Expression of Mst89B and CG31287 is needed for effective sperm storage and egg fertilization in Drosophila

In Drosophila, male reproductive fitness can be affected by any number of
processes, ranging from development of gametes, transfer to and storage of
mature sperm within the female sperm storage organs, and utilization of
sperm for fertilization. We have previously identified the 89B cytogenetic
map position of D. melanogaster as a hub for genes that effect male
paternity success when disturbed. Here, we used RNA interference to test
11 genes that are highly expressed in the testes and located within the
89B region for their role in sperm competition and male fecundity when
their expression is perturbed. Testes-specific knockdown (KD) of bor and
CSN5 resulted in complete sterility, whereas KD of CG31287, Manf and
Mst89B, showed a breakdown in sperm competitive success when second to
mate (P2 < 0.5) and reduced fecundity in single matings. The low
fecundity of Manf KD is explained by a significant reduction in the amount
of mature sperm produced. KD of Mst89B and CG31287 does not affect sperm
production, sperm transfer into the female bursa or storage within 30 min
after mating. Instead, a significant reduction of sperm in female storage
is observed 24 h after mating. Egg hatchability 24 h after mating is also
drasti-cally reduced for females mated to Mst89B or CG31287 KD males, and
this reduction parallels the decrease in fecundity. We show that normal
germ-line expression of Mst89B and CG31287 is needed for effective sperm
usage and egg fertilization.