Origin of new miRNAs at different evolutionary periods.

<p>The divergence time of the phylogeny is based on the <i>Drosophila</i> 12 Genomes <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004096#pgen.1004096-Clark1" target="_blank">[27]</a>, Gaunt <i>et al.. </i><a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004096#pgen.1004096-Gaunt1" target="_blank">[65]</a> and Bolshakov <i>et al.. </i><a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004096#pgen.1004096-Bolshakov1" target="_blank">[66]</a>. The number of highly expressed, canonical miRNAs that are inferred to originate in each time interval is given on the corresponding branch. Species abbreviations: <i>D. mel</i>, <i>D. melanogaster</i>; <i>D. sim</i>, <i>D. simulans</i>; <i>D. pse</i>, <i>D. pseudoobscura</i>; <i>D. vir</i>, <i>D. virilis</i>. The 12 miRNAs of the last 4 Myrs are miR-979 and miR-4966 from the miR-972s cluster, miR-983-2 and miR-984 from the miR-982s cluster, miR-954, miR-956, miR-971, miR-985, miR-990, miR-997, miR-1017 and miR-2279. The ten miRNAs emerged between 4 and 30 Myrs ago are miR-972, miR-978 and miR-2499 from the miR-972s cluster, miR-303, miR-982 and miR-983-1 from the miR-982s cluster, miR-992 and miR-2498 from the miR-310s cluster, miR-1001 and miR-2494.