Differences in gene expression in field populations ofWolbachia-infectedAedes aegyptimosquitoes with varying release histories in northern Australia

Abstract

Aedes aegypti is the principal mosquito vector of dengue, yellow fever, Zika and chikungunya viruses. The wMel endosymbiotic bacteria Wolbachia pipientis has been introduced into this vector as a novel biocontrol strategy to stop transmission of these viruses. Mosquitoes with Wolbachia have been released in the field in North Queensland, Australia since 2011, at various locations and over several years, with populations remaining stably infected. Wolbachia infection is known to alter gene expression in its mosquito host, but whether (and how) this changes over the long-term in the context of field releases remains unknown. We sampled mosquitoes from Wolbachia-infected populations with different release histories along a time gradient and performed RNAseq to investigate gene expression changes in the insect host. We observed a significant impact on gene expression in Wolbachia- infected mosquitoes versus uninfected controls, but fewer genes had altered expression in the older releases (e.g. the year 2011) versus the more recent releases (e.g. 2017). Nonetheless, a fundamental signature of Wolbachia infection on host gene expression was observed across all releases, comprising upregulation of immunity and metabolism genes. There was limited downregulation of gene expression in the older releases, but significantly more in the most recent release. Our findings indicate that at > 8 years post-introgression into field populations, Wolbachia continues to profoundly impact host gene expression, particularly genes involved in insect immune response. We suggest that if gene expression changes underlie blocking of virus replication in Wolbachia-infected Ae. aegypti, then refractoriness of these mosquitoes to arboviruses may remain stable over the long-term.

Integrated de novo transcriptome of Culex pipiens mosquito larvae as a resource for genetic control strategies

“…Two thousand L 1 larvae of each strain were put in plastic trays filled with 2 L of spring water, and the trays were set up in triplicate. In each tray, the larvae were maintained as described above, and at L 4 , a pool of 10 larvae was collected and immediately stored in RNA later buffer (Thermo fisher Scientific, Ravenna, Italy) at −80 °C until RNA extraction [36][37][38] .…”