Affiliations: 1) Cornell University; 2) National Heart Lung and Blood Institute, NIH, Bethesda, MD
Keywords: r. other (seminal fluid proteins); r. other (sperm)
Seminal fluid proteins (SFPs) induce a myriad of physiological and behavioral changes in mated female flies that are needed for efficient fertility. These post-mating changes last for ~10-14 days, because some male-derived seminal proteins (LTR-SFPs) “prime” sperm to bind the seminal Sex Peptide (SP). This allows SP to persist in the female and modulate post mating responses long-term. All factors currently known to account for binding of SP to sperm within the female reproductive tract are male derived. We wished to know whether female factors (protein/non-protein) also play roles in associating SP with sperm. We found that sperm in ejaculate bind SP much more weakly than sperm within females, suggesting that priming of sperm improves inside the female reproductive tract. Moreover, SP binding to sperm increases with time or transit within the female reproductive tract. Interestingly, while some LTR-Sfps also bind to sperm, the effects of female factors on the timing of their (transient) sperm-binding differ. This, in turn, suggests that female molecules participate in facilitating SP’s and other SFPs’ binding to sperm. Ablation of the female’s spermathecal secretory cells (SSCs), or mutation of Hr39, which leads to defective SSCs and/or parovaria, did not affect SP’s initial binding to sperm, although Hr39 mutant females retained more sperm and SP long-term.