MOSAIC INFECTION WITH A DENSONUCLEOSIS VIRUS IN THE MIDGUT EPITHELIUM OF THE SILKWORM, BOMBYX-MORI

Initially, we showed that the hereditary mosaic strain (mo), marked with the mosaicism of larval skin markings of the silkworm, Bombyx mori, possessed the dominant gene (Nid-1), which controls the nonsusceptibility to the densonucleosis virus type-1 (DNV-1). Skin mosaic larvae, obtained in the F3 generation from crossing the mo strain and a normal strain with the susceptible gene (+Nid-1), were administered DNV-1. By means of immunoperoxidase staining of the larval body section, three larvae were found with midgut mosaicism in two areas, infected (+Nid-1/+Nid-1) and noninfected (Nid-1/+Nid-1). Histological sections of the mosaic midgut revealed, in the infected area, increased numbers of degraded columnar cells which had accumulated in the epithelium and had become attached to intact goblet cells. In the noninfected area, the epithelium had a large number of tightly arranged columnar cells with a few goblet cells among them. The large number of columnar cells produced in the noninfected epithelium may result from the deficient function of degraded columnar cells in the infected area of the epithelium and result in the prolongation of the DNV infection in the larva with midgut mosaicism. © 1990.