Abstract: 【Aim】 Ras signaling pathway palys an important role in cell proliferation and growth in Drosophila. Myc, a member of basic helix-loop-helix (bHLH) transcription factor family, regulates physiological processes such as cell growth, competition and tissue regeneration. The aim of this study is to clarify the interaction between Ras signaling and Myc, and to explore the mechanism how Ras signaling regulates the growth of endoreplication cells. 【Methods】 The transcription level of Myc in posterior silk glands of transgenic silkworm (Bombyx mori) was analyzed by bioinformatics tools and detected by qPCR. Ras^V12 or Raf wereoverexpressedby transfecting pAc5.1-HisB-Ras^V12-V5 or pAc5.1-HisB-Raf-Flag plasmid into Drosophila melanogaster Kc cells, respectively, and the mRNA and protein expression levels of Myc were detected by qPCR and Western blotting, respectively. The functions of Ras signaling in regulation of Myc in larval fat body and salivary glands of D. melanogaster were verified by using D. melanogaster genetic tools and molecular biology methods. 【Results】 Overexpression of Ras1CA in silkworm posterior silk glands up-regulated Myc transcriptional level. Activation of Ras signaling up-regulated Myc expression at both the transcriptional and protein levels in D. melanogaster Kc cells. In salivary glands and fat body of D. melanogaster larva, the expression levels of Myc at the wandering stage were higher than those at the feeding stage. Overexpression of Myc or activation of Ras signaling accelerated endocycling. Activating Ras signaling promoted Myc expression.【Conclusion】 The Ras signaling pathway can activate the expression of Myc, thereby accelerating the endocycle and promoting organ development.

Key words: Drosophila melanogaster, Bombyx mori, salivary gland, fat body, Ras signaling pathway, Myc, endocycle