BioProject

The presence of small RNAs in sperm is a relatively recent discovery and little is currently known about their importance and functions. More...

The presence of small RNAs in sperm is a relatively recent discovery and little is currently known about their importance and functions. Some sperm RNAs play a putative role in the epigenetic inheritance of paternally acquired traits, whereas others have been shown to be important at fertilisation and during embryo development. Environmental changes such as social conditions and dietary manipulations are known to affect the composition and expression of some small RNAs in sperm. Changes in environmental conditions are thought to elicit a physiological stress response which may affect the germline and result in an associated change in gamete miRNA profiles. Here, we tested how microRNA profiles in sperm are affected by variation in both sexual selection and dietary regimes, using flies drawn from Drosophila melanogaster fruit fly selection lines. The selection lines were exposed to standard versus low yeast diet treatments and three different sex ratio treatments varying in population sex ratio (male-biased, female-biased or equal sex) in a full-factorial design. After 38 generations of selection, we collected sperm samples from males in all selection lines. Prior to sampling, all males were maintained on their selected diet and exposed to a common garden male-only environment for five days to standardise sperm expenditure. We performed transcriptome analyses on miRNAs in purified sperm samples. Overall, we found that sperm contained about 25% of all miRNAs currently described in Drosophila. The diversity of miRNAs was not significantly different in any of the selection regimes. However, we found 11 miRNAs that were differentially expressed according to sex ratio treatment, with the majority showing differences between male- and female-biased lines. Dietary treatment per se had no significant effect on miRNA expression levels, but did show interactions with sex ratio. Our findings suggest that long-term adaptation may affect miRNA profiles in sperm possibly via a varied response to immediate short-term changes in the environment. Less...