Fig. 1

Transcriptional regulation of four BmOVO isoforms on Bmotu promoter. a Schematic of the recombinant plasmid. The basic vector is pFastBac™Dual vector. Potu represents the B. mori otu promoter; ie-1 represents B. mori nucleopolyhedrovirus immediate early-1 promoter; ovo represents four Bmovo alternative splicing isoforms of Bmovo gene; luc represents Luciferase gene; SV40pA represents Simian virus 40 (SV40) polyA signaling sequence; HSVtkpA represents the polyA signaling sequence of herpes simplex virus (HSV) thymidine kinase (TK) gene. Promoters ie1 and potu are responsible for transcription of gene Bmovo and luc respectively. b Luciferase activities in the co-transfected BmN cells with pFast-potu5-Luc-ie1-Bmovo and pRL-TK plasmids. The mixture of pFast-potu5-Luc-ie1-Bmovo (1 × 10¹¹ copies) and pRL-TK (1 × 10¹⁰ copies) plasmids were transfected into BmN cells (10⁵), and the co-transfected BmN cells with pFast-potu5-Luc (1 × 10¹¹ copies) and pRL-TK (1 × 10¹⁰ copies) plasmids was used as a control. c 1.0, 1.5 and 2.0 μg of pFast-potu5Luc-ie1-Bmovo1 plasmid was co-transfected into BmN cells (10⁵) respectively with 0.1, 0.15, and 0.2 μg of plasmid pRL-TK, and the co-transfected BmN cells with pFast-potu5-Luc(1.0 μg) and pRL-TK(0.1 μg) plasmids was used as a control. d Different combinations of pFast-potu5-Luc-ie1-Bmovo (1 × 10¹¹ copies) were co-transfected into BmN cells (10⁵) with pRL-TK (1 × 10¹⁰ copies). In various combinations, the copies of each pFast-potu5-Luc-ie1-Bmovo plasmid was 5 × 10¹⁰, and the total copies of plasmids was still 10¹¹. Luciferase activities in the cells were determined at 60 h post-transfection, 100 μg protein from the lysed cells was used for luciferase assay (*p < 0.05, **p < 0.01, ***p < 0.001)