12月15日 竹田真木生:Molecular mechanism of photoperiodic clock in the Chinese oak silk moth, Antheraea pernyi


报告题目:Molecular mechanism of photoperiodic clock in the Chinese oak silk moth, Antheraea pernyi
报告人:竹田真木生  日本神户大学教授
主持人:何祝清
报告时间:12月15日 下午13:30
报告地点: 华东师大闵行校区 实验B楼511室
主办单位:生命科学学院,科技处
 
报告人简介: 竹田真木生(Takeda Makio)1978年获美国密苏里大学昆虫学博士学位,1979-1981年于特拉华大学以博士后身份研修,1982年于美国耶鲁大学以博士后身份研修,1982-1983年于荷兰瓦赫宁根农业大学以Juniour scholar身份工作,1983-1984年于日本Shionogi 制药公司以Special technical instructor身份工作,1984-1992任日本神户大学助理教授,1992-1997任日本神户大学副教授,1997年任日本神户大学教授。2007年获Japanese Society for Applied Entomology and Zoology年度论文奖。2015获日本兵库县科技奖。
 
报告内容简介:In many animals and plants, the life cycle is regulated photoperiodically for stress-hardy stages to occur in stressful seasons and growth/reproduction in favorable/permissive seasons. However, the molecular mechanism for photoperiodism remains unclarified in insects. Antheraea pernyi has been a model organism to clarify neuroendocrine switch mechanism of pupal diapause both in induction and termination since 1950’s. Short day-length induces/maintains diapause, while long-day-length stimulates pupation. Key phenomenon is whether PTTH, prothoracicotropic hormone is released or not. Lines of evidence suggested that upstream regulatory mechanism contains the indolamine regulatory pathway; (1) photoperiods affect serotonin or melatonin content in the brain, (2) these indolamines and their metabolic enzymes are co-localized in the dorsolateral neurons at juxtaposition to the circadian clock neurons, and (3) the injection of melatonin terminates pupal diapause while luzindole, an antagonist to melatonin receptor inhibited diapause termination. Photoperiodism is considered as a function of circadian system. Immunohistochemical reactivity(-ir) of circadian proteins, PER, CLK, CYC are restricted to dorsolateral neurons, thus these being circadian clock neurons, juxtaposing to serotonin receptors-, melatonin-receptor-and PTTH-ir, thus PTTH secreting neurons, We cloned these genes, identifying the enhancer E-boxes, in the upstream regulatory region of arylalakyamine N-acetyltransferase (aaNAT), suggesting that aaNAT may be a cock-controlled gene(ccg). The enzymatic activity and transcript abundance showed circadian rhythmicity. Confirmation of this link was provided by RNA interference against aaNAT, per, cyc, and clk where after dsRNA of these genes was injected, long day-length failed to terminate diapause. Transcriptional activity of regulator heterodimer Clk/ Cyc was suppressed by Per/Tim heterodimer in the circadian system in Drosophila melanogaster. If Antheraea photoperiodic/circadian system has an equivalent structure, RNAi against per should release this suppression, thus enhancing the transcription. The results strongly supported this prediction. In coclusion, circadian neurons contain indolamine metabolic machinery that affects dynamic changes in enzymatic activity thus contents of both serotonin and melatonin. Long day somehow stimulates melatonin secretion that in turn stimulates PTTH synthesis/ secretion. The PTTH neurons express two serotonin receptors and melatonin receptor. Putative melatonin receptor has 7-membrane-pass proteins that drives Ca2+ mobilization and these cells have PKC- and Rab8 (a small GPCR)-ir. What suppresses PTTH, i.e., diapause induction? Short days suppress aaNAT and thus accumulate serotonin. The key role should be played by serotonin. We have investigated dynamic change of transcription of two serotonin receptor genes, 5HTRA and B. Only the latter type responded to the exposure to short days. RNAi against 5HTRB failed to maintain diapause even under short days. This suggests that (1) critical conjunct between photoperiod and diapause is aaNAT, and two indolamine receptors, melatonin receptor and 5HTRB. The final question for Antheraea photoperiodic system is “ What constitutes the input pathway?” RNAseq provided the sequences of opsins. We investigated UVopsin, SWopsin and LWopsin on an RNAi paradigm. The injection of only SWopsin disrupted aaNAT transcription, indicating that SWopsin is the photoreceptor. This gene has two canonical E-boxes and this may constitutes the 4th interlocked negative feed-back loops. This may guarantee the robustness of the clock.