The mosquito’s tegument is a complex structure with layers (epicuticle, exo-cuticle, endo-cuticle, and epidermis) covered by a waxy coating. Insects rely on their physical barriers (e.g., tegument and epithelial cells of the gut), as well as cellular and humoral components of their innate immune system to protect themselves from invading fungi and other microorganisms. They have a thin cell wall without ß-glucans to act as camouflage against the immune system of the insect hosts. On the other hand, blastospores are polymorphic yeast-like cells produced within the insect hemocoel. Conidia are terrestrial spores with hydrophobic walls and are generally more resistant to desiccation than blastospores. However, both are distinct in several ways. Ĭonidia and blastospores (similar to hyphal bodies) of EPF have been tested to control Ae. After exhausting the hosts’ nutrients, conidiogenesis, the production of new conidia, occurs on the cadaver. The following steps include blastospore proliferation, toxin production, and hyphal development that take up the energy resource from the insect. To overcome the tegument, the fungus uses a combination of mechanical pressure and an array of cuticle-degrading enzymes. The EPF infection process starts with the attachment by conidia and germ tube development.
(Hypocreales: Cordycipitaceae) is an entomopathogenic fungus (EPF) with the potential to control mosquitoes of public health concern. Therefore, biological controls might represent a complementary tool for controlling Aedes sp.īeauveria bassiana (Bals.) Vuill. aegypti due to the overuse of chemical insecticides. However, there are many reports of insecticide resistance developed by Ae. Classical mosquito control methods are based on chemical insecticides and integrated pest management practices to eliminate larval habitats. In particular, Aedes aegypti (Diptera: Culicidae) transmits dengue (DENV), chikungunya (CHIKV), yellow fever (YF) and Zika (ZIKV) viruses that causes morbidity and mortality in subtropical and tropical countries, including Brazil. bassiana CG 206 demonstrating how this fungus can infect, affect, and kill Ae. Our data reports a complex interplay between Ae. bassiana CG 206 occluded the midgut, reduced THC, did not stimulate PO activity, and downregulated AMP expression in larvae, all of which allowed the fungus to impair the larvae to facilitate infection. At 48 h, blastospores and conidia increased the expression of defensin A suggesting this may be an essential AMP against EPF. At 24 h, cathepsin B was upregulated by infection with conidia, whereas both propagules resulted in a downregulation of cecropin and defensin A. Irrespective of the propagule, the PO activity increased only at 48 h. For the larvae exposed to conidia, these interactions were observed only at 48 h. Regardless of the time, SEM revealed hemocytes adhering to, and nodulating, blastospores. By 48 h, the oenocytoid percentage increased significantly ( P < 0.05) in larvae exposed to blastospores however, the other hemocyte types did not change significantly. By 24 h after exposure to conidia the percentage of granulocytes and oenocytoids increased while the prohemocytes decreased. Both propagules decreased the THC regardless of the time. Propagules invaded mosquitoes through the midgut, and blastopores were detected inside the hemocoel. In addition, the larvae were macerated to assess the activity of PO using L-DOPA conversion, and the expression of antimicrobial peptides (AMPs) was measured using quantitative Real-Time PCR. The hemolymph was collected to determine changes in total hemocyte concentration (THC), the dynamics of hemocytes, and to observe hemocyte-fungus interactions.
After 24 and 48 h, scanning electron microscopy (SEM) was conducted on the larvae. Larvae were exposed to blastospores or conidia of B. In addition, other cellular and humoral responses were evaluated. Here, we assessed the invasion of the EPF Beauveria bassiana into Aedes aegypti larvae and changes in the activity of phenoloxidase (PO) as a proxy for the general activation of the insect innate immune system. Entomopathogenic fungi (EPF) have demonstrated potential as a bioinsecticide.
However, many cases of insecticide resistance have been reported. Chemical insecticides are currently employed against mosquitoes. Mosquito-borne diseases affect millions of people.
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