Seminal proteins but not sperm induce morphological changes in the Drosophila melanogaster female reproductive tract during sperm storage

Abstract

In most insects, sperm transferred by the male to the female during mating are stored within the female reproductive tract for subsequent use in fertilization. In Drosophila melanogaster, male accessory gland proteins (Acps) within the seminal fluid are required for efficient transfer and subsequent accumulation of sperm in the female's sperm storage organs. To determine the events within the female reproductive tract that occur during sperm storage, and the role that Acps and sperm play in these events, we identified morphological changes that take place during sperm storage in females mated to wild-type, Acp-deficient or sperm-deficient males. A reproducible set of morphological changes occurs in a wild-type mating. These were categorized into 10 stereotypic stages. Sperm are not needed for progression through these stages in females, but receipt of Acps is essential for progression beyond the first few stages of morphological changes. Furthermore, females that received small quantities of Acps reached slightly later stages than females that received no Acps. Our results suggest that timely morphological changes in the female reproductive tract, possibly muscular in nature, may be needed for successful sperm storage, and that Acps from the male are needed in order for these changes to occur.

Acp36DE is required for uterine conformational changes in mated Drosophila females

“…In the absence of Acp36DE, female RTs proceeded to stages 1-4 as normal, arriving at the ''hourglass'' shape that is typical of stage-5 uteri (see Fig. 2 A and E) (25). After this stage, RTs of mates of Acp36DE knockdown males did not proceed efficiently, or completely, through the subsequent stages.…”

“…In the later conformational stages, the constriction opens up. The entire uterus takes on an ovoid shape, with sperm ultimately condensing into a single dense, discrete mass that remains just below the openings of the SSOs while the sperm are actively being stored (25). Sperm that are not stored will be Table S1).…”

“…These changes have been hypothesized to assist in sperm movement within the female RT (22)(23)(24)(25). In mammals, small molecules in the seminal plasma, such as prostaglandins, have been implicated in affecting the contractility of female RT tissues (26,27).…”

“…In mammals, small molecules in the seminal plasma, such as prostaglandins, have been implicated in affecting the contractility of female RT tissues (26,27). In D. melanogaster, the receipt of Acps (in aggregate) within the female RT has been shown to induce a reproducible sequence of changes in uterine conformation (25). The nature of female RT contraction would seem to have differing functions with regard to sperm movement in these organisms.…”

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).…”