Regulation of arginine methyltransferase 3 by a Wolbachia-induced microRNA in Aedes aegypti and its effect on Wolbachia and dengue virus replication.

The gram-negative endosymbiotic bacteria, Wolbachia, have been found to colonize a wide range of invertebrates, including over 40% of insect species. Best known for host reproductive manipulations, some strains of Wolbachia have been shown to reduce the host life span by about 50% and inhibit replication and transmission of dengue virus (DENV) in the mosquito vector, Aedes aegypti. The molecular mechanisms underlying these effects still are not well understood. Our previous studies showed that Wolbachia uses host microRNAs (miRNAs) to manipulate host gene expression for its efficient maintenance and limiting replication of DENV in Ae. aegypti. Protein arginine methyltransferases are structurally and functionally conserved proteins from yeast to human. In mammals, it has been reported that protein arginine methyltransferases such as PRMT1, 5 and 6 could regulate replication of different viruses. Ae. aegypti contains eight members of protein arginine methyltransferases (AaArgM1-8). Here, we show that the wMelPop strain of Wolbachia introduced into Ae. aegypti significantly induces the expression of AaArgM3. Interestingly, we found that Wolbachia uses aae-miR-2940, which is highly upregulated in Wolbachia-infected mosquitoes, to upregulate the expression of AaArgM3. Silencing of AaArgM3 in a mosquito cell line led to a significant reduction in Wolbachia replication, but had no effect on the replication of DENV. These results provide further evidence that Wolbachia uses the host miRNAs to manipulate host gene expression and facilitate colonization in Ae. aegypti mosquito.