Pakistan Research Repository


Zaidi, Mohsin A (2005) CHARACTERIZATON OF A NOVEL BT PROTEIN. PhD thesis, University of the Punjab, Lahore.



In recent years, Bacillus Thuringiensis has been developed as an effective biological control against a variety of insect pests that destroy important crops. Use of this technology however, has raised concerns related to the emergence of natural insect resistance to Bacillus thllril1giellsis. To extend the use of this biocontrol resource, a detailed knowledge of the effect of Bt toxins on pests and on their resistance is required. In addition to potentially identify new Ht genes, a more complete understanding of Ht genes and factors involved during their production in dative cells would significantly improve this technology. In this study, a locally isolated Ht strain, CAMB786 toxic against sucking insects, was characterized. During characterization a new coding sequence, MZ7860, was identified from CAMB786 in addition to cry1 and cry2 coding sequences. The coding sequence MZ7860, located on the plasmid of the host strain, had no significant homology with any of the known Bt sequences in GenBank. The amino acid sequence of the putative polypeptide, MZ7860 shared 20% to 30% homology, with a few proteins, most of which were derived from bacteriophages. Protein produced from the MZ7860 coding sequence was sensitive to degradation by trypsin. This protein is produced during the vegetative stage of the host Bacillus Thuringiensis cell. The toxicity of MZ7860 was examined in a number of insects but no direct insecticidal function was established. Further investigation of this coding sequence might be helpful in elaborating the function of MZ7860 in the cellular machinery or in establishing its probable involvement in toxicity towards target pest organisms. In a parallel study, involving an additional Bt gene, tobacco Nicolial1a tabacum cv. Xal1lhi plants were transformed with clJ'2A coding sequence to express the corresponding toxin in the plant green tissues. This was achieved by using the promoter region of ST-LSI gene from potato to drive the expression of Cry2A. The accumulated levels of toxin in leaves were effective in achieving 100% mortality of Heleothis virescens larvae. Results reported here validate the use of ST-LSI gene promoter for the contained expression of Bt toxin in plants.

Item Type:Thesis (PhD)
Uncontrolled Keywords:novel bt proteins, bt toxin, tissue-specific promoter, mz7860, camb786
Subjects:Biological & Medical Sciences (c) > Biological Sciences(c1) > Biology (c13)
ID Code:401
Deposited By:Mr. Muhammad Asif
Deposited On:03 Aug 2006
Last Modified:04 Oct 2007 21:00

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