Drosophila melanogaster Sex-Peptide is the molecular basis of the sperm effec. H. Liu ¹, J. Peng ¹, S. Buesser ¹, D. Egli ², E. Kubli ¹. 1) Institute of Zoology, University of Zurich, Zurich, Switzerland; 2) Institute of Molecular Biology, Univeristy of Zurich, Zurich, Switzerland.

   In Drosophila Melanogaster, mating leads to two characteristic behavioral responses in females, increased egg laying and reduction of receptivity. Both post mating responses persist for a few days. Seminal fluid and sperm are involved in these responses. Males that do not transfer sperm can induce these responses for only about one day. Manning (Nature 194, 252-253, 1962) suggested that sperm is responsible for the long-term response (= sperm effect). Sex-Peptide (SP) and DUP99B, two small peptides of the Sex-peptide pheromone family, can induce these two post mating responses for one day when injected into virgin females. To study the role of the two peptides in a normal mating, we tried to knock them out separately. We produced a SP null mutant with the homologous recombination targeting technique developed by Rong and Golic (Science 288, 2013-2018, 2000). We found that in matings with wild type females, this mutant only induces a slight increase of egg laying on the first day (likely elicited by Ovulin and DUP99B which are still transferred). Reduction of receptivity persists only for one to two days. We also found that SP does not affect sperm transfer and storage. Sperm can be stored in the female for a long time due to the low egg laying rate after copulation with SP null males. However, we could not find any changes in the females post mating responses after a copulation with a Dup99B null mutant male. We conclude that DUP99B has only a minor effect in eliciting the post mating responses. In another study, we showed (see poster by Peng et al.) that SP binds to sperm with its N-terminal part. In sum, we conclude that SP is the major factor inducing the post mating responses in D. melanogaster females.