• Soumitra K Sen

      Articles written in Journal of Biosciences

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

      Tony M Johnson A S Rishi Pritilata Nayak Soumitra K Sen

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      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 ofBacillus 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 ofBacillus 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 modifiedcryIIIA gene was developed containing CaMV35S promoter andnos terminator for plant expression. The expressibility of thecryIIIA gene inindica rice was judged through test for transient expression in indica rice protoplasts.

    • High level expression of soybean trypsin inhibitor gene in transgenic tobacco plants failed to confer resistance against damage caused byHelicoverpa armigera

      Ashis Kumar Nandi Debabrata Basu Sampa Das Soumitra K Sen

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      Helicoverpa armigera is a major pest of many tropical crop plants. Soybean trypsin inhibitor (SBTI) was highly effective against the proteolytic activity of gut extract of the insect. SBTI was also inhibitory to insect growth when present in artificial diet. The gene coding for SBTI was cloned from soybean (Glycine max, CVBirsa) and transferred to tobacco plants for constitutive expression. Young larvae ofH. armigera, fed on the leaves of the transgenic tobacco plants expressing high level of SBTI, however, maintained normal growth and development. The results suggest that in certain cases the trypsin inhibitor gene(s) may not be suitable candidates for developing insect resistant transgenic plants.

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