The Role of FBti0019985 Transposable Element in Drosophila melanogaster Adaptation: molecular mechanism and functional consequences

Abstract

A way to study environmental adaptation is by elucidating the relationship between mutations and their phenotypic effect. Transposable elements are mobile DNA sequences that can induce genetic variations and have been previously shown to be a considerable source of adaptive mutations in Drosophila melanogaster. FBti0019985 is a putatively adaptive transposable element insertion that is present at higher frequencies in out-of-Africa populations compare to Africa populations, where D. melanogaster was originated. FBti0019985 overlaps 54 nucleotides with the 5'UTR region of CG18446 gene, a gene of unknown function. We found that flies with FBti0019985 insertion are more resistant to cold stress than flies without the insertion. In addition, the presence of FBti0019985 increases the expression levels of CG18446 in normal conditions. Recently, we have found that FBti0019985 has recurrent insertion sites upstream of CG18446. These other insertions are present at lower frequency in natural populations compared to the one previously studied. We found that flies containing these insertions show different patterns of cold resistance compared to flies without the insertion. We are currently performing CRISPR/Cas9 to generate FBti0019985 knockout fly strains to further demonstrate the role of this transposable element in cold stress resistance. Overall, our results indicate that the effect of FBti0019985 depends on the insertion site of this element and provide another example of a transposable element insertion involved in environmental adaptation.