Consequences of polydnavirus infection on circulating trehalose in the soybean looper, Pseudoplusia includens

Trehalose (α-D-glucopyranosyl-α-D-glucopyranoside) is a disaccharide that is the most abundant circulating hemolymph sugar. Trehalose is hydrolyzed into two glucose molecules by the enzyme trehalase. There are two forms of trehalase:  soluble and membrane bound. Both are found in the soybean looper, Pseudoplusia includens. The soybean looper is parasitized by the parasitoid wasp Microplitis demolitor in the family Braconidae. M. demolitor has a symbiotic virus integrated into its genome. The M. demolitor bracovirus (MdBV) is a polydnavirus that does not replicate in the soybean looper. Virions are found in mature ovaries of the parasitoid wasp in the calyx fluid. 0.1 to 0.01 equivalents of calyx fluid are injected with the egg during parasitism. Total sugar concentrations in the hemolymph were carried out using glucose oxidase activity with porcine kidney trehalase. Trehalose concentrations were obtained by subtracting circulating glucose from total sugar. Trehalase activity in the tissues was determined by glucose oxidase assays to determine the glucose produced. Control larvae were compared to infected larvae, which were injected with filtered calyx fluid. During infection, trehalose titres and trehalase activity increase during MdBV infection. This increase in trehalose may be beneficial to the parasitoid larvae by adding additional nutrition as well as maintaining homeostasis by increasing host larvae resistance to desiccation and temperature stress.