Expression of retrotransposon-like sequences in Scots pine (Pinus sylvestris) in response to heat stress

Mobile genetic elements, or transposable elements, are ubiquitous components of plant genomes, and in pine these sequences have been estimated to comprise up to 70 % of the genome. Retrotransposon activity can be a major factor in genome instability, rearrangements and therefore also plasticity of the genome and adaptation to changing environmental conditions. Plant retrotransposons have been shown to be activated under stress conditions. In our study we demonstrate transcriptional activation of many non-specific retrotransposon-like sequences in Scots pine (Pinus sylvestris) after exposure to heat stress. Active retrotransposons have not been described in gymnosperms, one of the most ancient plant groups. Our results suggest the existence of several groups of active retrotransposons in the Scots pine genome, which share different levels of similarity with known retro-elements from other plant species. Further studies of retrotransposon activation in pine are needed to increase understanding of their possible function and evolution.