An Aedes aegypti seryl-tRNA synthetase paralog controls bacteroidetes growth in the midgut

Insect gut microbiota plays important roles in host physiology, such as nutrition, digestion, development, fertility, and immunity. We have found that in the intestine of Aedes aegypti , SLIMP (seryl-tRNA synthetase like insect mitochondrial protein) knockdown followed by a blood meal promotes dysbiosis, characterized by the overgrowth of a specific bacterial phylum, Bacteroidetes. In turn, the latter decreased both infection rates and Zika virus prevalence in the mosquitoes. Previous work in Drosophila melanogaster showed that SLIMP is involved in protein synthesis and mitochondrial respiration in a network directly coupled to mtDNA levels. There are no other reports on this enzyme and its function in other insect species. Our work expands the knowledge of the role of these SerRS paralogs. We show that A. aegypti SLIMP (AaeSLIMP) clusters with SLIMPs of the Nematocera sub-order, which have lost both the tRNA binding domain and active site residues, rendering them unable to activate amino acids and aminoacylate tRNAs. Knockdown of AaeSLIMP did not significantly influence the mosquitoes’ survival, oviposition, or eclosion. It also neither affected midgut cell respiration nor mitochondrial ROS production. However, it caused dysbiosis, which led to the activation of Dual oxidase and resulted in increased midgut ROS levels. Our data indicate that the intestinal microbiota can be controlled in a blood-feeding vector by a novel, unprecedent mechanism, impacting also mosquito vectorial competence towards zika virus and possibly other pathogens as well. Author Summary Aminoacyl-tRNA synthetases (aaRS) are a family of ubiquitous enzymes responsible for the attachment of specific amino acids to their cognate tRNAs. During evolution some aaRS acquired new domains and/or suffered gene duplications, resulting in the improvement and expansion of their functions some of them being specific to a group of organisms. A paralog of seryl-tRNA synthetase restricted to the class Insecta (SLIMP) is found in Arthropoda. Our goal was to explore the role of SLIMP in the female mosquito Aedes aegypti using RNA interference. We showed that A. aegypti SLIMP (AaeSLIMP) gene expression is up-regulated upon blood feeding through a heme-dependent signaling. Although AaeSLIMP knockdown neither impacted the mosquito survival nor oviposition, it provoked ROS levels augmentation in the midgut via Dual Oxidase activity in order to control the increase in the intestinal native microbiota, specifically bacteria of the Bacteroidetes phylum. Although dysbiosis can result from mitochondrial impairment, this is the first time that the absence of a mitochondrial enzyme is linked to intestinal microbiota without any visible effects in mitochondrial respiration and mitochondrial ROS production. Furthermore, Zika Virus infection of AaeSLIMP silenced mosquitoes is decreased when comparing to control, meaning that Bacteroidetes overgrowth may be protecting the female mosquito. Our data indicate that the intestinal microbiota can be controlled in a blood-feeding vector by a novel, unprecedent mechanism, impacting also mosquito vectorial competence towards zika virus and possibly other pathogens as well. ### Competing Interest Statement The authors have declared no competing interest.