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.
Highlights
Anautogenous mosquito females need vertebrate blood for reproduction
We show that four AQPs are expressed in the Malpighian tubules of adult females and that knockdown of three of them affects diuresis
In addition we identified seven putative AQPs encoded in the genome of the malaria mosquito Anopheles gambiae [19], eight in the Drosophila genome [20], six in the genomic sequence of the head louse Pediculus humanus [21], and seven in the genome of the red flour beetle Triboleum castaneum [22,23]
Summary
Anautogenous mosquito females need vertebrate blood for reproduction. The nutrients taken up with the blood are used to synthesize large amounts of yolk proteins that are deposited in the eggs during a process called vitellogenesis. During and after a blood meal female Ae. aegypti secrete large amounts of urine through their Malpighian tubules (MT). Diuretic hormones, released seconds after start of the blood meal, stimulate the MT cells to produce the second messenger molecule cAMP which activates transcellular diuresis by increasing transepithelial cation (Na+, K+) transport [2]. Another class of neuropeptide hormones, the kinins, increase intracellular calcium levels that regulate anion movement (Cl2) into the MT lumen [3,4]. Our aim was to identify aquaporins that function as water channels, mediating transcellular water transport in MTs of adult female Ae. aegypti
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