Inactivation of the ecdysteroid UDP-glucosyltransferase (egt) gene of Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) improves its virulence towards its insect host

Abstract

Some baculovirus have been genetically modified for the inactivation of their ecdysteroid glucosyltransferase ( egt ) gene, and these viruses were shown to kill infected larvae more rapidly when compared to wild-type virus infections. We have previously identified, cloned, and sequenced the egt gene of Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV). Here we present data regarding the construction of an egt minus ( egt −) AgMNPV and its virulence towards its insect host. We have inserted an hsp70 - lacZ (3.7 kb) gene cassette into the egt gene open reading frame (ORF) and purified a recombinant AgMNPV (vAgEGTΔ- lacZ ). Bioassays with third-instar A. gemmatalis larvae showed that viral occlusion body (OB) production were consistently lower from infections with vAgEGTΔ- lacZ compared to the wild-type virus. A mean of 20.4×10 8 OBs/g/larva and 40.7×10 8 OBs/g/larva was produced from vAgEGTΔ- lacZ and AgMNPV infections, respectively. The mean lethal concentration which killed 50% of insects in a treatment group (LC 50 ) for the 10th day after virus treatment (DAT) was 3.9-fold higher for the wild-type virus compared to vAgEGTΔ- lacZ . The recombinant virus killed A. gemmatalis larvae significantly faster (ca. 1–2.8 days), than the wild-type AgMNPV. Therefore, the vAgEGTΔ- lacZ was more efficacious for the control of A. gemmatalis larvae (in bioassays) compared to wild-type AgMNPV.