Fig. 5

Application of the artificial inducible 39 K promoter. a qPCR assay of the artificial inducible 39 K (− 310~ − 355) transcriptional activation region increased promoter activity. BmN-SWU1 cells were co-transfected with indicated expression vector and infected with BmNPV at 10 MOI or uninfected. At 48 h p.i., cells were examined. Black represents 39 K(− 310~ − 355) fragment, purple represents the corresponding promoter sequence, red represents the dsred gene, dashed line represents the missing fragment of the 39 K promoter. The Y axis represents different artificial inducible promoters and the X axis represents relative promoter activity of different promoters under infected conditions. Each data point was determined from the mean of three independent replicates. NS, not significant. ** represent statistically significant differences at the level of P < 0.001. b Schematic plot of the synthetic inducible promoter