Serine hydroxymethyltransferase controls blood-meal digestion in the midgut of Aedes aegypti mosquitoes

Abstract

AbstractBackgroundFemaleAedes aegyptimosquitoes are vectors of arboviruses that cause diverse diseases of public health significance. Blood protein digestion by midgut proteases provides anautogenous mosquitoes with the nutrients essential for oocyte maturation and egg production. Midgut-specific miR-1174 affects the functions of the midgut through its target geneserine hydroxymethyltransferase(SHMT). However, less is known aboutSHMT-regulated processes in blood digestion by mosquitoes.MethodsRNAi ofSHMTwas realized by injection of the double-stranded RNA at 16 h post-eclosion. The expression ofSHMTat mRNA level and protein level was assayed by real-time PCR and Western blotting, respectively. Statistical analyses were performed with GraphPad7 using Student’s t-test.ResultsHere, we confirmed that digestion of blood was inhibited inSHMTRNAi-silenced femaleA. aegyptimosquitoes. Evidence is also presented that allSHMT-depleted female mosquitoes lost their flight ability and died within 48 h of a blood meal. Furthermore, most examined digestive enzymes responded differently in their transcriptional expression to RNAi depletion ofSHMT, with some downregulated, some upregulated and some remaining stable. Phylogenetic analysis showed that transcriptional expression responses toSHMTsilence were largely unrelated to the sequence similarity between these enzymes.ConclusionsOverall, this research shows thatSHMTwas expressed at a low level in the midgut ofAedes aegyptimosquitoes, but blood-meal digestion was inhibited whenSHMTwas silenced. Transcriptional expressions of different digestive enzymes were affected in response toSHMTdepletion, suggesting thatSHMTis required for the blood-meal digestion in the midgut and targetingSHMTcould provide an effective strategy for vector mosquito population control.