Characterization of Lepidopteran- specific Cry genes in Iranian strains of Bacillus thuringiensis

Bacillus thuringiensis (Bt) is a gram-positive and soil-dwelling bacterium commonly used as a biological toxin. After sporulation, the bacterium forms crystal proteins that are encoded by Cry genes located on the plasmid. This study aimed to identify active Cry genes against Lepidopteran in Bt bacteria isolated from soil in Eastern and Central Iran. These strains, along with two bacteria including Bt thuringiensis and Bt kurstaki as positive controls, were examined by Polymerase Chain Reaction (PCR) technique with specific primers including SPCry۱Aa, Cry۲Aa۱, Cry, Lep۲, Cry۱D, Cry۱C, Cry۲Ab۲ and Spe-Cry۸B. However, no gene was detected by the SPCry۱Aa, Cry۲Aa۱, Cry and Spe-Cry۸B primers. The results showed that the plasmid extracted from ۹۰.۹% of the isolates contained lethal genes of Lepidopteran including Cry۱A (۹۰.۹%), Cry۱D (۹۰.۹%), Cry۱C (۷۲.۷۲%) and Cry۲Ab۲ (۶۳%). The shape of crystal proteins in two native strains including ۱۰۵۳ and ۱۰۶۸, with the highest pathogenicity against Mediterranean flour moth Ephestia kuehniella (Lep.: Pyralidae), was examined by electron microscopy. The spherical and ovoid crystals for ۱۰۵۳ and diamond, bipyramidal, ovoid and cuboidal crystals for ۱۰۶۸ were identified. The native strains containing these genes can be used as commercialized biological control agents against Lepidopteran pest and to manage resistance.

کلیدواژه ها:

Plasmid ، Cry genes ، Biological toxins ، Polymerase Chain Reaction