h PO % -CCCGGATCCGTCGACGAATTCTTT-NH # 3h) to prevent concatenation of primer 1 in subsequent dsRNA\DNA ligation reactions. Then, primer 1 was ligated to both 3h ends of the purified dsRNA segment (S6 or S7) using T4 RNA ligase, and reverse transcription was performed using primer 2 (5h A...

No abstract

The Autographa californica nucleopolyhedrovirus (AcMNPV) does not infect the silkworm and molecular studies on silkworm insusceptibility have not been performed. In cultured cells of the silkworm, the expression of viral genes has been reported. The expression of AcMNPV genes and their effect in vivo and in vitro was studied. In this study, the early gene, the ecdysteroid UDP-glucosyltransferase (egt) gene of AcMNPV, which inactivates the insect moulting hormone by sugar conjugation, was examined to determine whether it would alter the growth of the silkworm. Using wild-type (wt) AcMNPV, the egt gene deletion virus (vEGTDEL), and the virus carrying the egt promoter-lacZ cassette in vEGTDEL (vEGTZ), the egt promoterdriven expression in cultured cells and in nonproductive infection of the silkworm was charac-