The baculoviral transfer plasmid pVL-P12A3C was co-transfected with linearized Bm-BacPAK6 DNA into Bm-N cells by liposome-mediated method using transfection reagent lipofectamin 2000 (Invitrogen) [30] . The co-transfection supernatant was subject to plaque assays to screen the individual viral plaques. PCR amplification was conducted to confirm that the P1-2A and 3C genes had been incorporated into the baculoviral genome.