Transgenic vector construction. (A) Schematic map of the transgenic vector pBac(P25-hEGF–IE1–DsRed). pBL and pBR: sequences of the left and right arms of the piggyBac transposon, P25 promoter: the promoter sequence of the P25 gene, P25 SP: sequence of the P25 gene signal peptide, hEGF: the hEGF coding sequence, FibH polyA: the polyA signal sequence of the fibroin heavy-chain gene, hr3-IE1: combination of the hr3 enhancer and IE1 promoter to specific drive marker gene expressions in various tissues and organs of silkworms during different developmental stages, DsRed: red fluorescence protein gene, and SV40: the SV40 signal sequence. (B) Screening for positive transgenic silkworms by red fluorescence detection. (C) Chromosomal transgene insertion sites in five transgenic lines of Bombyx mori.