Evolutionary flux of canonical microRNAs and mirtrons in Drosophila.

Abstract:: Next-generation sequencing technologies generate vast catalogs of short RNA sequences from which to mine microRNAs. However, such data must be vetted to appropriately categorize microRNA precursors and interpret their evolution. A recent study annotated hundreds of microRNAs in three Drosophila species on the basis of singleton reads of heterogeneous length. Our multi-million read datasets indicated that most of these were not substrates of RNAse III cleavage, and comprised many mRNA degradation fragments. We instead identified a distinct and smaller set of novel microRNAs supported by confident cloning signatures, including a high proportion of evolutionarily nascent mirtrons. Our data support a much lower rate in the emergence of lineage-specific microRNAs than previously inferred, with a net flux of ~1 microRNA/million years of Drosophilid evolution.

Authors:: E Berezikov, N Liu, AS Flynt, E Hodges, M Rooks, GJ Hannon, EC Lai

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