The Virogenic Stroma in Nuclear and Cytoplasmic Polyhedroses

Abstract

IT has been found recently¹ that in the larval fat body and midgut cells of Lepidoptera and in the midgut cells of Hymenoptera infected with nuclear polyhedroses proteinaceous virogenic stromata form de novo in the nuclear sap. These stromata become increasingly proteinaceous and Feulgen-positive as they grow and develop. Morphologically they are networks, and virus rods differentiate within vesicles in their cords. These begin as fine rodlets about 60 A. × 1200 A. in size and increase in situ to their final size of 280 A. × 2800 A. They are then set free from their vesicles into the pores of the net by disruption of the surrounding cord material and may ultimately reach the ring zone between the centrally placed virogenic mass and the nuclear membrane. The freed virus rods become enveloped by independently formed and still-growing capsule membranes, within which capsule protein is deposited. The encapsulated rods then become occluded within crystalline protein polyhedra, which arise and grow in the ring zone and later in the enlarged pores of the late-stage infected nucleus.