BackgroundMosquitoes feed on plant-derived fluids such as nectar and sap and are exposed to bioactive molecules found in this dietary source. However, the role of such molecules on mosquito vectorial capacity is unknown. Weather has been recognized as a major determinant of the spread of dengue, and plants under abiotic stress increase their production of polyphenols.ResultsHere, we show that including polyphenols in mosquito meals promoted the activation of AMP-dependent protein kinase (AMPK). AMPK positively regulated midgut autophagy leading to a decrease in bacterial proliferation and an increase in vector lifespan. Suppression of AMPK activity resulted in a 6-fold increase in midgut microbiota. Similarly, inhibition of polyphenol-induced autophagy induced an 8-fold increase in bacterial proliferation. Mosquitoes maintained on the polyphenol diet were readily infected by dengue virus.ConclusionThe present findings uncover a new direct route by which exacerbation of autophagy through activation of the AMPK pathway leads to a more efficient control of mosquito midgut microbiota and increases the average mosquito lifespan. Our results suggest for the first time that the polyphenol content and availability of the surrounding vegetation may increase the population of mosquitoes prone to infection with arboviruses.

BackgroundProtein Tyrosine Phosphatases (PTPs) are enzymes that catalyze phosphotyrosine dephosphorylation and modulate cell differentiation, growth and metabolism. In mammals, PTPs play a key role in the modulation of canonical pathways involved in metabolism and immunity. PTP1B is the prototype member of classical PTPs and a major target for treating human diseases, such as cancer, obesity and diabetes. These signaling enzymes are, hence, targets of a wide array of inhibitors. Anautogenous mosquitoes rely on blood meals to lay eggs and are vectors of the most prevalent human diseases. Identifying the mosquito ortholog of PTP1B and determining its involvement in egg production is, therefore, important in the search for a novel and crucial target for vector control.Methodology/Principal FindingsWe conducted an analysis to identify the ortholog of mammalian PTP1B in the Aedes aegypti genome. We identified eight genes coding for classical PTPs. In silico structural and functional analyses of proteins coded by such genes revealed that four of these code for catalytically active enzymes. Among the four genes coding for active PTPs, AAEL001919 exhibits the greatest degree of homology with the mammalian PTP1B. Next, we evaluated the role of this enzyme in egg formation. Blood feeding largely affects AAEL001919 expression, especially in the fat body and ovaries. These tissues are critically involved in the synthesis and storage of vitellogenin, the major yolk protein. Including the classical PTP inhibitor sodium orthovanadate or the PTP substrate DiFMUP in the blood meal decreased vitellogenin synthesis and egg production. Similarly, silencing AAEL001919 using RNA interference (RNAi) assays resulted in 30% suppression of egg production.Conclusions/SignificanceThe data reported herein implicate, for the first time, a gene that codes for a classical PTP in mosquito egg formation. These findings raise the possibility that this class of enzymes may be used as novel targets to block egg formation in mosquitoes.

Lipid peroxidation is promoted by the quasi-lipoxygenase (QL) activity of heme proteins and enhanced by the presence of free calcium. Unlike mammalian plasma, the hemolymph of Rhodnius prolixus, a vector of Chagas disease, contains both a free heme-binding protein (RHBP) and circulating lipoproteins. RHBP binds and prevents the heme groups of the proteins from participating in lipid peroxidation reactions. Herein, we show that despite being bound to RHBP, heme groups promote lipid peroxidation through a calcium-dependent QL reaction. This reaction is readily inhibited by the presence of ethylene glycol tetraacetic acid (EGTA), the antioxidant butylated hydroxytoluene or micromolar levels of the main yolk phosphoprotein vitellin (Vt). The inhibition of lipid peroxidation is eliminated by the in vitro dephosphorylation of Vt, indicating that this reaction depends on the interaction of free calcium ions with negatively charged phosphoamino acids. Our results demonstrate that calcium chelation mediated by phosphoproteins occurs via an antioxidant mechanism that protects living organisms from lipid peroxidation.

Mosquitoes are major vectors of human diseases. This is mainly due to their requirement for a blood meal to lay eggs which allows the transmission of pathogens to the human being. Our aim is to identify proper molecular targets in order to block blood feeding and impair egg formation. In their early days of adult life mosquitoes feed on vegetal fluids and their midgut is continuously loaded with several bioactive compounds including polyphenols. We observed that polyphenol‐fed mosquitos dramatically increase their average lifespan (Control T 1/2 ± 15‐18 days, Polyphenol‐fed T1/2± 20‐32 days). Polyphenols also reduced the body triglyceride content from 20‐75 %. They trigger midgut autophagy which leads to a 40 % decrease on bacterial loads. Such mechanisms are mimicked by the activation of the mosquito AMPK and abolished by RNAi‐mediated silencing of this gene. Thus the presence of polyphenol on early mosquito meals optimizes mosquito metabolism and immunity and its chances of finding its first blood meal. After a blood meal digestion will take place in mosquito midgut. Blood‐derived nutrients allow yolk synthesis and egg formation. Blood feeding affects the expression of the mosquito PTP‐1B (AaPTP1B) in tissues critically involved in the synthesis and storage of vitellogenin (Vg), the major yolk protein. The protein tyrosine phosphatase inhibitor sodium orthovanadate or the PTP substrate DiFMUP decreased Vg synthesis and egg production. Also, silencing of AaPTP1B using by RNAi assays suppressed by 30 % egg production. In conclusion, the above results show that mosquito signaling pathways regulated by AMPK and PTP1B are proper targets to block blood feeding and egg formation. Future research strategies should be designed to generate novel cell signaling‐based insecticides that simultaneously decrease mosquito lifespan and reproduction. Grant Funding Source: Supported by CNPq, INCT‐EM, FAPERJ