The polyhedrin of insect baculovirus

a polypeptide aggregated in infected cells was studied by means of immunoelectron microscopy. A protein A-gold technique of immunomarking and localizing the polyhedron protein of the nuclear polyhedrosis virus of cotton leafworm Spodoptera litura (SINPV) was successfully applied to ultrathin sections of larvae from different stages postinfection (p. i.) per os. The results showed that: (1) At 36 hours p. i. near the place of the endoplasmic reticulum immunogold particles were heavy but in the nucleus label was light. (2) The polyhedrin moving into the nucleus and those partially assembled polyhedra became labelled at 48 hours p. i. But the network (known as virogenic stroma) and the incomplete nucleolus present in the same cells at that stage were not labeled. (3) Most polyhedra became fully developed at 72 to 96 hours p. i. and were seen to be surrounded by a polyhedral membrane. There was almost no polyhedrin labeled out of the mature polyhedra. This technique is helpful for us to understand the synthesis

distribution and migration process of baculovirus polyhdrin in infected tissue and cells at the electron microscope level.