Identification of virus-specific polypeptides and translatable mRNAs in the isolated pupal abdomens of the silkworm, Bombyx mori, infected with nuclear polyhedrosis virus.

Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that infection of the isolated pupal abdomens of the silkworm, Bombyx mori, with B. mori nuclear polyhedrosis virus (BmNPV) caused generation of a number of polypeptides with a concomitant decrease of cellular polypeptides. These generated polypeptides were not identified as viral structural polypeptides, but were characterized as the degradation products of cellular polypeptides, as evidenced by the reaction with specific antiserum against storage proteins 1 and 2. Immunoblot analysis using anti-BmNPV serum identified at least 14 virus-specific polypeptides in the BmNPV-structural polypeptides of the virus. In vitro translation and subsequent immunoprecipitation with anti-BmNPV serum showed that translation yielded at least 15 polypeptides at the expense of cellular polypeptides. Time-course experiments showed that the viral structural polypeptides and virus-specific translatable mRNAs were not detectable until 3 days postinoculation. On the basis of the fact that the isolated pupal abdomens are in an arrested state of development, the delayed onset of virus-specific macromolecule production in the infected isolated pupal abdomens, as compared with that in the developing intact pupae, implies that some cellular function associated with the pupal-adult development is an important prerequisite for the efficient commencement of BmNPV replication.