Abstract
Expression of viral DNA polymerase gene (pol) was examined in the midgut, fat body, silkgland and remaining carcass of larvae of the silkworm, Bombyx mori, infected with B. mori nuclear polyhedrosis virus (BmSNPV). Northern blot analysis detected a prominent viral pol transcript of approximately 3 kb and several other less prominent transcripts in these tissues. Mapping of the 5' end by RNase protection assay showed that the 3-kb pol transcript detected in the Northern blot analysis consisted of two species. These two species corresponded to the major and the largest transcripts, respectively, among seven viral pol transcripts unique to the infected tissues. Expression of each transcript varied considerably among tissues and with postinfection time. The abundance of overall pol transcripts coincided with those of DNA polymerase protein, viral DNA, viral polypeptides and polyhedrin in these tissues, with the exception of the carcass. These results suggest that the expression of viral pol transcripts is regulated differentially among tissues and during infection. They also suggest a possible role of viral early gene expression or viral DNA synthesis in the regulation of late and very late gene expression.
