Cloning and characterisation of a novel holotype crystal protein gene,cry59Ba1, from Bacillus thuringiensis strain Bm59-2, toxic to Spodoptera exigua (Lepidoptera)

Abstract

A novel cry59-type gene, cry59Ba1, was obtained from isolate Bm59-2 and identified from an assembled plasmid genome sequence. This gene was found to encode a polypeptide of 674 amino acid residues with a predicted molecular mass of 75.2 kDa. This polypeptide was 62.1% identical to cry59Aa1. The Cry59Ba1 protein was expressed in the acrystalliferous mutant strain HD73^? and tested against Culex quinquefasciatus (Diptera), Spodoptera exigua (Lepidoptera) and Helicoverpa armigera (Lepidoptera). The bioassay showed Cry59Ba1 protein to be highly toxic to S. exigua (Lepidoptera) (LC50 =26.2 µg/ml, 95% confidence limit, 16.2-75.3 µg/ml). The cloning of cry59Ba1 gene may provide a novel type insecticidal resource for resolving the problem of lepidopteran insects developing resistance to the Cry1 proteins.