Abstract
microRNAs (miRNAs) are important regulators of animal development and other processes, and impart robustness to living systems through post-transcriptional regulation of specific mRNA transcripts. It is postulated that newly emergent miRNAs are generally expressed at low levels and with spatiotemporally restricted expression domains, thus minimising effects of spurious targeting on animal transcriptomes. Here we present ovarian miRNA transcriptome data for two geographically distinct populations of the Speckled Wood butterfly (Pararge aegeria). A total of 74 miRNAs were identified, including 11 newly discovered and evolutionarily-young miRNAs, bringing the total of miRNA genes known from P. aegeria up to 150. We find a positive correlation between miRNA age and expression level. A common set of 55 miRNAs are expressed in both populations. From this set, we identify seven that are consistently either ovary-specific or highly upregulated in ovaries relative to other tissues. This ‘ovary set’ includes miRNAs with known contributions to ovarian function in other insect species with similar ovaries and mode of oogenesis, including miR-989 and miR-2763, plus new candidates for ovarian function. We also note that conserved miRNAs are overrepresented in the ovary relative to the whole body.
Highlights
MicroRNAs are short regulatory RNAs with important roles in post-transcriptional regulation [1]
We constructed and sequenced small RNA libraries from ovaries of the Speckled Wood butterfly P. aegeria to identify miRNAs expressed in the lepidopteran ovary
After filtering reads to remove possible degradation products and non-miRNAs, these were compared to a published dataset of P. aegeria miRNAs [15]
Summary
MicroRNAs (miRNAs) are short regulatory RNAs with important roles in post-transcriptional regulation [1]. They are of significance at all stages during an animal’s life cycle from embryonic development [2,3,4,5] to post-embryonic development [6,7] and reproduction [5,8]. Understanding the evolution of miRNAs is important to understanding the evolution of growth, reproduction and development. It has been postulated that newly emergent animal miRNAs are generally expressed at low levels and with spatiotemporally restricted expression domains [9,10]. A PLOS ONE | DOI:10.1371/journal.pone.0142243 November 10, 2015
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