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Hormonal regulation of insect metamorphosis
Xavier Bellés, Director of the Insitute of Evolutionary Biology has published an invited review for non-specialists. After 36 years of studying insect metamorphosis (his first paper on the activity of juvenile hormone on metamorphosis appeared in 1979 in a no-SCI journal), Investigacion y Ciencia considered that this kind of research might be interesting for their readers. He was asked to focus on their work on the contribution of miRNAs to metamorphosis, but he preferred to offer a wider overview.
In the review he explains that insect metamorphosis is basically regulated by two hormones: ecdysone and juvenile hormone, and a set of transcription factors, the most important of which, by the moment, are Met, Kr-h1, BR-C and E93. Essentially, ecdysone and an unknown metamorphosis competence factor induce the expression of E93, which trigger metamorphosis (this happens when the insect has a minimal critical size). However, in juvenile stages, when the insect has not yet achieved this size, juvenile hormone, transduced by Met and Kr-h1, prevents the expression of E93, and metamorphosis does not proceed. Apparently quite simple, but there are many details that complicate the mechanisms.
Reference Article: Bellés X (2015). Regulación hormonal de la metamorfosis en los insectos. Investigación y Ciencia