Wolbachia inhibits ovarian formation and increases blood feeding rate in female Aedes aegypti

Abstract

Wolbachia, a gram-negative endosymbiotic bacterium widespread in arthropods, is well-known for changing the reproduction of its host in ways that increase its rate of spread, but there are also costs to hosts that can reduce this. Here we investigated a novel reproductive alteration of Wolbachia wAlbB on its host Aedes aegypti, using studies on mosquito life history traits, ovarian dissection, as well as gene expression assays. We found that an extended period of the larval stage as well as the egg stage (as previously shown) can increase the proportion of Wolbachia-infected females that become infertile; an effect which was not observed in uninfected females. Infertile females had incomplete ovarian formation and also showed a higher frequency of blood feeding following a prior blood meal, indicating that they do not enter a complete gonotrophic cycle. Treatments leading to infertility also decreased the expression of genes related to reproduction, especially the vitellogenin receptor gene whose product regulates the uptake of vitellogenin (Vg) into ovaries. Our results demonstrate effects associated with the development of infertility in wAlbB-infected Ae. aegypti females with implications for Wolbachia releases. The results also have implications for the evolution of Wolbachia infections in novel hosts.

Fitness costs ofWolbachiashift in locally‐adaptedAedes aegyptimosquitoes

“…This effect was Wolbachia ‐specific because uninfected females stored for the same amount of time never became infertile. The effects of egg storage on infertility are similar to those described previously for the w AlbB infection (Lau et al, 2021a, 2022) but substantially weaker, with ~50% infertility observed after only 9 weeks for w AlbB. The weakening of cytoplasmic incompatibility is likely due to partial or complete loss of Wolbachia during egg quiescence as demonstrated previously for w Mel (Lau et al, 2021a).…”

“…We showed previously that the w AlbB Wolbachia strain causes female mosquitoes to become infertile if they hatch from stored eggs (Lau et al, 2021a, 2022). We scored the proportion of females used in crosses in Figure 4 that laid eggs as a measure of infertility, although we note that the storage period to induce this effect is much longer than described previously for wA lbB (Lau et al, 2021a).…”

“…How to cite this article: Ross, P.A. & Hoffmann, A.A. (2022) Fitness costs of Wolbachia shift in locally-adapted Aedes aegypti mosquitoes. Environmental Microbiology, 24(12), 5749-5759.…”

A male-killing Wolbachia endosymbiont is concealed by another endosymbiont and a nuclear suppressor

“…Pathogenic effects of Wolbachia have been described previously, including the w MelPop infection of D . melanogaster that shortens lifespan [ 48 ] and the introduced w AlbB strain in Aedes aegypti that can cause female infertility [ 49 ]. Mechanisms involved in MK could be studied further by developing a way of sexing early instar larvae of D .…”

Developing Wolbachia-based disease interventions for an extreme environment

“…In a second experiment, we measured quiescent egg viability in the wAlbB S, wMelM S and Uninfected S populations with eight replicate batches of eggs according to the procedure above. We then scored the proportion of infertile females hatching from quiescent eggs by rearing females to adulthood and dissecting ovaries [88]. Infertile females were defined as those lacking visible ovaries.…”