TITLE:
Phenoloxidase and Melanization Innate Immune Activities in Green Darner Dragonfly Nymphs (Anax junius)
AUTHORS:
Mark Merchant, Matthew R. McClure
KEYWORDS:
Aquatic Insects, Arthropod, Dragonfly, Hemolymph, Innate Immunity, Insect
JOURNAL NAME:
Advances in Biological Chemistry,
Vol.12 No.4,
August
30,
2022
ABSTRACT: Insects in the Order Odonata are highly subject to
infection by gregarine parasites. However,
despite the important ecological roles that insects play in every ecosystem in which they exist, little
research has been devoted to the description of insect immunity. Insects rely
heavily on the rapid actions of innate immune mechanisms to prevent
infection. We characterized the melanization response in the hemolymph of green
darner dragonfly (Anax junius) nymphs. Incubation of chymotrypsin-activated
hemolymph with L-DOPA resulted in
volume- and time-dependent production of dopaquinone via the phenoloxidase (PO) enzyme, with biphasic accumulation of product. The PO activity was temperature-dependent, with a stepwise
increase from 20℃ - 35℃ and maximum activity measured at 35℃ - 40℃. The
formation of product was also inhibited in a concentration-dependent
manner by diethylcarbonate, a specific
inhibitor of PO activity, which indicated that the observed activity was
due to the presence of PO enzyme. The rate of formation and quantity of melanin
was dependent on exposure to different titers of bacteria. This is the first characterization of both PO
activity and melanization response in green darner dragonflies.