During their lives, insects go through different phases that are very different from each other in morphological and physiological terms. An example is the differences between a caterpillar and a butterfly in the same species of lepidoptera.

Until recently, it was thought that   hormones, transduction transcription factors for the effect of these hormones and effector genes in the insects’ metamorphosis, and their expression determined young or adult characteristics.

A study by Xavier Bellés and Eva Gómez, director and researcher at the Evolutionary Biology Institute (UPF-CSIC), respectively, which has been published in the online edition of the Proceedings of the National Academy of Sciences (PNAS) describes a new level of regulation in insects’ metamorphosis, involving MicroRNAs.

MicroRNAs have a leading role in the regulation of metamorphosis

Xavier Bellés said that “the work we have published in the PNAS describes how microRNAs, which are RNAs of approximately twenty two nucleotides with a modulative function (normally as a repressor) of the translation of messenger RNAs, play a leading role in the regulation of insects’ metamorphosis”.

Using the technique of RNA interference and working with the woodlouse species Blatella Germanica, researchers at the IBE silenced the expression of the dicer enzyme, which is essential in the formation process of microRNAs from its precedents.

By silencing the expression of dicer in the last nymph phase, normal production of microRNAs was prevented and instead of mutating intos adult as the controls did, the experimental insects mutated into an additional nymph phase. This clearly shows that microRNAs are essential for the metamorphosis to take place properly.

The hypothesis inferred from these experiments is that during the the mutation into an adult, some microRNAs could repress the gene expression that gives nymph characteristics, so that the adult genetic programme emerges without any errors.

Xavier Bellés’ team is now considering how to identify the specific microRNAs involved in metamorphosis regulation and what genes these microRNAs act upon.

The Evolutionary Biology Institute

The Evolutionary Biology Institute (IBE) was created in July 2008, as a result of an agreement between Pompeu Fabra University and the Higher Council for Scientific Research (CSIC). It is a mixed center located in Barcelona and its work focuses on research into evolutionary biology and biodiversity.

 

The IBE is currently located in provisional offices and the construction of a new plant by the CSIC on the Ciutadella Campus of UPF is planned for the future, on land provided by the University. This work is scheduled for completion in 2011. The future location of the IBE will be very close to the Mar Campus of UPF, which contains the Barcelona Biomedical Research Park (PRBB).

Reference works :

Xavier Bellés, X. & Eva Gómez-Orte. " MicroRNA-dependent metamorphosis in hemimetabolan insects",  PNAS , 4 de desembre de 2009, doi: 10.1073/pnas.0907391106.