Multigenerational expression of antimicrobial peptides in Aedes aegypti exposed to Metarhizium anisopliae: Is trans-generational immune priming involved?

We assessed, for the first time, a multigenerational expression of antimicrobial peptides (AMPs) in Aedes aegypti larvae exposed to the entomopathogenic fungus, Metarhizium anisopliae, and correlated it with a possible involvement in trans-generational immune priming (TGIP). Aedes aegypti larvae were first exposed to blastospores or conidia of M. anisopliae CG 489 for 24 and 48 h, and the relative expression of AMPs were measured using quantitative Real-Time PCR. A suspension of conidia was prepared, and two different survival tests were conducted with different larval generations (F0, F1, and F2). In the first bioassay, the survival curves of the three generations were conducted separately and compared with their respective control groups. In the other bioassay, the survival curves of the F0, F1, and F2 generations were compared simultaneously against a naïve group exposed to Tween 80. In both survival tests, the F0 generation was more susceptible to M. anisopliae than subsequent generations. For molecular analyses related to TGIP, F0, F1, and F2 larvae were exposed to conidia, and their expression of AMPs was compared with their control groups and a naïve group. There was no differential expression of cecropin, defensin A or cathepsin B between generations. Lysozyme C, however, showed an increase in expression across generations, suggesting a role in TGIP. These discoveries may help us develop biological insecticides against mosquito larvae based on entomopathogenic fungi.