Abstract
EcR (ecdysone receptor)-mediated ecdysone signaling pathway contributes to regulate the transcription of genes involved in various processes during insect development. In this work, we detected the expression of EcR gene in silkworm ovary-derived BmN4 cells and found that EcR RNAi result in an alteration of cell shape, indicating that EcR may orchestrate cell cycle progression. EcR RNAi and EcR overexpression analysis revealed that in the cultured BmN4 cells, EcR respectively promoted and suppressed the transcription of E2F-1 and CycE, two genes controlling cell cycle progression. Further examination demonstrated that ecdysone application in BmN4 cells not only changed the transcription of these two cell cycle genes like that under EcR overexpression, but also induced cell cycle arrest at G2/M phase. In vivo analysis confirmed that E2F-1 expression was elevated in silk gland of silkworm larvae after ecdysone application, which is same as its response to ecdysone in BmN4 cells. However, ecdysone also promotes CycE transcription in silk gland, and this is converse with the observation in BmN4 cells. These results provide new insights into understanding the roles of EcR-mediated ecdysone signaling in the regulation of cell cycle.
Highlights
IntroductionEcdysone receptor (EcR), as a member of nuclear receptor family, was identified and well-characterized in insects and primarily contributes to meditate the signaling of steroid hormone ecdysone [1,2,3]
Quantitative RT-PCR examination confirmed an obvious expression of Ecdysone receptor (EcR) gene in BmN4 cells (Figure 1B)
Together with the observation that EcR expression could be detected in cultured mosquito (Aedes albopictus) cells [32], we speculated that EcR may be involved in cell cycle or cell growth in cultured cells without the existence of ecdysone
Summary
Ecdysone receptor (EcR), as a member of nuclear receptor family, was identified and well-characterized in insects and primarily contributes to meditate the signaling of steroid hormone ecdysone [1,2,3]. It is conservation among multicellular organisms that cyclin E (CycE) and its CDK partner Cdk are responsible for initiating the G1/S transition by promoting DNA replication [17], and CycB interacts with Cdk to promote the G2/M transition by triggering mitosis [18,19]. BmN4-SID1 cells, indicating that EcR may be involved in the regulation of the transcription of cell cycle genes in silkworm cells. We performed RNA interference (RNAi)-mediated knockdown of EcR gene and ecdysone treatment in the silkworm at cellular and individual scales, and found that EcR-mediated ecdysone signaling can regulate the transcription of two cell cycle genes, E2F-1 and CycE
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