Transposable elements modulate gene expression in response to oxidative stress in Drosophila suzukii

Transposable elements (TEs) are major contributors to genomic and regulatory variation and can influence the expression of nearby genes in response to environmental stress. The invasive fruit fly Drosophila suzukii, whose genome is composed of nearly 50% TE-derived sequences, provides an excellent model to investigate the regulatory impact of TEs on stress responses. Although previous studies found no global association between TEs and oxidative stress transcriptomic response in this species, the effects of individual TE insertions remain largely unexplored. Here, we investigated the role of two polymorphic intronic TE insertions, Mrp4-TE and inaE-TE, located within genes implicated in the oxidative stress response in D. melanogaster. Using wild-type strains of D. suzukii, we assessed the effect of these insertions on gene expression following oxidative stress induced by paraquat exposure. We found that their corresponding nearby genes Mrp4 and inaE were upregulated after paraquat treatment and that this response was significantly stronger in flies carrying the corresponding TE insertions. Allele-specific expression analyses further showed that the alleles containing the TE insertions exhibited a tendency towards higher expression levels than alleles lacking the insertions, both under control and oxidative stress conditions, supporting a cis-regulatory effect. In addition, Mrp4-TE was associated with increased sensitivity to oxidative stress. Together, our results provide the first evidence that TE insertions can modulate oxidative stress-responsive gene expression in D. suzukii. These findings highlight the importance of investigating individual TE insertions to understand the genetic and regulatory mechanism underlying stress responses, adaptation, and invasion success in this species.