Environmental change and the evolution of genomes: Transposable elements as translators of phenotypic plasticity into genotypic variability

Sergio Pimpinelli and Lucia Piacentini

Phenotypic plasticity is defined as the capacity of a single genotype to exhibit a broad spectrum of phenotypes in response to changing environmental conditions. Such a phenomenon is generally explained as the result of molecular mechanisms (‘epigenetic’ mechanisms) modifying gene expression without altering the underlying DNA sequence. However, the biology of transposable elements, DNA fragments capable of moving themselves from one genomic location to another, suggests that such elements may also induce differential gene expression by affecting regulatory regions. We discuss the ecological and evolutionary relevance of epigenetic modifications vs. transposable elements activity, taking into account that epigenetic modifications are generally reversible but that the modifications induced by transposable elements are stably inherited. In particular we propose a model according to which environmental changes can play multiple roles: the induction of more adapted individual variants via changes in the epigenetic mechanisms that underlie phenotypic plasticity, an increase in genetic variability by the activation of transposable elements, and ‘normal’ selection, i.e. the selection of favourable genetic variants. In other words, faced with drastic environmental stresses, we can imagine immediate processes of adaptation through the production of new phenotypes by epigenetic mechanisms that increase their current survival capacity, followed by genotypic changes that make these phenotypic variants heritable through the germ line. In this view, transposable elements might be considered mediators of phenotypic adaptation and accelerators of evolutionary processes.

Read the paper in full here. This paper is part of the Special Feature: Epigenetics in Ecology and Evolution.

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