Autophagic regulation of Wolbachia in Drosophila
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Over the past 20 years numerous major arbovirus outbreaks including Yellow Fever virus, West Nile virus, dengue virus, Chikungunya virus, and most recently Zika virus, have highlighted the need for novel methods of control for these diseases. Wolbachia are maternally transmitted endosymbionts that inhabit a large portion of arthropods, including Aedes aegypti, Aedes albopictus, and Culex pipiens, which are three mosquito vectors that transmit these viruses. Wolbachia have been shown to reduce vector competency in these mosquitos. However, the molecular pathways at the Wolbachia-host cell interface are mostly unknown. For fundamental biological questions and for vector control approaches, there is a need to further our understanding of host-symbiont interactions at the molecular level. From this, autophagy has been suggested as one possible mechanism at this interface. Autophagy is a conserved, cellular, homeostasis process that involves degrading cytoplasmic contents, including organelles and protein aggregates. Canonical autophagy can be a large, bulky process, or a more targeted, selective one. There is the potential for Wolbachia to both benefit from the nutrients generated from bulk autophagy, but also be targeted in the host’s immune response, as selective autophagy has been shown to aid in removal of intracellular pathogens. Here we describe how autophagy plays a role in regulating Wolbachia in Drosophila melanogaster as a model for mosquitos. Using antibody and FISH staining we visualized differences in Wolbachia density after knocking down autophagy genes. Knocking down Atg1, an important factor in initiating autophagy, was sufficient for increasing Wolbachia density in polar cells, but other components like Atg7 and Ref(2)p were not. Results varied based on the Wolbachia strain infection, showing that autophagy differentially affects Wolbachia according to the strain. These findings further our understanding of molecular host-symbiont interactions and provide additional tools to Wolbachia based vector control strategies.