Identifying Venom Gland Components of the Ectoparasitoid Wasp, Anisopteromalus calandrae

Females of the ectoparasitoid wasp Anisopteromalus calandrae seek larvae within a corn or wheat kernel, drill into it with their ovipositor, inject a venom cocktail that paralyzes and suppresses host development, and deposit an egg. The parasitoid larvae emerge and feed on the host larva.  Because of the potential to reduce pest populations, A. caladrae is used as a biological control agent of some stored product insects.  However, components of the venom that explain the mechanism by which the female wasp paralyzes and suppresses development of the host are unknown. We used transcriptome sequencing of the wasp venom gland and associated tissues to identify venom and related transcripts. The majority of hits by BLAST were to Nasonia vitripennis as well as other bees, wasps, and ants. Gene ontology grouped sequences into eleven molecular functions, among which binding and catalytic activity were over represented. Thirty-nine transcripts were homologous to those in N. vitripennis venom, including metalloproteinases and dipeptidyl peptidase IV.  Metalloproteinases were the most abundant transcript in the A. calandrae venom gland transcriptome; in venomous snakes, metalloproteinases interfere with blood coagulation and break down the extracellular matrix of their victims. Dipeptidyl peptidase IV is a serine peptidase that activates promelittin, the main constituent of honeybee venom; melittin activates phospholipase 2 and disrupts cellular membranes. Other components included acid phosphatases, endonucleases, proteases, inhibitors, venom protein precursors, and cytochrome oxidases. This work is the first to characterize the venom of A. calandrae and could lead to interesting alternatives in pest control and management.