BmNPV alters NADP-dependent malate dehydrogenase activity and associated macromolecules and retards growth and development of the mulberry silkworm,Bombyx moriL., during the final instar

Abstract

Changes in tissue-specific NADP-dependent malate dehydrogenase (MDH) activity and protein and cholesterol contents and retardation of growth and development in the mulberry silkworm, Bombyx mori L., induced by infection with a baculovirus, the B. mori nucleopolyhedrovirus (BmNPV), were investigated. The study revealed that the relative growth rate and development of the fifth-instar larva was significantly inhibited during the progression of nuclear polyhedrosis disease at various times post inoculation (p.i.). Percent pupation and reproductive output were also adversely affected. NADP-dependent MDH activity in the hemolymph peaked sharply at 6 h p.i. and then gradually decreased, reaching a minimum at 264 h p.i., with exceptions at 30 and 72 h p.i. These levels of MDH activity were different from those in non-infected controls. In fat-body tissues, NADP-dependent MDH activity was significantly higher in infected insects than in non-infected controls of the same age. These results indicate that baculovirus infection causes significant changes in intermediary metabolic pathways, causing a significant fall and rise in protein and cholesterol contents in tissues during development of fifth-instar larvae.