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

Abstract

Entomopathogenic fungi have been developed as biopesticides, but poor efficacy has blocked their application. One approach to improving virulence is by genetic manipulation. BjαIT from the venom of Buthotus judaicus is an insect-selective neurotoxin. To clarify the insecticidal potency of BjαIT as a virulence candidate in microbial biocontrol agents, the entomopathogenic fungus Metarhizium acridum was genetically modified with BjαIT, and its resulting activity against locusts (Locusta migratoria manilensis) was assessed. In comparison with the wild-type strain, the engineered isolate BjαIT-102 grew significantly quicker in locust haemolymph. Correspondingly, the median lethal dose (LC50 ) for BjαIT-102 was 18.2-fold lower, and the median lethal times (LT50 ) for BjαIT-102 were reduced by 28.1 and 30.4%, respectively, after topical inoculation and injection. BjαIT-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 BjαIT-102 and wild-type strains. Expression of BjαIT 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 BjαIT offers great potential for increasing their virulence.