CONSTRUCTION AND CHARACTERIZATION OF IMMEDIATE-EARLY BACULOVIRUS PESTICIDES

Recombinant baculoviruses that express insect-specific toxins under th e control of viral late gene promoters can kill susceptible lepidopter an hosts faster than the wild-type virus. In an effort to improve the efficacy of genetically engineered baculovirus pesticides, we have pro duced a recombinant that contains an insect specific toxin gene (AaIT) under the control of the promoter from an immediate early gene (ie1) of Autographa californica nuclear polyhedrosis virus (AcNPV). AaIT pro tein was detected as early as 4 h postinfection in cultured insect cel ls infected with this recombinant. The protein continued to accumulate as the infection progressed and, even as late as 24 h postinfection, the amount of AaIT was about equal to that provided by a recombinant t hat expressed AaIT under the control of the very late p10 promoter. Si milar results were obtained with a recombinant that expressed a modifi ed insect juvenile hormone esterase (JHE-KK) under ie1 control, confir ming the ability of this promoter to provide early and abundant expres sion of gene products with potential pesticidal activity. Bioassays sh owed that the ie1-AaIT recombinant killed Heliothis virescens larvae f aster than wild-type virus, but not faster than the p10-AaIT recombina nt. However, larvae infected with the ie1-AaIT recombinant were smalle r than those infected with the p10-AaIT recombinant, suggesting that e xpression of AaIT earlier in infection enhanced the ability of the vir us to reduce the feeding activity of H. virescens larvae. (C) 1996 Aca demic Press, Inc.