Functional implications of the peptidoglycan recognition proteins in the immunity of the yellow fever mosquito, A edes aegypti

Peptidoglycan recognition proteins ( PGRP s) play essential roles in the immune systems of insects and higher animals against certain pathogens, including bacteria. In insects, most studies on the functions of PGRP s have been performed in D rosophila , with only limited studies in mosquitoes, which are important disease vectors. In the present study, we analysed the PGRP sequences of the yellow fever mosquito, A edes aegypti , acquired from two genome databases, and identified a total of seven PGRP genes; namely, PGRP ‐ S 1, ‐ SC 2, ‐ LA , ‐ LB , ‐ LC , ‐ LD and ‐ LE . Bacterial injection using the Gram‐negative bacteria E scherichia coli and the G ram‐positive bacteria M icrococcus luteus showed that three PGRP s responded directly to both bacterial stimuli. Subsequently, the transcriptional expression of six of these PGRP s was knocked down using double‐stranded RNA ‐injection‐based RNA interference ( RNA i). RNA i of the PGRP s resulted in different impacts on the immune responses of A e. aegypti to the two bacteria, as evidenced by the changes in mosquito survival rates after bacterial challenges as well as the differential regulation of several antimicrobial peptides and a number of other genes involved in mosquito immune pathways. Our data suggest that PGRP‐LC is a significant factor in mediating immune responses to both E . coli and M . luteus , and the other PGRP s play only minor roles against these two bacteria, with PGRP ‐ SC 2 and ‐ LB also serving as potential negative regulators for certain immune pathway(s) in A e. aegypti .