Inactivation of the ecdysteroid UDP-glucosyltransferase (egt)geneof Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) improves its virulence towards its insect host Francisco J.R. Pinedo, a Fl avio Moscardi, b Teresa Luque, c Julie A. Olszewski, c and Bergmann M. Ribeiro a, * a Laborat orio de Microscopia Eletr^ onica e Virologia, Departamento de Biologia Celular, Universidade de Bras  ılia, CEP 70910-900, Bras  ılia, DF, Brazil b Embrapa-Soja, C.P. 231, CEP 86001-970, Londrina, Paran a, Brazil c Department of Biological Sciences, Imperial College of Science, Technology and Medicine, London SW7 2AZ, UK Received 6 August 2002; accepted 16 January 2003 Abstract Somebaculovirushavebeengeneticallymodifiedfortheinactivationoftheirecdysteroidglucosyltransferase(egt)gene,andthese 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))AgMNPVanditsvirulencetowardsitsinsecthost.Wehaveinsertedan hsp70-lacZ (3.7kb)gene cassette into the egt gene open reading frame (ORF) and purified a recombinant AgMNPV (vAgEGTD-lacZ). Bioassays with third- instar A. gemmatalis larvae showed that viral occlusion body (OB) production were consistently lower from infections with vAgEGTD-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 vAgEGTD-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 vAgEGTD-lacZ. The recombinant virus killed A. gemmatalis larvae significantly faster (ca. 1–2.8 days), than the wild-type AgMNPV. Therefore, the vAgEGTD-lacZ was more efficacious for the control of A. gemmatalis larvae (in bioassays) compared to wild-type AgMNPV. Ó 2003 Elsevier Science (USA). All rights reserved. Keywords: Baculovirus; Anticarsia gemmatalis; Velvetbean caterpillar; Genetic engineering; Biological control; Ecdysteroid glucosyltransferase 1. Introduction The Baculoviridae is a family of large double-stran- ded DNA viruses that infects invertebrates. This family is composed of two genera: Nucleopolyhedrovirus (NPV) and Granulovirus (GV).NPVsareinfectioustoinsectsof different orders, such as Lepidoptera, Hymenoptera, and Diptera (Blissard and Rohrmann, 1990). This virus group infects insects with high specificity producing two infectious phenotypes. The extra-cellular or budded vi- rus is produced early in the infection cycle and is re- sponsible for the dissemination of infection from cell to cell inside the insect host. The other phenotype is pro- duced late in infection, and results from occlusion of virions into protein bodies in the nuclei of infected cells. This form of the virus is called an occlusion body (OB) or polyhedra and is responsible for the dissemination of the virus from insect to insect in the environment. AcMNPV is considered the prototype baculovirus and its genome has been completely sequenced (Ayres et al., 1994). Anticarsia gemmatalis multiple-embedded nucleopolyhedrovirus (AgMNPV) was isolated from dead A. gemmatalis H€ ubner larvae in Brazil in the 1970s (Allen and Knell, 1977; Carner and Turnipseed, 1977; Corso et al., 1977). A. gemmatalis is the main defoliator of soybean and is responsible for over half of the amount of chemical insecticides used in soybean fields. Since the early 1980s, AgMNPV has been used to Biological Control 27 (2003) 336–344 www.elsevier.com/locate/ybcon * Corresponding author. Fax: +55-61-4476533. E-mail address: bergmann@unb.br (B.M. Ribeiro). 1049-9644/03/$ - see front matter Ó 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S1049-9644(03)00026-4