Upregulation of antioxidant genes in the spermathecae of honey bee (Apis mellifera) queens after mating

During storage, the viability of sperm in a honey bee (Apis mellifera) queen’s spermatheca can be decreased by reactive oxygen species. We hypothesized that the expression of antioxidant genes would increase in queen spermathecae after mating. We measured queen morphometric characteristics and expression levels of seven antioxidant-encoding genes in virgin and mated queen spermathecae. We identified a 12% increase in body weight and a fourfold increase in ovary weight in mated queens. There was a twofold higher expression of catalase, thioredoxin 2, and thioredoxin reductase 1 in the spermathecae of mated vs. virgin queens. Expression of the other antioxidant genes (glutathione S-transferase D1, superoxide dismutase 1, vitellogenin, and glyoxalase domain-containing 4-like (GLOD4L) in spermathecae was not different between mated and virgin queens. In drone semen, expression of antioxidant genes was overall low compared to queens except for GLOD4L, which was equivalent to that in queen spermathecae. Increased expression of antioxidant genes may assist in maintaining sperm viability inside the spermathecae of mated queens.