Glucose dehydrogenase is required for normal sperm storage and utilization in female Drosophila melanogaster

Female sperm storage is a key factor for reproductive success in a variety of organisms, including Drosophila melanogaster. The spermathecae, one of the Drosophila sperm storage organs, has been suggested as a long-term storage organ because its secreted substances may enhance the quality of sperm storage. Glucose dehydrogenase (GLD) is widely expressed and secreted in the spermathecal ducts among species of the genus Drosophila. This highly conserved expression pattern suggests that this enzyme might have an important role in female fertility. Here, we examine the function of GLD in sperm storage and utilization using Gld-null mutant females. The absence of GLD reduced the amount of sperm stored in the spermathecae and led to a highly asymmetrical sperm distribution in the two spermathecal capsules of the mutant females. The storage defect was especially severe when the mutant females were crossed to a Gld-mutant male that had previously mated a few hours before the experimental cross. Under this mating condition, the mutant females stored in the spermathecae only one-third of the sperm amount of the wild-type control females. In addition, the mutant females used stored sperm at a slower rate over a longer period compared with wild-type females. Thus, our results indicate that GLD facilitates both sperm uptake and release through the spermathecal ducts.