Abstract
Entomopathogenic fungi represent a promising class of bio-insecticides for mosquito control. Thus, detailed knowledge of the molecular mechanisms governing anti-fungal immune response in mosquitoes is essential. In this study, we show that CLSP2 is a modulator of immune responses during anti-fungal infection in the mosquito Aedes aegypti. With a fungal infection, the expression of the CLSP2 gene is elevated. CLSP2 is cleaved upon challenge with Beauveria bassiana conidia, and the liberated CLSP2 CTL-type domain binds to fungal cell components and B. bassiana conidia. Furthermore, CLPS2 RNA interference silencing significantly increases the resistance to the fungal challenge. RNA-sequencing transcriptome analysis showed that the majority of immune genes were highly upregulated in the CLSP2-depleted mosquitoes infected with the fungus. The up-regulated immune gene cohorts belong to melanization and Toll pathways, but not to the IMD or JAK-STAT. A thioester-containing protein (TEP22), a member of α2-macroglobulin family, has been implicated in the CLSP2-modulated mosquito antifungal defense. Our study has contributed to a greater understanding of immune-modulating mechanisms in mosquitoes.
Highlights
Female mosquitoes require repeated blood feedings during their life cycle to satisfy their reproductive nutritional needs and, as a consequence, they serve as vectors of numerous human diseases [1]
CLSP2 composed of serine protease and lectin domains functions as a modulator of the mosquito immune system during the anti-fungal response
Transcriptome analysis indicated that the Toll pathway and melanization genes are highly up-regulated in CLSP2 RNA interference depleted mosquitoes infected with the fungus Beauveria bassiana
Summary
Female mosquitoes require repeated blood feedings during their life cycle to satisfy their reproductive nutritional needs and, as a consequence, they serve as vectors of numerous human diseases [1]. Malaria, transmitted by the Anopheles genus, is the most devastating vector-borne human disease and causes about one million deaths per year. The annual number of cases of Dengue fever, a viral disease transmitted by Aedes aegypti, has reached over a hundred million. Major reasons for this serious situation include the lack of effective vaccines against major mosquito-borne diseases, rapidly developing drug and insecticide resistance, and socio-economic problems in endemic countries. Fungal pathogens still require improvements due to the relatively low virulence when compared with chemical pesticides [3]. Detailed studies of antifungal immunity in mosquitoes are essential for future improvements of fungal biocontrol agents
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