Expression of the retrotransposons Surcouf and Blackbeard in the marine diatom Phaeodactylum tricornutum under thermal stress

Transposable elements (TEs) are mobile DNA sequences thought to be involved in the genomic response to environmental stresses of organisms. The thermal stress behaviour of two retrotransposons (Surcouf and Blackbeard) was investigated in the genome of two strains of the marine diatom Phaeodactylum tricornutum. Using quantitative reverse transcriptase polymerase chain reaction, the retrotransposon expression pattern was investigated after thermal stresses and compared with that of the small heat-shock protein (shsp). While the expression of Blackbeard was not affected by temperature changes, the retroelement Surcouf was markedly overexpressed in response to high temperature in correlation with shsp overexpression. An in silico analysis investigated the presence of regulatory heat-inducible motifs such as heat-shock elements, stress response elements and CCAAT boxes within the promoters of shsp and retrotransposons in the genome of P. tricornutum. The results of mRNA quantification are supported by the presence of heat-shock response motifs found in the promoters of shsp and the retrotransposon Surcouf.