Integration of an insecticidal scorpion toxin (BjαIT) gene into Metarhizium acridum enhances fungal virulence towards Locusta migratoria manilensis

Abstract BACKGROUND Entomopathogenic fungi have been developed as biopesticides, but poor efficacy has blocked their application. One approach to improving virulence is by genetic manipulation. Bjα IT from the venom of Buthotus judaicus is an insect‐selective neurotoxin. To clarify the insecticidal potency of Bjα IT as a virulence candidate in microbial biocontrol agents, the entomopathogenic fungus Metarhizium acridum was genetically modified with Bjα IT , and its resulting activity against locusts ( Locusta migratoria manilensis ) was assessed. RESULT In comparison with the wild‐type strain, the engineered isolate Bjα IT ‐102 grew significantly quicker in locust haemolymph. Correspondingly, the median lethal dose ( LC 50 ) for Bjα IT ‐102 was 18.2‐fold lower, and the median lethal times ( LT 50 ) for Bjα IT ‐102 were reduced by 28.1 and 30.4%, respectively, after topical inoculation and injection. Bjα IT ‐102 formed conidia on dead locusts, although the conidial yield was reduced 1.58‐fold. Moreover, there were no significant differences in germination and appressorium formation between the Bjα IT ‐102 and wild‐type strains. CONCLUSION Expression of Bjα IT in M. acridum significantly increased virulence against locusts by shortening the in vivo infection period without affecting conidium formation on the carcasses. This study demonstrated that engineering entomopathogenic fungi to incorporate Bjα IT offers great potential for increasing their virulence. © 2014 Society of Chemical Industry