Limited impact of the siRNA pathway on transposable element expression in Aedes aegypti

Bergman, A.; Crist, A. B.; Lopez-Maestre, H.; Blanc, H.; Castello-Sanjuan, M.; Frangeul, L.; Varet, H.; Daron, J.; Merkling, S. H.; Saleh, M. C.; Lambrechts, L.

doi:10.1101/2024.11.26.625377

bioRxiv · 10.1101/2024.11.26.625377

Limited impact of the siRNA pathway on transposable element expression in Aedes aegypti

Bergman, A.·Crist, A. B.·Lopez-Maestre, H.·Blanc, H.·Castello-Sanjuan, M.·Frangeul, L.·Varet, H.·Daron, J.·Merkling, S. H.·Saleh, M. C.·Lambrechts, L.

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Abstract

Transposable elements (TEs) are DNA sequences that can change their position within a genome. In the germline of arthropods, post-transcriptional regulation of TE expression is mainly mediated by the Piwi-interacting RNA (piRNA) pathway. piRNAs are small RNAs of 24-30 nucleotides (nt) in length produced from genomic precursor transcripts as well as through a ping-pong amplification cycle. In somatic tissues, certain insects, such as Drosophila, instead rely on the small interfering RNA (siRNA) pathway as a key regulator of TE expression. siRNAs are 21nt small RNAs produced from double-stranded RNA by the endonuclease Dicer2, which guides an RNA-induced silencing complex to degrade a complementary RNA. However, whether the siRNA pathway also regulates TE expression in the mosquito Aedes aegypti, a medically significant vector species with abundant somatic piRNAs, is unknown. To address this question, we investigated the expression of TEs and small RNAs in both somatic and gonadal tissues of a Dicer2 mutant line of Ae. aegypti and its wild-type counterpart. Our results show a modified pattern of TE expression and a decrease in TE-derived 21nt small RNAs in the Dicer2 mutant, but no major shift of TE transcript abundance. The lack of a functional siRNA pathway also causes perturbations in piRNA ping-pong signatures and the expression of certain piRNA-associated genes, but without clear evidence for compensation by increased piRNA pathway activity. We conclude that the mosquito Ae. aegypti produces siRNAs targeting TEs but these lack a critical role in the regulation of TE expression both in somatic and in gonadal tissues.

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Bergman, A., Crist, A. B., Lopez-Maestre, H., Blanc, H., Castello-Sanjuan, M., Frangeul, L., Varet, H., Daron, J., Merkling, S. H., Saleh, M. C., Lambrechts, L.. 2024-11-28. Limited impact of the siRNA pathway on transposable element expression in Aedes aegypti. https://doi.org/10.1101/2024.11.26.625377

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