【作者】 鞠世杰；

【导师】 阎秀峰； 王洋；

【作者基本信息】 东北林业大学 ， 生态学， 2004， 硕士

【摘要】 喜树碱(camptothecin，CPT)是喜树(Camptotheca acuminata)中的一种有抗癌活性的单萜吲哚生物碱。色氨酸合成酶(TSB)和色氨酸脱羧酶(TDC)是喜树碱合成过程中连接初生代谢和次生代谢过程的两个关键酶。本文探讨了干旱对喜树幼苗幼叶、成叶和树皮中喜树碱含量和关键酶基因(TSB和TDC)表达水平的影响，并简要分析了TSB mRNA、TDC1 mRNA、TDC2 mRNA水平与喜树碱含量变化的关系。主要结果如下： 1．干旱处理1～4天，幼叶中的喜树碱含量呈上升趋势，随后又迅速下降，到处理第6天后趋于平稳，但在处理第2天时幼叶中喜树碱含量有暂时下降的过程。干旱处理下成叶和树皮中的喜树碱含量下降。 2．在未干旱处理植株中，TSB在各个组织中都有较高水平的表达，幼叶、根、树皮和成叶中TSB mRNA含量依次减少；TDC1只在树皮中高表达，在根和幼叶中则低水平表达；而TDC2在正常植株的各组织中均不表达。 3．干旱处理下，幼叶TSB基因转录被轻微诱导并很快下降；成叶中TSB基因转录变化不明显；树皮中TSB基因转录水平仅在干旱第2天被暂时诱导，但与土壤含水率的变化没有相关性。 4．当土壤含水率在25％以上时，幼叶TDC1 mRNA水平随土壤含水率的下降而上升；当土壤含水率在25％以下时，幼叶TDC1 mRNA水平随土壤含水率的下降也下降。成叶和树皮TDC1 mRNA水平在干旱处理第4、5天时明显上升，并很快恢复到原水平。干旱处理第8、9天幼苗已经严重萎蔫时，TDC2基因才被诱导表达。更多还原

【Abstract】 Camptothecin (CPT) is an anti-cancer terpenoid indole alkaloid in Camptotheca acuminata. Tryptophan synthase (TSB) and tryptophan decarboxylase (TDC) are two key enzymes in camptothecin biosynthetic pathway as they links primary and secondary metabolism. Effect of drought on camptothecin accumulation and key enzyme genes (TSB and TDC) transcripts in young leaves, mature leaves, and bark of C. acuminata seedlings were studied, and correlations between levels of TSB mRNA, TDC1 mRNA, TDC2 mRNA and CPT content were discussed briefly. The results are as follows.In the first four days of drought treatment, CPT content in young leaves increased, but not at day 2, and then decreased quickly by day 6 to a constant level. In mature leaves and bark, the amount of CPT decreased in response to drought.In seedlings without treatment, TSB was expressed at high levels in all tissues examined. In young leaves, roots, bark and mature leaves, TSB mRNA abundance decreased sequently. TDC1 expressed at high levels only in bark. In mature leaves and roots, it expressed at low levels. The expression of TDC2 was not detected at any tissues in untreated seedlings.In young leaves, TSB expression was induced slightly, and then decreased in response to water deficit. Changes of TSB mRNA abundance in mature leaves in response to drought were not obvious. Bark TSB transcript levels were induced transiently at day 2 after no watering, but there is no correlation between it and soil water content.In young leaves, the level of TDC1 transcripts increased gradually until the soil water content reached 25% and then decreased as the soil water content decreased. The steady-state levels of TDC1 mRNA in mature leaves and bark were transiently induced at day 4 or 5. TDC2 didn’t express in all tissues examined until day 8 or 9, when the seedlings had been heavily wilted.更多还原