Fig. 1

Structural and functional analyses of the 39 K promoter a Schematic of Firefly luciferase and Renilla luciferase expression vectors used for the dual luciferase reporter system. Luciferase activity assay of the dual luciferase reporter system. BmN-SWU1 cells were transfected with pGL3-39 K-FLUC cassettes and the luciferase reporter plasmid pGL3-IE1-RLUC, luciferase activity was measured after infection or non-infection BmNPV. The results were calculated as relative luciferase activity (i.e., Firefly luciferase/Renilla luciferase). Assays were performed in triplicate. BmNPV(+) represents infection with BmNPV, BmNPV(−) represents non-infection with BmNPV, And NS meansnot significant. Statistically significant differences. b Relative luciferase assay of the 5´-end truncated of the 39 K promoter. c Relative luciferase assay deletion and truncated fragment of the 39 K promoter. d Relative luciferase assay 3´-end truncated of the 39 K promoter. Cells co-transfected with the Firefly luciferase and Renilla luciferase expression vector were infected or non-infected with BmNPV at 10 MOI. Cells were examined under luciferase reporter system at 48 h p.i.. Black represents − 773~ − 1 fragment, blue represents + 1~ + 136 fragment and dashed line represents the missing fragment of the 39 K promoter. Red represents the Firefly luciferase reporter gene. The Y axis represents different truncated promoters and the X axis represents relative promoter activity of different promoters under infectious and non-infected conditions. The results were calculated as the relative luciferase activity (i.e., Firefly luciferase/Renilla luciferase). The 39 K promoter luciferase activity represents 1 and the promoter activity of the other truncated fragment is a ratio relative to 39 K promoter. BmNPV(+) represents infection with BmNPV, BmNPV(−) represents non-infection with BmNPV