The Aquaporin Gene Family of the Yellow Fever Mosquito, Aedes aegypti

Abstract

BackgroundThe mosquito, Aedes aegypti, is the principal vector of the Dengue and yellow fever viruses. During feeding, an adult female can take up more than its own body weight in vertebrate blood. After a blood meal females excrete large amounts of urine through their excretion system, the Malpighian tubules (MT). Diuresis starts within seconds after the mosquito starts feeding. Aquaporins (AQPs) are a family of membrane transporters that regulate the flow of water, glycerol and other small molecules across cellular membranes in both prokaryotic and eukaryotic cells. Our aim was to identify aquaporins that function as water channels, mediating transcellular water transport in MTs of adult female Ae. aegypti.Methodology/Principal FindingsUsing a bioinformatics approach we screened genome databases and identified six putative AQPs in the genome of Ae. aegypti. Phylogenetic analysis showed that five of the six Ae. aegypti AQPs have high similarity to classical water-transporting AQPs of vertebrates. Using microarray, reverse transcription and real time PCR analysis we found that all six AQPs are expressed in distinct patterns in mosquito tissues/body parts. AaAQP1, 4, and 5 are strongly expressed in the adult female MT. RNAi-mediated knockdown of the MT-expressed mosquito AQPs resulted in significantly reduced diuresis.Conclusions/SignificanceOur results support the notion that AQP1, 4, and 5 function as water transporters in the MTs of adult female Ae. aegypti mosquitoes. Our results demonstrate the importance of these AQPs for mosquito diuresis after blood ingestion and highlight their potential as targets for the development of novel vector control strategies.

A comprehensive transcriptomic view of renal function in the malaria vector, Anopheles gambiae

“…6H and 5A). This is consistent with Aedes aegypti, where three of the six aquaporins identified are up-regulated 3 h after a blood-meal (Drake et al, 2010). Of the genes most highly enriched in the tubules upon blood-feeding , only one is 'named' -Prestin -and the vast majority appear to be involved in enzymatic and metabolic processes (Table 4).…”

“…Four of the seven predicted Anopheles aquaporins (Drake et al, 2010) are expressed in the tubules, and each is massively up-regulated in adult when compared to larva (Fig. 4A, Supplementary Table 1).…”

Transport of H+, Na+ and K+ across the posterior midgut of blood-fed mosquitoes (Aedes aegypti)

“…The sodium pump has been suggested to play a role in creation of osmotic gradients driving transcellular water transport through aquaporins 1, 2, 4 and 5 which are expressed in the midgut. Aquaporins 1, 2 and 4 are down regulated by 3 h after the blood meal, corresponding to the time by which excretion of the bulk of the blood meal-derived water has been excreted (Drake et al, 2010). Furthermore, the mosquito releases diuretic peptides from the brain such as aedeskinin and mosquito naturietic peptide into the hemolymph immediately after feeding; these then stimulate the fluid-secreting Malpighian tubules of the mosquito (Beyenbach, 2012).…”

“…The peak phase of diuresis occurs around six minutes after the acquisition of a blood meal and steadily declines until two hours after feeding (Williams et al, 1983). It is interesting to note that the mosquito does not completely excrete the entire plasma/water portion of the meal, but begins to reduce the number of water-transporting aquaporins in the posterior midgut after diuresis (Sanders et al, 2003;Drake et al, 2010). It is believed that the mosquito retains this fluid that surrounds the erythrocytes in the posterior midgut in order to serve as a template for the formation of the peritrophic matrix (Sanders et al, 2003).…”

Blood serum and BSA, but neither red blood cells nor hemoglobin can support vitellogenesis and egg production in the dengue vector Aedes aegypti

“…aegypti mosquitoes excrete up to 80% of the meals volume within the first hours (Drake, Boudko et al 2010;Drake, Price et al 2012). The meal becomes more concentrated and therefore easier to digest and the mosquito loses weight which restores its flight capabilities.…”