ALTERATIONS OF ENDOGENOUS CYTOKININS IN TRANSGENIC PLANTS USING A CHIMERIC ISOPENTENYL TRANSFERASE GENE
ALTERATIONS OF ENDOGENOUS CYTOKININS IN TRANSGENIC PLANTS USING A CHIMERIC ISOPENTENYL TRANSFERASE GENE
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DOI：
10.1105/tpc.1.4.403
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发表时间：
1989-04-01
期刊：
影响因子：
11.6
通讯作者：
KLEE, HJ
中科院分区：
文献类型：
--
作者：
MEDFORD, JI;HORGAN, R;KLEE, HJ
细胞因子是一类植物激素，在植物发育过程中起着重要作用。我们对肿瘤银杆菌异戊烯基转移酶基因进行了遗传工程改造，将其置于热诱导型启动子（玉米hsp 70）的控制下。将嵌合hsp 70异戊烯基转移酶基因转入烟草和拟南芥植物中。转基因植物的热诱导导致异戊烯基转移酶mRNA积累并增加52倍，玉米素核苷23倍，玉米素核苷5“-单磷酸2倍。在对照温度下，转基因植物中玉米素核苷和玉米素核苷5“-单磷酸的积累水平分别是野生型植物水平的3倍和7倍。这种未诱导的细胞分裂素增加影响发育的各个方面。在烟草中，这些影响包括释放腋芽，减少茎和叶面积，以及不发达的根系。在拟南芥中，也发现了根生长的减少。然而，无论是烟草还是拟南芥转基因植物相对于野生型植物在开花时间上都没有表现出任何差异。出乎意料的是，在转基因植物中细胞分裂素的热诱导没有产生超出未诱导状态下所见的变化。缺乏热诱导增加的影响可能是细胞分裂素水平瞬时增加、直接或间接诱导阴性因子或缺乏相应水平的感受态细胞因子的结果。总体而言，在非热激转基因植物的内源性细胞分裂素水平的增加的影响似乎仅限于生长方面，而不是分化。由于细胞分裂素水平增加时程序分化模式没有改变，因此这一过程可能受绝对细胞分裂素水平以外的成分控制。
Cytokins, a class of phytohormones, appear to play an important role in the processes of plant development. We genetically engineered the Argrobacterium tumerfaciens isopentenyl transferase gene, placing it under control of a heat-inducible promoter (maize hsp70). The chimeric hsp70 is isopentenyl transferase gene was transferred to tobacco and Arabidopsis plants. Heat induction of transgenic plants caused the isopentenyl transferase mRNA to accumulate and increase the level 52-fold, Zeatin riboside 23-fold, and Zeatin riboside 5''-monophosphate twofold. At the control temperature zeatin riboside and zeatin riboside 5''-monophosphate in transgenic plants accumula to levels 3 and 7 times, respectively, over levels in wild-type plants. This uninduced cytokinin increase affected various aspects of development. In tobacco, these effects included release axillary buds, reduced stem and leaf area, and an underdeveloped root system. In Arabidopsis, reduction of root growth was also found. However, neither tobacco nor Arabidopsis transgenic plants showed any differences relative to wild-type plants in time of flowering. Unexpectedly, heat induction of cytokinins in transgenic plants produced no changes beyond those seen in the uninduced state. The lack of effect from heat-induced increases could be a result of the transient increases in cytokinin levels, direct or indirect induction of negating factor(s), or lack of a corresponding level of competent cellular factors. Overall, the effects of the increased levels of endogenous cytokinins in non-heat shocked transgenic plants seemed to be confined to aspects of growth rather than differentiation. Since no alterations in the programmed differentiation pattern were found with increased cytokinin levels, this process may be controlled by components other than absolute cytokinin levels.