Stress and transposable elements: co-evolution or useful parasites?

Abstract

The activity of transposable elements can be induced by environmental and population factors and in particular by stresses in various organisms. A consequence of the increase in transposable element mobility is the creation of new genetic variability that can be useful in the face of stressful conditions. In this review, results supporting this hypothesis are presented and discussed. The main question is how stress induces the activity of transposable elements. We discuss hypotheses based upon the existence of promoters or ®xation sites of transcription activators in the untranslated regions of transposable elements, similar to those found in regulatory regions of host defence genes.

The mariner transposable element in natural populations of Drosophila simulans

“…So a second explanation could be that migrants that face new and stressful environments show a deregulation of the activity of the mariner elements and other TEs, leading to genome instability (Capy et al, 2000). This instability may produce genetic variation and novelties from which new genetic combinations could be selected and adaptive (Biémont et al, 1997;Vieira et al, 1999).…”

Transposable elements as genomic diseases

“…The time resolution of molecular clocks is limited by the time needed to accumulate a single (synonymous) nucleotide substitution, the elementary time unit of molecular evolution. For E. coli in the wild, for example, synonymous nucleotide substitutions accumulate at a rate of circa K s =0.009 per gene pair and per 10 8 -3×10 8 generations 50 . For a transposable element of approximately 1 kilo basepair in length, one would expect of the order of 9 substitutions in this amount of time.…”

The biology and potential for genetic research of transposable elements in filamentous fungi

“…Regulatory pathways controlled by the host and transposons act on the regulation of the transposition. In animals and plants, transposon control has been shown at different levels, revealing that these elements are generally quiescent during growth and development, but can be activated by stress (Capy et al, 2000;Grandbastien, 1998;Wessler, 1996). Little is known about the mechanisms that control the activity of transposable elements in fungi, although recent evidence shows that they can be activated by stress and silenced by epigenetic processes.…”

“…Several transposons in plants, yeasts and Drosophila show activity under conditions of abiotic (irradiation, temperature, oxidative stress) or biotic (tissue culture, infection by pathogens or protoplast isolation) stress (Capy et al, 2000;Grandbastien, 1998;Wessler, 1996). Some of the factors that stimulate transposition have been tested on fungi, e.g.…”