Elucidating the role of artificial diet on protease enzyme activity in larval midgut of Helicoverpa armigera as influenced by modification of artificial diet by Cry1Ac toxin

Digestive midgut protease activity in fifth instar larvae (L₅) of Helicoverpa armigera was investigated under controlled conditions, where, an artificial diet containing different concentrations (0.005 µg/g - 0.3 µg/g) of Cry1Ac (Crystalline ä-endotoxin from class A, subclass c) toxin was fed. Here, the Bacillus thuringiensis (Bt) cotton seeds were used as Cry1Ac toxin source that was determined using Envirologix ELISA (Enzyme Linked Immunosorbent Assay) kit. The results showed an increase in the general midgut proteases as well as specific proteases activity linked to enzymes such as trypsin-, chymotrypsin-, elastase-, and leucine aminopeptidase-like with the increasing toxin content of the diet. However, carboxypeptidase-A and carboxypeptidase-B protease activity remained unaltered as a consequence of the incorporation of Cry1Ac toxin in the diet, which is also reported to be absent in midgut of H. armigera as evident in the control group.