Abstract
The administration of baculoviruses to insects for bioassay purposes is carried out, in most cases, by contamination of food surfaces with a known amount of occlusion bodies (OBs). Sinceper os infection is the natural route of infection, occluded recombinant viruses containing crystal protein genes (cry1Ab and cry1Ac) from Bacillus thuringiensis were constructed for comparison with the baculovirus prototype Autographa californica nucleopolyhedrovirus (AcNPV). The transfer vector pAcUW2B was used for construction of occluded recombinant viruses. The transfer vector containing the crystal protein genes was cotransfected with linearized DNA from a non-occluded recombinant virus. The isolation of recombinant viruses was greatly facilitated by the reduction of background "wild type" virus and the increased proportion of recombinant viruses. Since the recombinant viruses containing full-length and truncated forms of the crystal protein genes did not seem to improve the pathogenicity of the recombinant viruses when compared with the wild type AcNPV, and in order to compare expression levels of the full-length crystal proteins produced by non-occluded and occluded recombinant viruses the full-length cry1Ab and cry1Ac genes were chosen for construction of occluded recombinant viruses. The recombinant viruses containing full-length and truncated forms of the crystal protein genes did not seem to improve its pathogenicity but the size of the larvae infected with the recombinant viruses was significantly smaller than that of larvae infected with the wild type virus.
Highlights
Baculoviruses are a potential source of biopesticides for the control of insect pests
Since per os infection is the natural route of infection, occluded recombinant viruses containing crystal protein genes from Bacillus thuringiensis were constructed for comparison with the baculovirus prototype Autographa californica nucleopolyhedrovirus (AcNPV)
Since the recombinant viruses containing full-length and truncated forms of the crystal protein genes did not seem to improve the pathogenicity of the recombinant viruses when compared with the wild type AcNPV, and in order to compare expression levels of the full-length crystal proteins produced by nonoccluded and occluded recombinant viruses the full-length cry1Ab and cry1Ac genes were chosen for construction of occluded recombinant viruses
Summary
Baculoviruses are a potential source of biopesticides for the control of insect pests. Crook tal proteins are potent insecticides and exibit a very high degree of insect specificity They are produced in large amounts during sporulation of B. thuringiensis and appear as large crystals. We introduced the full-length and truncated forms of the cry1Ab gene and the full-length cry1Ac gene of Bacillus thuringiensis into the genome of the baculovirus Autographa californica nucleopolyhedrovirus (AcNPV) under the control of the polyhedrin promoter [6]. These recombinant viruses expressed the toxins and were nonoccluded. The expression of crystal proteins in insect cells and insect larvae, and the pathogenicity of recombinant viruses towards a susceptible insect were analyzed
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