A.C.L. Churchill, A. Rot, B.G.G. Donzelli and M. Samish
Fungi in the Metarhizium anisopliae complex (Hypocreales: Clavicipitaceae) include both broad and narrow host- range pathogens of arthropods. An understanding of the early interactions between pathogens and hosts that support or limit infections is necessary for efficacious deployment of entomopathogens as biological control agents of pest arthropods. We and others hypothesized that the composition of tick cuticles is a major factor determining host susceptibility to fungal infection. In in vitro studies, we demonstrated previously that cuticular compounds from resistant and susceptible ticks differentially modulate fungus development, specifically conidium germination and appressorium differentiation. In the current study, observations of GFP-expressing Metarhizium spp. that vary in virulence on tick and lepidopteran hosts demonstrated that the surface of a resistant host may support conidial germination and hyphal growth but, in contrast with growth on susceptible hosts, restricts penetration of hyphae into the hemocoel. Furthermore, cuticle from a resistant tick host appears to contain compounds that actively suppress fungal growth and survival on the tick surface, as visualized by loss of GFP expression and propidium iodide staining of hyphae. We are applying integrated, multidisciplinary approaches to test the hypothesis that tick host cuticular components modulate fungal development in vivo. These include analyses of soluble cuticular proteins, epicuticular lipids and tick pheromones effecting fungal differentiation. Additionally, expression of fungal cuticle-degrading enzymes in response to cuticle from different hosts is being evaluated. Understanding the differential induction of Metarhizium spp. virulence factors by distinct host cuticular compounds will enable better utilization of the fungus in pest control.
Abstract no. 523
A.C.L. Churchill, A. Rot, B.G.G. Donzelli and M. Samish
Fungi in the Metarhizium anisopliae complex (Hypocreales: Clavicipitaceae) include both broad and narrow host- range pathogens of arthropods. An understanding of the early interactions between pathogens and hosts that support or limit infections is necessary for efficacious deployment of entomopathogens as biological control agents of pest arthropods. We and others hypothesized that the composition of tick cuticles is a major factor determining host susceptibility to fungal infection. In in vitro studies, we demonstrated previously that cuticular compounds from resistant and susceptible ticks differentially modulate fungus development, specifically conidium germination and appressorium differentiation. In the current study, observations of GFP-expressing Metarhizium spp. that vary in virulence on tick and lepidopteran hosts demonstrated that the surface of a resistant host may support conidial germination and hyphal growth but, in contrast with growth on susceptible hosts, restricts penetration of hyphae into the hemocoel. Furthermore, cuticle from a resistant tick host appears to contain compounds that actively suppress fungal growth and survival on the tick surface, as visualized by loss of GFP expression and propidium iodide staining of hyphae. We are applying integrated, multidisciplinary approaches to test the hypothesis that tick host cuticular components modulate fungal development in vivo. These include analyses of soluble cuticular proteins, epicuticular lipids and tick pheromones effecting fungal differentiation. Additionally, expression of fungal cuticle-degrading enzymes in response to cuticle from different hosts is being evaluated. Understanding the differential induction of Metarhizium spp. virulence factors by distinct host cuticular compounds will enable better utilization of the fungus in pest control.
Abstract no. 523