Construction of polyhedrin-positive recombinant virus with expression of truncated δ-endotoxin from Bacillus thuringiensis in insect cell

摘要

Baculoviruses have been widely used as biological agents because of their specific pathogenicity for target insect and harmlessness to mammals, birds and plants as well as advantages with persistence and epidemics as pestcides. A major drawback for more wide-spread use of these viruses is their low virulence and slow speed of action, which restricted their use. No enhancement in pathogenicity of recombinant viruses was observed with insertion of the Bacillus thuringiensis full-length endotoxin cryIA(c) and cryIA(b) gene into the AcNPV (Autographa califomica nuclear polyhedrosis virus) genome under the control of polyhedrin gene promoter. The reason may be that protoxin, full-length genes product of recombinant virus in infected insect cells, which was short of insect gut alkali environment, cannot be degraded into active toxic polypeptide. Expression level of 3' half part truncated cryIA(b) gene was ten times higher than that of full-length gene in transgenic plant and transgenic plants with truncated endotoxin gene only exhibit insecticidal activity; 3' half part of δ-endotoxin genes interferes with expression of itself in plant. At present, recombinant viruses with integration of foreign gene on ocu gene loci, lack polyhedra and therefore are unable to infect insect directly and cannot exist persistently in nature.