Cloning of acryIIIA endotoxin gene ofBacillus thuringiensis var.tenebrionis and its transient expression inindica rice

Abstract

Damage caused to rice production by coleopteran insects like rice weevil (Sitophilus oryzae), a stored grain insect pest and rice hispa (Dicladispa armigera), a pest of the growing plant is quite high. In order to combat the damage, generation of insect resistant transgenic rice plant was considered desirable. CryIIIA endotoxin of Bacillus thuringiensis var. tenebrionis, a 65 kDa protein toxic to coleopteran insects, figured as the candidate gene product. Thus, the cryIIIA gene was isolated from a local isolate of Bacillus thuringiensis var. tenebrionis. The gene was tailored at the N-terminal end to its minimal size by using a synthetic ATG codon which replaced the first codon next to ATG of threonine to proline. This modification did not affect the functional property of the gene product. A chimeric construct of the modified cryIIIA gene was developed containing CaMV35S promoter and nos terminator for plant expression. The expressibility of the cryIIIA gene in indica rice was judged through test for transient expression in indica rice protoplasts.