Assessing desiccation tolerance's impact on Aedes aegypti midgut infection - Understanding how adaptation of mosquitoes to persist at low humidity affects their potential to be successful vectors of human pathogens can lead to novel ways to help prevent or slow the spread of vector-borne diseases. Environmental variation can create novel habitats, such as those with low humidity, for mosquitoes to thrive in. The ability to persist in habitats with low humidity results in mosquitoes with increased desiccation tolerance and can result in new molecular pathways governing interactions with human pathogens. Our understanding of the environmental and genetic factors that contribute to virus emergence and transmission is limited. In populations outside the U.S., success of Aedes aegypti in areas of reduced rainfall have been accompanied by an increased susceptibility for Zika virus. However, the genetic mechanisms driving these traits and their relationship to relative humidity remain poorly understood. We have identified two genes with dual roles in regulating midgut infection and in desiccation tolerance, suggesting that genes regulating midgut infection have a pleiotropic effect on desiccation tolerance or vice versa. We identified a peritrophic matrix (PM: a sac that envelops the bloodmeal in the midgut and can block arbovirus infection) gene that is upregulated in response to desiccation stress, and whose expression controls midgut susceptibility to Zika and chikungunya viruses. Additionally, we have identified a detoxification gene that is upregulated in midgut cells in response to dengue virus infection, and is also highly expressed in oenocytes, the site of cuticular hydrocarbons (CHC) biosynthesis in the fat body (main metabolic organ). This proposal will address the central hypothesis that desiccation tolerance is accompanied by pleiotropic effects on vector competence through changes in midgut physiology and metabolism. In Aim 1 we will identify desiccation tolerance-induced changes in midgut physiology and structure that facilitate arbovirus infection by 1) demonstrating that PM formation alters midgut susceptibility by changing viral access to the midgut epithelium, 2) measuring PM-associated phenotypes and midgut cellular and molecular responses in lines maintained under low humidity, and 3) measuring PM-associated phenotypes and midgut cellular and molecular responses in mosquito Iines from the U.S naturally adapted to low humidity to validate our findings in natural populations. In Aim 2 we will investigate shared metabolic processes underlying desiccation tolerance and midgut infection by 1) identifying metabolites and metabolic processes underlying midgut infection and validate metabolites’ roles in midgut infection, 2) comparing metabolic profiles between mosquito lines maintained at low humidity, and 3) comparing metabolic profiles between U.S. field-collected lines naturally adapted to low humidity to determine if desiccation tolerance is correlated with metabolic profiles underlying dengue virus susceptibility. Our findings will crucially inform new genetically based control approaches such as gene drive technology.
