Site of viral RNA synthesis within the midgut cells of the silkworm, Bombyx mori, infected with cytoplasmic-polyhedrosis virus
J Invertebr Pathol 9(4): 480-487
The pattern of nucleic acid synthetic activity within the midgut cells of healthy larvae of the silkworm, B. mori, and of larvae infected with the cytoplasmic-polyhedrosis virus was demonstrated by means of autoradiography with labeled nucleic acid precursors. Five hours after injection of uridine-H3, the healthy cells generally incorporated the labeled material into cytoplasmic RNA and partly into nucleic RNA, whereas the diseased cells on the 2nd to the 5th day after virus inoculation incorporated much of the labeled uridine into nucleic RNA and some into cytoplasmic RNA. In the nuclei of virus-infected cells, the nucleic label appeared most densely over the nucleoli. Thus the distinct difference in the uptake of the RNA precursor between the healthy and infected cells indicated that the nu-cleolus of the infected cell may be a site of the viral RNA synthesis. Autoradiograms with thymidine-H3 revealed no essential difference in the pattern of DNA synthesis between healthy and diseased midguts, and only a few cells incorporated the labeled material into their nuclei. At the late stage of virus infection, however, when some infected mid- gut cells eventually degenerated, there was a slight increase in the nucleic label in the newly generated cells.