Expression of Bacillus thuringiensis toxin Cyt2Ba in the entomopathogenic fungus Beauveria bassiana increases its virulence towards Aedes mosquitoes

Abstract

Background The entomopathogenic fungus Beauveria bassiana has been widely used to kill mosquito larvae and adults in the laboratory and field. However, its slow action of killing has hampered its widespread application. In our study, the B . bassiana fungus was genetically modified to express the Bacillus thuringiensis (Bt) toxin Cyt2Ba to improve its efficacy in killing mosquitoes. Methodology/Principal findings The efficacy of the wild type (WT) of B . bassiana and a transgenic strain expressing Cyt2Ba toxin ( Bb -Cyt2Ba) was evaluated against larval and adult Aedes mosquitoes ( Aedes aegypti and Aedes albopictus ) using insect bioassays. The Bb -Cyt2Ba displayed increased virulence against larval and adult Aedes mosquitoes compared with the WT: for Ae . aegypti adults, the median lethal time (LT 50 ) was decreased by 33% at the concentration of 1× 10 8 conidia/ml, 19% at 1× 10 7 conidia/ml and 47% at 1× 10 6 conidia/ml. The LT 50 for Ae . albopictus adults was reduced by 20%, 23% and 29% at the same concentrations, respectively. The LT 50 for Ae . aegypti larvae was decreased by 42% at 1× 10 7 conidia/ml and 25% at 1× 10 6 conidia/ml, and that for Ae . albopictus larvae was reduced by 33% and 31% at the same concentrations, respectively. In addition, infection with Bb -Cyt2Ba resulted in a dramatic reduction in the fecundity of Aedes mosquitoes. Conclusions/Significance In conclusion, our study demonstrated that the virulence of B . bassiana against mosquitoes can be significantly improved by introducing the Bt toxin gene Cyt2Ba into the genome to express the exogenous toxin in the fungus. The transgenic strain Bb -Cyt2Ba significantly reduced the survival and fecundity of Ae . aegypti and Ae . albopictus compared with the WT strain, which suggested that this recombinant B . bassiana has great potential for use in mosquito control.

Endophytic Strain Bacillus subtilis 26DCryChS Producing Cry1Ia Toxin from Bacillus thuringiensis Promotes Multifaceted Potato Defense against Phytophthora infestans (Mont.) de Bary and Pest Leptinotarsa decemlineata Say

“…The median lethal time (LT50) for Ae. aegypti adults decreased by 33% at the concentration of 10 8 conidia/mL, 19% at 10 7 conidia/mL, and 47% at 10 6 conidia/mL in comparison with the wild type [ 33 ].…”

The Toxins of Beauveria bassiana and the Strategies to Improve Their Virulence to Insects

“…In brief, heterologous transgenic expression and/or fusion protein technique(s) have been successfully applied to improve fungal toxicity. Cytolytic δ-endotoxin (Deng et al, 2019b) and trypsin-modulating oostatic factors (TMOFs; Ortiz-Urquiza and are examples of heterologous transformation that improved the toxicity of insecticidal toxin genes, albeit with a suitable promoter and an expression vector. TMOF-CP, a fusion of TMOF with the tobacco mosaic virus coat protein (CP), is an example of a fusion protein approach.…”

In Vitro Inhibiting Effects of Three Fungal Species on Eggs of Donkey Gastrointestinal Strongyles

“…The dispersion of B. bassiana spores is currently studied as a means for the control of Anopheles mosquitoes, which are cyclic vectors of Plasmodium spp. [ 34 ]. When the spores of B. bassiana meet the body of susceptible arthropods, they are able to pass through the chitinous exoskeleton and enter the arthropod body, germinate, and develop, using them as a source of nourishment [ 32 ].…”