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Engineered fungus containing a caterpillar gene kills insects rapidly by disrupting their ecto- and endo-microbiomes
Song Hong1,2, Hanchun Gao1,2, Haimin Chen3
1Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China.
Abstract:
Similar to the physiological importance of gut microbiomes, recent works have shown that insect ectomicrobiotas can mediate defensive colonization resistance against fungal parasites that infect via cuticle penetration. Here we show that engineering the entomopathogenic fungus Metarhizium robertsii with a potent antibacterial moricin gene from silkworms substantially enhances the ability of the fungus to kill mosquitos, locusts, and two Drosophila species. Further use of Drosophila melanogaster as an infection model, quantitative microbiome analysis reveals that engineered strains designed to suppress insect cuticular bacteria additionally disrupt gut microbiomes. An overgrowth of harmful bacteria such as the opportunistic pathogens of Providencia species is detected that can accelerate insect death. In support, quantitative analysis of antimicrobial genes in fly fat bodies and guts indicates that topical fungal infections result in the compromise of intestinal immune responses. In addition to providing an innovative strategy for improving the potency of mycoinsecticides, our data solidify the importance of both the ecto- and endo-microbiomes in maintaining insect wellbeing.
Insights
Engineering fungi with antibacterial genes boosts insecticidal effectiveness against mosquitos and locusts. This approach also impacts insect gut microbiomes, highlighting the importance of both external and internal microbial communities for insect health.
Area of Science:
- Entomology
- Microbiology
- Genetics
Background:
- Insect ectomicrobiotas confer resistance against fungal cuticle pathogens.
- Gut microbiomes are crucial for host physiology and immunity.
Purpose of the Study:
- To enhance the insecticidal efficacy of the fungus Metarhizium robertsii.
- To investigate the impact of engineered fungi on insect microbiomes and host immunity.
Main Methods:
- Genetic engineering of Metarhizium robertsii with a silkworm moricin gene.
- Infection assays on mosquitos, locusts, and Drosophila species.
- Quantitative microbiome analysis and antimicrobial gene expression studies in Drosophila melanogaster.
Main Results:
- Engineered M. robertsii showed enhanced lethality against tested insect species.
- Suppression of cuticular bacteria by engineered fungi disrupted gut microbiomes, leading to harmful bacterial overgrowth (e.g., Providencia species).
- Fungal infections compromised intestinal immune responses in Drosophila.
Conclusions:
- Engineering entomopathogenic fungi with antibacterial genes is a promising strategy to improve mycoinsecticide potency.
- Both ecto- and endo-microbiomes play critical roles in insect defense and overall well-being.
- Disruption of insect microbiomes can have detrimental consequences for host survival.
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