Characterization of a baculovirus gene encoding a small conotoxinlike polypeptide

Abstract

We identified a gene of Autographa californica nuclear polyhedrosis virus (AcMNPV) that encodes a small cysteine-rich polypeptide which has size and sequence similarity to omega-conotoxins, a class of calcium ion (Ca2") channel inhibitors, found in the venom of cone snails. Transcriptional analysis indicated that the 159-bp open reading frame, which we named cdl, and a downstream 984-bp open reading frame are transcribed as a single 1.3-kb bicistronic late RNA. The mature ctl gene product was identified as a small secreted protein by high-pressure liquid chromatography fractionation of extraceliular fluid. Viruses with a site-specific deletion in ctl appeared normal with regard to the kinetics and virulence of infection, both in vitro and in vivo. Although we studied the behavior of wild-type and mutant virus-infected insects in some detail, a biological role for ctl in AcMNPV infection remains to be established. * Corresponding author. that the gene product is a small, secreted peptide. The gene is not required for viral infection or replication in vitro or in vivo. We did not observe any difference in the behavior or development of wild-type (wt) or mutant virus-infected insects, and the biological function of ctl remains unknown. MATERIALS AND METHODS Cells and virus. AcMNPV Li (24) was propagated in Spodoptera frugiperda IPLB-SF21 cells (51) as previously described (29). The cells were maintained at 27°C in TC100 medium (GIBCO/BRL, Grand Island, N.Y.) supplemented with 10% fetal bovine serum and 0.26% tryptose broth. RNA isolation. Total RNA was isolated by the guanidinium isothiocyanate method (14) from wt-or AcAINPV-infected SF21 cells. Virus (20 PFU per cell) was allowed to adsorb to cells (107/100-mm plate) for 1 h at room temperature before

The Effect of a Small Conotoxin-Like ctx Gene from Autographa californica Nuclear Polyhedrosis Virus (AcMNPV) on Insect Hemolymph Melanization

“…e ctx gene was initially found in AcMNPV with a conserved structure similar to omega-conotoxins from cone snails (Eldridge et al, 1992). Despite substantial homology between BmNPV and AcMNPV, we did not detect the ctx sequence in the BmNPV genome.…”

“…e AcMNPV ctx gene was identified as a small cysteine-rich polypeptide (53 aa). Its size and sequence are similar to omega-conotoxins, a class of calcium ion channel inhibitors found in the venom of cone snails (Eldridge et al, 1992). Transcriptional assays and product purification of the ctx gene by highpressure liquid chromatography fractionation demonstrated that ctx was expressed during the baculovirus infection, but the biological role for ctx in AcMNPV infection remains unknown.…”

Gene organization and sequencing of the Choristoneura fumiferana defective nucleopolyhedrovirus genome

“…Cfdef99 (iap-4, 114 nt) was significantly shorter than op106 (iap-4, 357 nt). Neonate or late instar S. frugiperda larvae infected with a wild-type AcMNPV or a ctl-1 knockout mutant, showed no differences in mortality, motility or weight gain suggesting ctl-1 is not an essential gene (Eldridge et al, 1992). AcMNPV has a ctl-1, OpMNPV and LdMNPV have ctl-1 and ctl-2 while CfDEFNPV lacks both.…”

Genome of the most widely used viral biopesticide: Anticarsia gemmatalis multiple nucleopolyhedrovirus

“…For that reason, we named this gene ctl-2 (Table 1). OpMNPV also harbours the ctl-1 gene, which has high levels of similarity to the ctl gene of AcMNPV (Eldridge et al, 1992). The ctl gene is also present in the genome of other NPVs, GVs and entomopoxviruses.…”