A bacmid approach to the genetic manipulation of granuloviruses.

A Cydia pomonella granulovirus (CpGV) bacmid has been constructed, which allows rapid and efficient production of recombinant baculoviruses in Escherichia coli. An 8.6kbp bacterial DNA cassette derived from the AcMNPV Bac-to-Bac system was ligated into a unique PacI restriction site within an intergenic region flanking the DNA ligase gene of the CpGV genome. The CpGV bacmids produced in E. coli were transfected into a CpGV-permissive C. pomonella cell line and the transfected cells fed to larvae to amplify the virus. The enhanced green fluorescent protein (EGFP) gene under the constitutive Drosophila heat-shock promoter was transposed into the mini-attTn7 transposition site, using a modified pFASTBAC donor plasmid, to generate a recombinant CpGV bacmid which caused infected larvae to glow under UV light. Targeted homologous recombination was also achieved in a recombinant proficient E. coli strain (BJ5183). A chloramphenicol acetyl transferase (CAT) gene replaced the cathepsin (v-cath) gene in the bacmid to produce a v-cath-deletion mutant. This is the first published report of a granulovirus bacmid, which will allow easy manipulation of the CpGV genome, enabling future studies on granulovirus genes and biology.