Evolutionary conserved miRNA regulation of fatty acyl-CoA reductase may underpin a role in the tsetse-Wigglesworthia symbiosis

Tsetse flies (family Glossinidae), native to Sub-Saharan Africa, are biting flies primarily of interest as the vectors of African trypanosomes, the causative agent of the neglected tropical disease African trypanosomiasis. Fully hematophagous, the blood-feeding diet of tsetse flies is deficient in B vitamins including folate, biotin, and thiamine which contribute to reproduction. As a result, the tsetse fly is reliant on mutualistic Wigglesworthia bacteria in the bacteriome organ to provide B vitamins and both species exist in an ancient, evolutionarily interwoven symbiosis. As the function of Wigglesworthia in this symbiosis has been elucidated, there is a research gap in understanding how nutrient provisioning accommodates changing nutritional needs across the life cycle of the fly. Previous work has identified microRNAs (miRNAs or miRs), which regulate post-transcriptional expression, as potential regulators in the nutritional symbiosis of multiple insect species including tsetse flies. Of particular interest in tsetse is the miR-31 regulation of a fatty Acyl-CoA reductase gene, orthologous to Drosophila CG5065, with both the gene and miRNA found to be overly expressed in mated bacteriome tissue relative to adjacent aposymbiotic tissue. This suggests a role in the symbiosis with phylogenetic research in tsetse and observations of genome-wide RNAi in Drosophila further suggesting that this role is in epithelial integrity. In this study, we examine the phenotypes resulting in disruption of the Fatty Acyl-CoA reductase through RNAi and antagomirs through microscopy, through gene expression using RT-PCR, and fecundity and survival assays. Ultimately, understanding this obligate symbiosis may contribute to vector control.