PirB-Cry2Aa hybrid protein exhibits enhanced insecticidal activity against Spodoptera exigua larvae

Previous study revealed that the N-terminal region of PirB toxin from Photorhabdus luminescens showed 20.5% identity and 41.5% similarity to the domain I of Cry2A toxin of Bacillus thuringiensis. The encoding sequence of the domain I of Cry2Aa protein was replaced by the encoding gene of corresponding domain of PirB protein. Expression of pirB-cry2Aa chimeric gene in B. thuringiensis acrystalliferous strain Cry(-)B leads to the formation of crystals with irregular shape. Bioassay showed that PirB-Cry2Aa hybrid protein displayed toxicity against Spodoptera exigua and Helicoverpa armigera larvae. Our data implied that PirB protein might possess pore-forming activity and PirB-Cry2Aa hybrid protein could be used as biological control agent.