Localization of the 34 kDa polyhedron envelope protein in Spodoptera frugiperda cells infected with Autographa californica nuclear polyhedrosis virus.

Using immuno-electron microscopy the 34 kDa polyhedron envelope (PE) phosphoprotein (pp 34) was localized in cells infected with Autographa californica multiple-nucleocapsid nuclear polyhedrosis virus (AcMNPV). In wild-type AcMNPV-infected cells this protein was found associated with electron-dense "spacers" and the polyhedron envelopes demonstrating their structural relationship. In these cells pp 34 was also found associated with fibrillar structures present in the nucleus and cytoplasm of infected cells. However, when cells were infected with an AcMNPV mutant with an inactivated pp 34 gene, antiserum against pp 34 still localized in fibrillar structures. In cells infected with AcMNPV mutants lacking p 10, and thus devoid of fibrillar structures, pp 34 localized normally with both electron-dense "spacers" and polyhedron envelopes. These data confirm that fibrillar structures are not essential for the morphogenesis of polyhedron envelopes and demonstrate that the association of anti pp 34 serum with these structures is specific but fortuitous.