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Updated: Sep 30, 2026
Development of Metarhizium anisopliae as a Mycoinsecticide: From Isolation to Field Performance
Published on: July 30, 2017
Developmental and transcriptional responses to host and nonhost cuticles by the specific locust pathogen Metarhizium
Chengshu Wang1, Raymond J St Leger
1Department of Entomology, University of Maryland, College Park, MD 20742-4454, USA.
Abstract:
Transcript patterns elicited in response to hosts can reveal how fungi recognize suitable hosts and the mechanisms involved in pathogenicity. These patterns could be fashioned by recognition of host-specific topographical features or by chemical components displayed or released by the host. We investigated this in the specific locust pathogen Metarhizium anisopliae var. acridum. Only host (Schistocerca gregaria) cuticle stimulated the full developmental program of germination and differentiation of infection structures (appressoria). Cuticle from beetles (Leptinotarsa decimlineata) repressed germination while cuticle from hemipteran bugs (Magicicada septendecim) allowed germination but only very low levels of differentiation, indicating that the ability to cause disease can be blocked at different stages. Using organic solvents to extract insects we identified a polar fraction from locusts that allowed appressorial formation against a flat plastic (hydrophobic) surface. Microarrays comprising 1,730 expressed sequence tags were used to determine if this extract elicits different transcriptional programs than whole locust cuticle or nonhost extracts. Of 483 differentially regulated genes, 97% were upregulated. These included genes involved in metabolism, utilization of host cuticle components, cell survival and detoxification, and signal transduction. Surprisingly, given the complex nature of insect epicuticle components and the specific response of M. anisopliae var. acridum to locusts, very similar transcript profiles were observed on locust and beetle extracts. However, the beetle extract cluster was enriched in genes for detoxification and redox processes, while the locust extract upregulated more genes for cell division and accumulation of cell mass. In addition, several signal transduction genes previously implicated in pathogenicity in plant pathogens were only upregulated in response to locust extract, implying similarities in the regulatory circuitry of these pathogens with very different hosts.
Insights
Fungi like Metarhizium anisopliae var. acridum recognize specific host cues for infection. Locust cuticle triggers full fungal development, while other insect cuticles elicit varied responses, revealing distinct pathogenicity mechanisms.
Area of Science:
- Mycology
- Insect Pathology
- Molecular Biology
Background:
- Fungal pathogens utilize host-specific cues for infection.
- Understanding these cues informs pathogenicity mechanisms.
- Metarhizium anisopliae var. acridum is a locust pathogen.
Purpose of the Study:
- Investigate how Metarhizium anisopliae var. acridum recognizes host cues.
- Determine the role of locust cuticle in fungal development.
- Analyze transcriptional responses to host and non-host extracts.
Main Methods:
- Exposure of M. anisopliae var. acridum to different insect cuticles and extracts.
- Assessing fungal germination and appressoria formation.
- Microarray analysis of gene expression using 1,730 expressed sequence tags.
Main Results:
- Locust cuticle induced full fungal germination and differentiation.
- Beetle and hemipteran bug cuticles showed differential effects on germination and differentiation.
- Locust extract promoted appressoria formation on hydrophobic surfaces.
- Transcriptional profiles were similar for locust and beetle extracts, but locust extract upregulated cell division and mass accumulation genes.
- Beetle extract enriched detoxification and redox genes.
- Locust extract uniquely upregulated signal transduction genes relevant to plant pathogens.
Conclusions:
- Fungal pathogenicity involves complex recognition of host cues.
- Distinct transcriptional programs are activated by different insect cuticles.
- Signal transduction pathways in fungal pathogens may share regulatory circuitry across diverse hosts.
