The Drosophila seminal fluid protein Acp26Aa stimulates release of oocytes by the ovary

Abstract

Mating stimulates the rate of egg-laying by female insects. In Drosophila melanogaster this stimulation is initially caused by seminal fluid molecules transferred from the male (Acps or accessory gland proteins; reviewed in [1] [2] [3]). Egg-laying is a multi-step process. It begins with oocyte release by the ovaries, followed by egg movement down the oviducts and the deposition of eggs onto the substratum. Although two Acps are known to stimulate egg-laying [4] [5], they were detected by assays that do not discriminate between the steps of this process or allow examination of its earliest changes [4] [5] [6] [7]. To determine how egg-laying is regulated, we developed a generally applicable assay to separate the process into quantifiable steps, allowing us to assess the ovulation pattern and rate of egg movement. As the steps are interdependent yet potentially subject to independent controls, we determined the contribution of each step and effector independent of the others. We used a statistical method [8] [9] that separately considers and quantifies each 'path' to a common end. We found that the prohormone-like molecule Acp26Aa [5] [10] stimulates the first step in egg-laying - release of oocytes by the ovary. During mating, Acp26Aa begins to accumulate at the base of the ovaries, a position consistent with action on the ovarian musculature to mediate oocyte release. Understanding how individual Acps regulate egg-laying in fruitflies will help provide a full molecular picture of insects' prodigious fertility, of reproductive hormones, and of the roles of these rapidly evolving proteins [11] [12].

Sex peptide of Drosophila melanogaster males is a global regulator of reproductive processes in females

“…We assayed mRNAs regulated by SP at 3 and 6 h after mating, to coincide with phenotypic responses observed at 3 h [20,21,23,[33][34][35] and through 6 h and beyond [14,20]. We conducted fourfold independent biological replication.…”

Genetics and genomics of Drosophila mating behavior

“…The female can accept the male or reject him by moving away. Successful copulation is accompanied by the transfer of sperm and seminal fluids that stimulate the release of oocytes by the ovary (6) and reduce female receptivity to other males (7,8). Components of the seminal fluids are associated with the reduced lifespan of mated females (9), setting up an intersexual conflict (10).…”

The consequences of genetic variation in sex peptide expression levels for egg laying and retention in females

“…In this species, over 138 seminal proteins and peptides are transferred (along with sperm) to females during mating (Avila et al, 2011). These seminal fluid components are important for male and female fitness and, among other functions, they facilitate successful sperm storage (Adams and Wolfner, 2007), influence the outcome of sperm competition (Begun et al, 2000;Chapman et al, 2001), reduce female receptivity (Chapman et al, 2003;Liu and Kubli, 2003) and stimulate ovulation (Heifetz et al, 2000;Chapman et al, 2001).…”

“…We also found no correlation between SP retention and the number of eggs laid by that male's mate after mating. This may be due to effects of other seminal fluid proteins (for example, ovulin, (Heifetz et al, 2000), CG33943 (Ravi Ram and Wolfner, 2007)) that also contribute to the maleinduced effects on egg laying. The fact that refractory period duration if correlated with SP expression levels but that egg laying is not suggests that these two female responses to SP are at least partially uncoupled.…”