Dl. Coxfoster et Je. Stehr, INDUCTION AND LOCALIZATION OF FAD-GLUCOSE DEHYDROGENASE (GLD) DURING ENCAPSULATION OF ABIOTIC IMPLANTS IN MANDUCA-SEXTA LARVAE, Journal of insect physiology, 40(3), 1994, pp. 235-249
FAD-Glucose dehydrogenase (GLD) (EC 1.1.99.10) was assayed during the
encapsulation response against abiotic implants (sterile latex) in fou
rth instar Manduca sexta larvae. No GLD activity was detected in fresh
hemolymph or hemocytes of control or sham-treated larvae. Two types o
f responses occurred at 0.5 and 3h after implantation. In the majority
of larvae, only the encapsulation had high levels of GLD specific act
ivity. In the second response, low levels of GLD specific activity wer
e detected in hemocytes and cell-free hemolymph but not in the encapsu
lation. By 24h after implantation, GLD activity was detected in the en
capsulation tissue of all larvae. Levels of GLD specific activity did
not significantly differ over time (0.5-72 h) during encapsulation. Fr
eezing cell-free hemolymph from control larvae activated otherwise ina
ctive hemolymph stores of GLD. In vitro experiments and histochemical
staining demonstrated that GLD activity was localized in granules of p
lasmatocytes adhered to coverslips. Granules of both plasmatocytes and
granulocytes contained GLD protein as detected by immunohistochemistr
y. Based on previous characterization of GLD, we hypothesize that GLD
participates in strengthening the encapsulation and in the killing rea
ction, via reaction with quinones generated by phenoloxidase and subse
quent production of free radicals.