Infection of Wolbachia may improve the olfactory response of Drosophila

The endosymbiotic bacterium Wolbachia infects various insects and is primarily known for its ability to manipulate host reproduction. Recent investigations reveal that Wolbachia also affects the activity of somatic cells. We here demonstrated by trap method and T-maze that Wolbachia infection had significant impact on the olfactory response of Drosophila simulans. Wolbachia-infected flies took shorter time to enter the food trap and were more sensitive to odorant in T-maze than those uninfected controls. The time of olfactory response was relative to Wolbachia density in flies. Wolbachia density in 15-day-old flies that were caught in a shorter time (less than 60 min) by food trap was significantly higher than those taken in a longer time (more than 100 min). Quantitative RT-PCR showed that the transcript of an important odorant receptor gene or83b in flies with fast olfactory response was significantly more than those with slow olfactory response. These results suggest that Wolbachia might increase olfactory response of flies by regulating the expression of olfaction-related genes in hosts.