Regulation of antimicrobial peptides by juvenile hormone and its receptor, Methoprene-tolerant, in the mosquito Aedes aegypti

Abstract

The trade-off between reproduction and immunity has been established for a number of insect species. However, the regulatory mechanisms governing this event is not well understood. In the mosquito Aedes aegypti, the vector of dangerous human arboviral diseases, juvenile hormone (JH) is required for the female post-eclosion development and reproductive maturation. In this study, we have revealed the JH negative effect on the expression of immunity-related genes, such as antimicrobial peptides (AMPs), during the post-eclosion phase of the female mosquito gonadotrophic reproductive cycle. Mosquitoes treated with JH became more sensitive to microbial infection. Mosquitoes subjected to the RNA interference knockdown (RNAi) of the JH receptor, Methoprene-tolerant (Met), showed increased expression of several AMP genes. Met binds to the E-box-like recognition motifs in the regulatory region of the diptericin (Dpt) gene, indicating that JH can suppress the Dpt gene expression through its receptor Met. Hence, JH is involved in the modulation of immune responses during the post-eclosion phase of reproduction. The RNAi knockdown of the peptidoglycan recognition protein (PGRP-LC) led to a significant reduction of the Dpt transcript level, indicating the PGRP-LC activating role on this AMP gene. Thus, Dpt appeared to be under the dual regulation of both the JH and the immune deficiency (IMD) signaling pathways. Our study provides a better understanding of how JH regulates insect immunity in adult mosquitoes.

Keywords: Aedes aegypti; Antimicrobial peptide; Diptericin; Innate immunity; Juvenile hormone; Methoprene-tolerant.