Identification and characterization of the major Drosophila melanogaster mating plug protein

In many insects, semen coagulates into a mating plug at the distal part of the female's genital tract. Mating plugs have been proposed to facilitate s perm movement or to prevent subsequent matings or sperm loss. The molecular constituents of insect mating plugs have not previously been characterized . Here we report that an abundant autofluorescent protein made by the Droso phila melanogaster male's ejaculatory bulb is a major constituent of the po sterior region of the mating plug. Identities in size, chromosomal location and expression pattern indicate that the autofluorescent protein is FEB-me , an abundant ejaculatory bulb protein reported by Ludwig et al. [Biochem. Genet. 29 (1991) 215]. We cloned and sequenced the RNA encoding this protei n. The transcript, which is male-specific and expressed only in the ejacula tory bulb, encodes a 377 a.a. predicted secreted protein with PGG repeats s imilar to those in homopolymer-forming proteins found in spider silk. (C) 2 001 Elsevier Science Ltd. All rights reserved.