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 Basic research: We are studying insect development and metamorphosis at the cellular, organal, and organismal levels, using the fruitfly Drosophila melanogaster and the silkworm Bombyx mori as model systems. Research is focused on the molecular mechanisms of juvenile hormone and 20-hydroxyecdysone and the crosstalk of their signals.
Applied research: Insect development and metamorphosis can be used as molecular targets for both beneficial insects and pests. We are trying to improve silk quality and quantity using transgenic silkworm technique and to control the juice-sucking bugs such as planthopper using transgenic rice technique.
Principle Investigator: Dr. Sheng Li, Professor. Email: shengli@sippe.ac.cn
Staff: Rong-Jing Jiang, Research Associate; Dr. Jin-Qi Zhu, Research Assistant; Jian-Zhong Yuan, Research Assistant; Shu-Min Liu, Research Intern; Yan Liu, Research Intern; Xiao-Li Yang, Research Intern
Postdoctoral fellows: Dr. Ling Tian; Dr. Yang Liu
Graduate Students: Ying Liu; Li Ma; Shun Zhou; Sheng Wang; Han-Han Liu; Di Wen; Qian-Yu He; Jia-Wan Wang
Joint Graduate Students: En-En Guo (South China Agriculture University); Jia-Qi Zhang (Hefei Industrial University)
The bHLH-PAS Transcriptional Factor MET Sits on the Fence between Juvenile Hormone and 20-Hydroxyecdysone Signals
 20-Hydroxyecdysone (20E) and juvenile hormone (JH) are the two most important hormones to control insect development and metamorphosis. 20E determines insect molting and induces programmed cell death, while JH antagonizes 20E action. Although the signal transduction pathway of 20E is well studied, the molecular mechanism of JH action and the crosstalk between JH and 20E signals are poorly understood, mostly because the JH receptor (JHR) has not been identified. The long-standing puzzle of JH, including identifying the JHR, elucidating the JH signal transduction pathway, and dissecting out the crosstalk points between JH and 20E signals, has become the most challenging objective in the field of Entomology during the last decades.
The bHLH-PAS transcriptional factor MET was previously mistaken as a candidate JHR. Based on our most current studies, we believe MET is not a JHR although it did play an important role in the JH signal transduction pathway. In Drosophila, gce is a paralogoue gene of Met. Met/gce double mutants are pupal lethal, while Met overexpression causes programmed cell death and induces lethality at larval or pupal stages. Further studies reveal that MET sits on the fences between JH and 20E signals: when JH is present, MET inhibits 20E signal; in contrast, when JH is absent, MET promotes 20E signal. MET may form a big complex with MET, GCE, the 20E receptor EcR and USP, and FKBP39 which normally inhibits 20E signal. We are currently studying how JH changes the protein-protein interactions between MET and other molecules. JH and PKC inhibitor impact 20E signal with similar patterns. We are studying if JH inhibits PKC activity and consequently the transcriptional activity of MET. Using the response element of MET, protein-protein interaction between MET and other proteins, and PKC activity as readouts, we are going to screen the JHR with the synergism of biochemical and genetic approaches.
Publications:
Sheng ZT, Ma L, Cao MX, Jiang RJ, Li S*. (2008) Juvenile hormone acid methyltransferase is a key regulatory enzyme for juvenile hormone synthesis in the Eri silkworm, Samia cynthica ricini. Arch. Insect Biochem. Physiol. 69: 143-154. 刘影, 胜振涛, 李胜*. (2008) 保幼激素的分子作用机制. 昆虫学报 51: 974-978. Sheng ZT, Ma L, Cao MX, Li S*, Jiang RJ. ( 2007) Biochemical and molecular characterization of allatotropin and allatostatin from the Eri silkworm, Samia cynthia ricini. Insect Biochem. Mol. Biol. 37: 90-96. 刘艳, 胜振涛, 蒋容静, 黄原, 李胜*. (2007) 保幼激素合成的研究进展. 昆虫学报 50: 1285-1292. 李胜. (2007) 整合昆虫发育生物学和果蝇遗传来研究昆虫发育与变态. 昆虫知识 44: 319-322.
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