title: Small GTPase Rab4b participates in the gene transcription of 20-hydroxyecdysone and insulin pathways to regulate glycogen level and metamorphosis.
abstract: The insulin and 20-hydroxyecdysone (20E) pathways coordinately regulate insect growth and metamorphosis. However, the molecular mechanism of the interaction of these two pathways in regulating insect development is not well understood. In the present study, we found that a small GTPase Rab4b from a lepidopteran insect Helicoverpa armigera participates in gene transcription in the two pathways. The results show that RNA interference of Rab4b in larvae results in a decrease in glycogen levels, small pupae, abnormal metamorphic transition, or larval death. The molecular mechanisms are demonstrated that knockdown of Rab4b in the larvae suppresses the transcription of glycogen synthase (GS), as well as the metamorphic-initiating factor (Br) and hormone receptor 3 (HR3), but increases the transcription of Forkhead box class O (FOXO). Further studies in the cell line confirm that Rab4b is necessary for gene transcription in the insulin and 20E pathways. Rab4b locates in the cytoplasm and takes part in regulation on FOXO cytoplasmic location by insulin induction, but travels toward the cell membrane upon 20E induction without affecting the FOXO location. The transcription of Rab4b could be upregulated by insulin injection or glucose feeding to the larvae, but not by 20E or juvenile hormone analogy methoprene. Our data suggest that Rab4b takes part in metamorphosis by regulating gene transcription and glycogen level in the insulin and 20E pathways.
authors: The Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan 250100, Shandong, China. holly86@yahoo.cn
authors: Li
authors: L
authors: Hou
authors: Mei-Juan
authors: MJ
authors: Cai
authors: Wen
authors: W
authors: Liu
authors: Qian
authors: Q
authors: Song
authors: Xiao-Fan
authors: XF
authors: Zhao
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004441:Ecdysterone / Q000378:metabolism*; D051858:Forkhead Transcription Factors / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism*; D006006:Glycogen Synthase / Q000378:metabolism; D007150:Immunohistochemistry; D007328:Insulin / Q000378:metabolism*; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D008675:Metamorphosis, Biological / Q000502:physiology*; D008969:Molecular Sequence Data; D009036:Moths / Q000254:growth & development* / Q000378:metabolism; D010802:Phylogeny; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D015398:Signal Transduction / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology*; D020695:rab4 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D051858:Forkhead Transcription Factors; D007328:Insulin; D004441:Ecdysterone; D006003:Glycogen; D006006:Glycogen Synthase; D020695:rab4 GTP-Binding Proteins