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

Entomopathogenic fungi represent promising eco-friendly bioinsecticides, but are hindered by low virulence and host immunity. Here, we engineer a novel immune-evasion mechanism by exploiting the host's own pathogen recognition system. The insect β-1,3-glucan recognition protein 1 (βGRP1), containing a β-glucan-binding CBM39 domain and a glycoside hydrolase (GH16) domain, was identified as a key immune activator in insects. Silencing GmβGRP1 in Galleria mellonella significantly increased susceptibility to Beauveria bassiana. We engineered B. bassiana to secrete a catalytically inactive GmβGRP1 variant (GH16-deficient GmβGRP1cbm) that preemptively binds fungal β-glucans but lacks immune-activating capacity. This engineered strain exhibited significantly accelerated killing across diverse insects and transferred enhanced virulence to Metarhizium robertsii. Mechanistic studies confirmed that GmβGRP1cbm masks fungal β-glucan epitopes, preventing recognition and downstream immune activation. This "stealth" strategy─hijacking host immunity through preemptive occupation with decoy proteins─provides a paradigm shift toward next-generation bioinsecticides combining efficacy with environmental sustainability.