Biology subjects

Sigle, L. T.

Publications and source records attributed to Sigle, L. T..

3 recordsLinked to original sources

bioRxiv2022

Alpha-mannosidase-2 modulates arbovirus infection in a pathogen- and Wolbachia-specific manner in Aedes aegypti mosquitoes

Multiple Wolbachia strains can block pathogen infection, replication, and/or transmission in Aedes aegypti mosquitoes under both laboratory and field conditions. However, Wolbachia effects on pathogens can be highly variable across systems and the factors governing this variability are not well understood. It is increasingly clear that the mosquito host is not a passive player in which Wolbachia governs pathogen transmission phenotypes; rather, the genetics of the host can significantly modulate Wolbachia-mediated pathogen blocking. Specifically, previous work linked variation in Wolbachia pathogen blocking to polymorphisms in the mosquito alpha-mannosidase 2 (Man2) gene. Here we use CRISPR-Cas9 mutagenesis to functionally test this association. We developed Man2 knockouts and examined effects on both Wolbachia and virus levels, using both dengue virus (DENV; Flaviviridae) and Mayaro virus (MAYV; Togaviridae). Wolbachia titers were significantly elevated in Man2 knockout (KO) mosquitoes, but there were complex interactions with virus infection and replication. In Wolbachia-uninfected mosquitoes, the Man2 KO mutation was associated with decreased DENV titers, but in a Wolbachia-infected background, the Man2 KO mutation significantly modulated virus blocking. In contrast, the Man2 KO mutation significantly increased MAYV replication in Wolbachia-uninfected mosquitoes and did not affect Wolbachia-mediated virus blocking. These results demonstrate that Man2 modulates arbovirus infection in Ae. aegypti mosquitoes in a pathogen- and Wolbachia-specific manner, and that Wolbachia-mediated pathogen blocking is a complex phenotype dependent on the mosquito host genotype and the pathogen. These results have significant impact for the design and use of Wolbachia-based strategies to control vector-borne pathogens.

microbiology↗

bioRxiv2022

The IMD and JNK pathways drive the functional integration of the immune and circulatory systems of mosquitoes

The immune and circulatory systems of animals are functionally integrated. In mammals, the spleen and lymph nodes filter and destroy microbes circulating in the blood and lymph, respectively. In insects, immune cells that surround the heart valves (ostia), called periostial hemocytes, destroy pathogens in the areas of the body that experience the swiftest hemolymph (blood) flow. An infection recruits additional periostial hemocytes, amplifying heart-associated immune responses. Although the structural mechanics of periostial hemocyte aggregation have been defined, the genetic factors that regulate this process remain less understood. Here, we conducted RNAseq in the African malaria mosquito, Anopheles gambiae, and discovered that an infection upregulates multiple components of the IMD and JNK pathways in the heart with periostial hemocytes. This upregulation is greater in the heart with periostial hemocytes than in the circulating hemocytes or the entire abdomen. RNAi-based knockdown then showed that the IMD and JNK pathways drive periostial hemocyte aggregation and alter phagocytosis and melanization on the heart, thereby demonstrating that these pathways regulate the functional integration between the immune and circulatory systems. Understanding how insects fight infection lays the foundation for novel strategies that could protect beneficial insects and harm detrimental ones.

immunology↗

bioRxiv2019

Artificial selection finds new hypotheses for the mechanism of Wolbachia-mediated dengue blocking in mosquitoes

Wolbachia is an intracellular bacterium that blocks virus replication in insects and has been introduced into the mosquito, Aedes aegypti for the biocontrol of arboviruses including dengue, Zika and chikungunya. Despite ongoing research, the mechanism of Wolbachia-mediated virus blocking remains unclear. We recently used experimental evolution to reveal that Wolbachia-mediated dengue blocking could be selected upon in the A. aegypti host and showed evidence that strong levels of blocking could be maintained by natural selection. In this study, we investigate the genetic variation associated with blocking and use these analyses to generate testable hypotheses surrounding the mechanism of Wolbachia-mediated dengue blocking. From our results, we hypothesise that Wolbachia may block virus replication by increasing the regeneration rate of mosquito cells via the Notch signalling pathway. We also propose that Wolbachia modulates the hosts transcriptional pausing pathway either to prime the hosts anti-viral response or to directly inhibit viral replication.

evolutionary biology↗