Dehydration Alters Transcript Levels in the Mosquito Midgut, Likely Facilitating Rapid Rehydration following a Bloodmeal

Abstract

The mosquito midgut is an important site for bloodmeal regulation while also acting as a primary site for pathogen exposure within the mosquito. Recent studies show that exposure to dehydrating conditions alters mosquito bloodfeeding behaviors as well as post-feeding regulation, likely altering how pathogens interact with the mosquito. Unfortunately, few studies have explored the underlying dynamics between dehydration and bloodmeal utilization, and the overall impact on disease transmission dynamics remains veiled. In this study, we find that dehydration-based feeding in the yellow fever mosquito, Aedes aegypti, prompts alterations to midgut gene expression, as well as subsequent physiological factors involving water control and post-bloodfeeding (pbf) regulation. Altered expression of ion transporter genes and aquaporin 2 (AQP2) in the midgut of dehydrated mosquitoes as well as the rapid reequilibration of hemolymph osmolality after a bloodmeal indicate an ability to expedite fluid and ion processing. These alterations ultimately indicate that female A. aegypti employ mechanisms to ameliorate the detriments of dehydration by imbibing a bloodmeal, providing an effective avenue for rehydration. Continued research into bloodmeal utilization and the resulting effects on arthropod-borne transmission dynamics becomes increasingly important as drought prevalence is increased by climate change.

Keywords: Aedes aegypti; aquaporin; bloodfeeding; ecdysteroid kinase; ion transport; osmolality; transcriptomics.

Figure 1

Functional enrichment analyses for non-bloodfed A. aegypti midguts. (A), circular gene ontology (CirGO) representations of reduced and visualized gene ontology (REVIGO) terms in the non-bloodfed/dehydrated group over the non-bloodfed/non-dehydrated group (N7_N1); (B), CirGO-REVIGO representations for the non-bloodfed/non-dehydrated group over the non-bloodfed/dehydrated group (N1_N7). REVIGO groupings are included in Supplementary Table S3 and significant g:Profiler terms are included in Supplementary Table S4 with “intersections” indicating the genes responsible for GO categorization. CLC labels represent significant transcripts identified with the QIAGEN CLC pipeline; DK, the DESeq2-Kallisto pipeline; and DS, the DESeq2-Sailfish pipeline.

Figure 2

Log2 fold-change comparisons and median-of-ratios normalized mean expression averages across all samples for all differentially expressed genes identified by DESeq2 pipelines. (A), comparison between the non-bloodfed/dehydrated group over the non-bloodfed/non-dehydrated group (N7_N1); (B), comparison between the bloodfed/dehydrated group over the bloodfed/non-dehydrated group (Y7_Y1). Yellow circles denote genes that were identified through the DESeq-Sailfish pipeline; red circles, DESeq-Kallisto pipeline; and black circles were genes identified by both pipelines, with the highest mean expression pipeline used. Significantly expressed transcripts are included in Supplementary Table S1 and sample-specific normalized mean expression values are included in Supplementary Table S5.

Figure 3

Hemolymph osmolality and bloodfed midgut volume for A. aegypti subjected to various treatments. (A), hemolymph osmolality for non-dehydrated (N1), dehydrated (N7), and post-dehydration bloodfed (Y7) A. aegypti (N = 30); (B), midgut size comparisons for bloodfed A. aegypti after 18 h of exposure to non-dehydrating (Y1), dehydrating (Y7), or colony conditions (N = 86). Significance was determined via ANOVA and Tukey’s HSD test.