Stealth Entomopathogenic Fungi Engineered by Preemptive Occupation to Mask Host β-1,3-Glucan Recognition

Area of Science:

• Mycology
• Insect Pathology
• Biotechnology

Background:

• Entomopathogenic fungi are eco-friendly bioinsecticides but face challenges with low virulence and insect immune responses.
• Insect immune activation often involves pathogen recognition proteins binding to fungal cell wall components like beta-glucans.

Purpose of the Study:

• To engineer a novel immune-evasion mechanism for entomopathogenic fungi to enhance their bioinsecticide efficacy.
• To develop a "stealth" strategy by hijacking the insect immune system for improved pest control.

Main Methods:

• Identified and characterized insect beta-1,3-glucan recognition protein 1 (betaGRP1) as a key immune activator.
• Engineered Beauveria bassiana to secrete a catalytically inactive betaGRP1 variant (GmbetaGRP1cbm) that binds fungal beta-glucans.
• Assessed the virulence of engineered B. bassiana against various insects and its effect on Metarhizium robertsii virulence.

Main Results:

• Silencing the native betaGRP1 in Galleria mellonella increased susceptibility to B. bassiana.
• The engineered B. bassiana strain secreting GmbetaGRP1cbm exhibited significantly accelerated killing across diverse insect species.
• The engineered strain conferred enhanced virulence to Metarhizium robertsii, demonstrating a transferable virulence effect.

Conclusions:

• The engineered GmbetaGRP1cbm effectively masks fungal beta-glucan epitopes, preventing insect immune recognition and activation.
• This "stealth" strategy represents a paradigm shift for developing next-generation bioinsecticides with improved efficacy and sustainability.