In mammalian animals, the expression level of GPAT1 is the highest in liver and adipose tissues. GPAT activity has closely associated with the events which require de nove TAG biosynthesis. Thus the GPAT1 transcript increases by >20-fold in mouse liver once refed with a high-carbohydrate diet after starvation. By contrast, starvation for 48 h significantly reduces GPAT1 activity in rat liver and adipose tissues. This result indicates that GPAT1 is involved in TAG biosynthesis19. Mice with GPAT1 deficiency have reduced hepatic TAG, plasma TAG and VLDL–TAG secretion21. Even after feeding with high-fat diet, mice with GPAT1 deficiency have lower plasma and liver TAG and DAG contents than wild-type mice22. Correspondingly, the liver-directed overexpression of GPAT in mouse significantly increases hepatic TAG and DAG contents by 12- and 7-fold, respectively23. These results completely elucidated the function of GPAT in TAG biosynthesis. In the present study, expression analysis of BmGPAT in PGs revealed that BmGPAT was predominantly expressed during adult stages. The RNAi-mediated knockdown of the BmGPAT gene significantly reduced PG TAG contents (Fig. 5C; Fig. 5D), bombykol production (Fig. 5E) and female ability to attract males (Fig. 6B). This result suggested that BmGPAT play an import role in TAG biosynthesis, bombykol production and subsequent mating behavior in B. mori.