A Blood Meal Enhances Innexin mRNA Expression in the Midgut, Malpighian Tubules, and Ovaries of the Yellow Fever Mosquito Aedes aegypti.

Travis Calkins,Peter Piermarini

doi:10.3390/insects8040122

Abstract

Mosquitoes are vectors of pathogens that cause diseases of medical and veterinary importance. Female mosquitoes transmit these pathogens while taking a blood meal, which most species require to produce eggs. The period after a blood meal is a time of extreme physiological change that requires rapid coordination of specific tissues. Gap junctions (GJ) are intercellular channels that aid in the coordination of cells within tissues via the direct transfer of certain small molecules and ions between cells. Evolutionarily distinct groups of proteins form the gap junctions of vertebrate and invertebrate animals (connexins and innexins, respectively). Aedes aegypti mosquitoes possess six genes encoding innexins: inx1, inx2, inx3, inx4, inx7, and inx8. The goal of this study was to identify potential roles of innexins in the physiology of mosquitoes after a blood meal by using qPCR to quantify their mRNA expression in adult females at 3 h and 24 h post-blood meal (PBM) relative to non-blood-fed controls. We found that at 24 h PBM, expression levels of inx2, inx3, and inx4 mRNAs increased; inx2 was the most highly upregulated innexin in key tissues associated with blood-meal digestion and egg production (i.e., the midgut and ovaries, respectively). However, knocking down inx2 mRNA levels by over 75% via RNA interference had no significant effect on fecundity. Altogether, our results suggest that a blood meal influences the molecular expression of innexins in mosquitoes, but their specific physiological roles remain to be elucidated.

Highlights

Mosquitoes transmit many pathogens that cause deadly and debilitating diseases
At 3 h post-blood meal (PBM), there were no significant differences in innexin mRNA levels between blood-fed and non-blood-fed mosquitoes (Supplementary Figure S1)
We found that inx2 and inx3 were upregulated by 24 h PBM in the whole insect, which can in part be attributed to an upregulation of inx2 in the Malpighian tubules, midgut, and ovaries, and inx3 in the ovaries (Figure 1)

Summary

Introduction

The yellow fever mosquito, Aedes aegypti, is the primary vector of chikungunya, dengue, yellow fever, and Zika viruses. These pathogens are transmitted when an infected female mosquito feeds on a vertebrate host; females require vertebrate blood in order to produce eggs. Intercellular channels known as gap junctions allow for endocrine signals to be rapidly shared among adjacent cells within a tissue by mediating the direct transport of ions, small molecules, and second messengers between cells [2]. Gap junctions are comprised of proteins known as connexins in vertebrates and innexins in invertebrates; they are evolutionarily distinct proteins that have convergently evolved to share similar structure and function [3,4]. The physiological roles of gap junctions in mosquitoes have only recently begun to emerge

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