Induction of apoptosis by an insect iridescent virus in boll weevil and budworm cell culture

Abstract

The cotton boll weevil, Anthonomus grandis, is a major pest of cotton, causing up to $100 million in damage to the American cotton farmer. Our laboratory has found that an insect virus (boll weevil pathogenic virus, BWPV) replicates efficiently in boll weevil larvae and a protein extract from purified virus particles induces apoptosis in cell culture. The phenomenon was confirmed in budworm (CF) and boll weevil (AG) cells by observing characteristic apoptotic cytopathology (blebbing) and DNA fragmentation. In addition, a number of differential sensitivity assays were also carried out to determine the dose required to induce blebbing and DNA fragmentation. The tissue culture toxicity dose assay (an equivalent of the LD50 assay) showed that 6.3 ng/ml is sufficient to induce apoptotic blebbing in CF cells, and 54.1 ng/ml of the virion extract is required for AG cells. Further, the minimum dose required to induce DNA fragmentation was found to be 2ug/ml. The above data will have significance for the mechanism of viral induction of apoptosis and for the use of viral genes in the generation of insect-resistant plants.