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Title of Thesis

Mohsin A. Zaidi
Institute/University/Department Details
University Of Punjab/ National Center Of Excellence In Molecular Biology
Molecular Biology
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
novel bt proteins, bt toxin, tissue-specific promoter, mz7860, camb786

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.

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1621.14 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
114.12 KB
2 1 Introduction 1
298.37 KB
  1.1 Literature Review 5
  1.2 Goals Of Present Thesis Research 24
3 2 Materials And Methods 26
327.45 KB
  2.1 Screening Microbial Collections To Search For Novel Bt Proteins 26
  2.2 Deploying Known Bt Toxin With Tissue-Specific Promoter 46
4 3 Results 54
429.51 KB
  3.1 Screening Microbial Collections To Search For Novel Bt Proteins 54
  3.2 Deploying Known Bt Toxin With Tissue-Specific Promoter 83
5 4 Discussion 91
184.08 KB
  4.1 Screening Microbial Collections To Search For Novel Bt Proteins 91
  4.2 Deploying Known Bt With Tissue-Specific Promote 99
  4.3 Future Directons 104
6 5 Reference 105
282.1 KB
7 6 Appendix 124
171.12 KB