Phenotypic data from seminal fluid protein Acp29AB knockdown experiments

Seminal fluid proteins (SFPs) can alter female physiology and behavior,
with consequences that may align with or oppose female interests. Many
SFPs are known to shape aspects of the female post-mating response, yet
evidence for direct effects on female fitness is scarce. In Drosophila
melanogaster, the SFP Acp29AB is firmly linked to sperm defense (P1) and
sperm storage, but its impacts on females are poorly understood. Using a
GAL4–UAS RNAi system with perfectly matched genetic backgrounds, we
manipulated Acp29AB expression either ubiquitously or specifically in the
male accessory gland and then asked how knockdown alters male sperm
competition and, in female mates, oviposition dynamics and competitive
fitness. Both knockdowns impaired male P1, consistent with past work on
Acp29AB. We uncovered a previously undetected effect on oviposition
timing: across 14 days after a single mating, females mated to control
males laid more eggs early in life than females mated to knockdown males,
advancing the timing of reproduction. With accessory gland-specific
knockdown, this shift occurred without a change in total egg output, which
may explain why earlier work focused on totals alone did not detect an
effect. Despite accelerated oviposition in mates of control males,
however, female competitive fitness in a five-day, early-life assay that
included direct (female–female) and indirect (larval) competition did not
differ between treatments. Thus, Acp29AB enhances male P1 and promotes
earlier egg laying in mates, but under our experimental conditions has no
detectable net effect on female fitness. These results broaden the
functional scope of Acp29AB to include female reproductive scheduling and
suggest that some SFPs may evolve rapidly while either being effectively
neutral or having context-dependent effects on female fitness.