Amino acid-mTOR pathway-associated transcription factor GATAβ4 regulates storage protein expression in Bombyx mori.

Storage proteins (SPs) are hexameric macromolecular protein, an important component of insect serum protein, which plays a variety of roles in insect metamorphosis and development. However, their regulatory mechanisms remain unclear. Our previous studies revealed that the expression of SPs is regulated by nutritional signals and identified FoxO as a negative regulator of SPs in the silkworm Bombyx mori (B. mori). In this study, amino acids upregulated BmSP expression, whereas Rapamycin downregulated it in fat body cultured in vitro. Rapamycin also reduced BmSP expression in B. mori larvae. Overexpression of the nutrient transcription factor GATA family in BmE cells revealed that only BmGATAβ4 significantly upregulated BmSP expression. Furthermore, the amino acid-mTOR signaling pathway modulated BmGATAβ4 expression. Overexpression of BmGATAβ4 resulted in increased BmSP expression in B. mori larvae. Luciferase reporter assays, electrophoretic mobility shift assays, and chromatin immunoprecipitation identified GATA-like CRE 1-1 and GATA-like CRE 2-2 of the BmSP1 promoter as binding sites for BmGATAβ4. These findings provide new insights into the regulation of nutrient protein expression in insects.