Drosophila males transfer antibacterial proteins from their accessory gland and ejaculatory duct to their mates

The male fruitfly, Drosophila melanogaster, transfers to his mate proteins that increase his reproductive success by causing changes in her behavior a nd physiology. Here we show that among the transferred proteins are ones wi th antibacterial activity. We performed Escherichia coli overlay assays of native PAGE or renatured SDS-PAGE of reproductive tissue extracts of wild-t ype or transgenic males deficient in accessory gland function. We detected a 28 kDa male accessory gland-derived protein and two ejaculatory duct-deri ved proteins all with antibacterial activity. Based on its gel mobility and tissue of synthesis, one of the ejaculatory duct proteins is likely to be andropin, a previously-reported 6 kDa antibacterial peptide. All three prot eins are transferred to females during mating. Therefore, they could assist in protecting the male's reproductive tract and, after transfer to the fem ale, the female's reproductive tract or eggs against bacterial infection. S ince seminal fluid proteins are transferred before the sperm, these antibac terial proteins may also protect sperm from bacterial infection. (C) 2001 E lsevier Science Ltd. All rights reserved.