AwMelWolbachiavariant inAedes aegyptifrom field‐collectedDrosophila melanogasterwith increased phenotypic stability under heat stress

Abstract

Mosquito-borne diseases remain a major cause of morbidity and mortality. Population replacement strategies involving the wMel strain of Wolbachia are being used widely to control mosquito-borne diseases. However, these strategies may be influenced by temperature because wMel is vulnerable to heat. wMel infections in Drosophila melanogaster are genetically diverse, but few transinfections of wMel variants have been generated in Aedes aegypti. Here, we successfully transferred a wMel variant (termed wMelM) originating from a field-collected D. melanogaster into Ae. aegypti. The new wMelM variant (clade I) is genetically distinct from the original wMel transinfection (clade III), and there are no genomic differences between wMelM in its original and transinfected host. We compared wMelM with wMel in its effects on host fitness, temperature tolerance, Wolbachia density, vector competence, cytoplasmic incompatibility and maternal transmission under heat stress in a controlled background. wMelM showed a higher heat tolerance than wMel, likely due to higher overall densities within the mosquito. Both wMel variants had minimal host fitness costs, complete cytoplasmic incompatibility and maternal transmission, and dengue virus blocking under laboratory conditions. Our results highlight phenotypic differences betweenWolbachia variants and wMelM shows potential as an alternative strain in areas with strong seasonal temperature fluctuations.

Wolbachia wAlbB remains stable in Aedes aegypti over 15 years but exhibits genetic background-dependent variation in virus blocking

“…Our results show that, in an outbred genetic background, WB1 and WB2 had similar densities in both female whole bodies and male testes except for in the ovaries, where WB2 had higher density than did WB1. A similar observation was made in a recent study that compared the density of w Mel between a recently transinfected line and another line generated 10 year ago ( 50 ). It is predicated that CI genes would degrade over time in selectively neutral populations, starting with the sperm modification factor cifB , followed by the rescue factor cifA ( 51 ).…”

“…aegypti ( 59 , 60 ). The high sensitivity of w Mel to heat stress and other factors makes the transinfected mosquito difficult to establish in some areas in Vietnam and Brazil, where w AlbB and a heat-resistant w MelM variant have been proposed as an alternative because of their stability in extreme temperatures ( 41 , 50 , 61 , 62 ). When Wolbachia is to be deployed globally for arbovirus disease control, different Wolbachia strains may be required for regions with specific environmental or ecological conditions.…”

Attempts to use breeding approaches in Aedes aegypti to create lines with distinct and stable relative Wolbachia densities

“…These findings do not bode well for creating high and low-relative density lines for PB trait dissection or for field release. Continuing to explore naturally occurring distinct Wolbachia strains that vary in density genotype may be the only useful approach for field release (Gu et al 2022 ). These findings do suggest that there are moderating forces acting on symbiont loads that may help to maintain stable densities in the field once strains are released (Ahmad et al 2021 ; Frentiu et al 2014 ).…”

Humidity - The Overlooked Variable in Thermal Biology of Mosquito-Borne Disease

“…Finally, disease intervention efforts can also be directly or indirectly affected by variation in ambient temperature. Various insecticides (Glunt et al 2014;Akinwande et al 2021), entomopathogenic fungi (Kikankie et al 2010;Darbro et al 2011), andWolbachia transinfections (Murdock et al 2014a;Ulrichet al 2016;Ross et al 2017Ross et al , 2019Ross et al , 2020Foo et al 2019;Gu et al 2022) are thermally sensitive, indicating that the efficacy and cost of these interventions could vary seasonally, across geographic regions, and with future climate and land use change (Parham & Hughes 2015).…”

“…aegypti (Moreira et al 2009;Ye et al 2015;Aliota et al2016a, b). Experimental work has determined that w Mel infections are temperature sensitive, with high temperatures causing reductions inWolbachia density (Ulrich et al 2016;Ross et al2017Ross et al , 2019Ross et al , 2020Foo et al 2019;Gu et al 2022) and temperature variation affects the host-pathogen interaction and the outcome of infection in Wolbachia -infected mosquitoes (Murdocket al 2014a). Based on the relationship between temperature and water balance laid out in this paper, further experiments should examine whether Wolbachia infections are limited by temperature alone or by cellular water availability, and examine what role mosquito desiccation stress plays in limiting Wolbachia abundance within mosquitoes at varying temperature.…”