Insecticidal properties of genetically engineered baculoviruses expressing an insect juvenile hormone esterase gene

Abstract

Exploring the possibility of enhancing the properties of baculoviruses as biological control agents of insect pests, we tested the effect of expressing an insect gene (ihe) encoding juvenile hormone esterase. Juvenile hormone esterase inactivates juvenile hormone, which regulates the outcome of an insect molt. A cDNA encoding the juvenile hormone esterase of Heliothis virescens was inserted into the genome of Autographa californica nuclear polyhedrosis virus such that the gene was expressed under the control of a strong, modified viral promoter. This virus, however, naturally encodes an ecdysteroid UDP-glucosyltransferase which inactivates ecdysone, the hormone which initiates molting. Since ecdysteroid UDP-glucosyltransferase could mask the effects ofjhe expression by blocking molting entirely, jhe-expressing viruses in which the ecdysteroid UDP-glucosyltransferase gene was deleted or disrupted were constructed. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of proteins from infected cells revealed several intracellular proteins and two major secreted proteins which reacted with antibodies to authentic juvenile hormone esterase. Western blot analysis coupled with tunicamycin treatment indicated that differential glycosylation was responsible for the multiple products. Hemolymph of recombinant virus-infected fourth-instar Trichoplusia ni larvae contained levels of juvenile hormone esterase activity 40-fold higher than maximal levels found in uninfected larvae. However, little or no difference in developmental characteristics, weight gain, or time of mortality was observed between insects infected with the jhe-expressing viruses and control viruses.

Baculovirus‐induced tree‐top disease: how extended is the role ofegtas a gene for the extended phenotype?

“…We observed no difference in infectivity between AcMNPV WT and AcMNPV Degt in 3rd instar larvae of S. exigua and T. ni. This is congruent with most other studies, where no effect of absence of the egt gene on viral infectivity was found, for AcMNPV in S. frugiperda (O'Reilly & Miller 1991;Eldridge et al 1992b), in T. ni (Eldridge et al 1992a) and in S. exigua (Bianchi et al 2000), for SfMNPV in S. frugiperda (Sim on et al 2012), for LdMNPV in L. dispar (Slavicek et al 1999) and for Hear-NPV in Helicoverpa armigera (Georgievska et al 2010). Only one study found that the infectivity of AcMNPV Δegt was higher than that of AcMNPV WT, in 5th instars of T. ni (Cory et al 2004).…”

Characterization of a novel silkworm (Bombyx mori) phenol UDP‐glucosyltransferase

“…The only caveat to the use of a baculovirus system was the fact that they express EGT, which could cause false-positive assay results with ecdysteroid substrates. It was therefore necessary to generate the recombinant virus expressing Bmugt1 using an egt-parent virus [19].…”

Expression, Delivery and Function of Insecticidal Proteins Expressed by Recombinant Baculoviruses

“…Towards this end, recombinant baculoviruses have been produced that over-express the enzyme juvenile hormone esterase (JHE), which degrades JH in the hemolymph [ 70 ]. While viruses expressing the native JHE from H. virescens exhibited no increase or a slight increase in speed of kill [ 26 , 71 , 74 ], mutant forms of JHE showed enhancements in feeding suppression, lethality and speed of kill when inserted and expressed in a baculovirus [ 29 , 31 , 72 , 73 ].…”