Hormonal regulation of microRNA expression dynamics in the gut of the yellow fever mosquito Aedes aegypti

The yellow fever mosquito Aedes aegypti is an obligatory blood feeder and a major arboviral disease vector, evoking severe public health concerns worldwide. In adult female mosquitoes, the gut is critical for blood digestion and pathogen entry. We aimed for a systematic exploration of microRNA expression dynamics in the gut during the gonadotrophic cycle. Small RNA libraries were constructed from female mosquito gut tissues at five time points. Unsupervised hierarchical clustering revealed three expression clusters (early, mid and late) peaking at sequential time points - 24, 48 and 72 h posteclosion. Differentially expressed miRNAs were identified at 24 h post-blood meal (PBM). Depletions of Methoprene-tolerant [Met; the juvenile hormone (JH) receptor] and Ecdysone receptor [EcR; the receptor to 20-hydroxyecdysone (20E)] were performed using dsRNA to these genes to investigate impacts on microRNA expressions. Our results suggest that Met-mediated signalling downregulates miRNA expression from the early cluster and upregulates that from the late cluster. EcR signalling either up- or downregulated miRNA levels at 24 h PBM, indicating a differential effect of this receptor in miRNA gene expression. Furthermore, miR-281, which is the most abundant miRNA in the gut tissue, is induced and repressed by Met- and EcR-mediated signalling, respectively. Systematic depletion using synthetic antagomir and phenotype examinations indicate that miR-281 is obligatory for the normal progression of blood digestion, ovarian development and reproduction. Collectively, this study unveils expression dynamics of microRNAs in the female gut tissue during the gonadotrophic cycle and demonstrates that they are affected by JH and 20E signalling.