ABSTRACT
A CryV-type protein (CGCryV) has been isolated from supernatant fluids of Bacillus thuringiensis AB88 cultures. Previous reports have suggested the cryptic nature of the cryV-type genes on the basis of the absence of CryV-type proteins in parasporal crystals. The CryV-type protein reported here is expressed early in stationary phase, and evidence indicates that it is an exported protein. Analysis of the deduced protein sequence from this gene reveals the presence of an N-terminal domain that likely acts as a signal peptide. The CGCryV protein is the first reported case of a delta-endotoxin being a secreted protein, which may influence the biological relevance of these proteins.
Subject(s)
Bacillus thuringiensis/genetics , Bacterial Proteins/genetics , Bacterial Toxins , Endotoxins/genetics , Genes, Bacterial , Amino Acid Sequence , Animals , Bacillus thuringiensis/chemistry , Bacillus thuringiensis/growth & development , Bacillus thuringiensis Toxins , Bacterial Proteins/metabolism , Base Sequence , Cloning, Molecular , Coleoptera , DNA, Bacterial , Endotoxins/metabolism , Gene Expression , Hemolysin Proteins , Lepidoptera , Molecular Sequence DataABSTRACT
Recombinant nuclear polyhedrosis viruses (NPVs) expressing insect-selective toxins, hormones, or enzymes could enhance their insecticidal properties. We have constructed a recombinant, polyhedrin-positive Autographa californica NPV (AcNPV) that is orally infectious and expresses an insect-selective toxin (AaIT), isolated from the scorpion Androctonus australis, under the control of the p10 promoter. Bioassays with the recombinant baculovirus on 2nd instar larvae of Heliothis virescens demonstrated a significant decrease in the time to kill (LT50 88.0 hours) compared to wild-type AcNPV (LT50 125 hours). Production of AaIT was confirmed by western blot analysis of larval hemolymph from infected H. virescens, and bioassays with larvae of Sarcophaga falculata.