[microRNAs: regulators of metamorphosis in insects]

In the animal kingdom, metamorphosis is a well-known developmental transition within various taxa (Cnidarians, Echinoderms, Molluscs, Arthropods, Vertebrates, etc.), which is characterized by the switching from a larval stage to an adult form through the induction of morpho-anatomical, physiological, behavioral, and/or ecological changes. Over the last decades, numerous studies have focused on the hormonal control of cellular processes underlying metamorphosis. Recently, another regulatory network has emerged trough the discovery of microRNAs, non-coding RNAs of 19 to 25 nucleotides that are highly conserved among taxa and act by modulating gene expression at the post-transcriptional level. Experiments carried out on model insects highlighted the relevance of microRNAs in several developmental processes during metamorphosis. This review aims to give an overview of the regulatory actions of microRNAs in the programming of cellular and molecular events associated with the metamorphosis of insects and also to provide new insights into the evolutionary history of this taxon.