eLife assessment
This important study describes an atypical role of the odorant binding protein Obp56g in mating plug formation in Drosophila melanogaster suggesting that Obps may play roles in reproduction in addition to their originally described roles in olfaction. Mutant males lacking Obp56g fail to induce the formation of a mating plug in the female reproductive tract-leading to ejaculate loss and reduced sperm storage. The evidence supporting the claims of the authors is solid and compelling. The work will be of interest to biologists studying Obps and seminal fluid protein function and their evolution.