PROMOTER TAGGING WITH A PROMOTERLESS IPT GENE LEADS TO CYTOKININ-INDUCED PHENOTYPIC VARIABILITY IN TRANSGENIC TOBACCO PLANTS - IMPLICATIONS OF GENE DOSAGE EFFECTS
PROMOTER TAGGING WITH A PROMOTERLESS IPT GENE LEADS TO CYTOKININ-INDUCED PHENOTYPIC VARIABILITY IN TRANSGENIC TOBACCO PLANTS - IMPLICATIONS OF GENE DOSAGE EFFECTS
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DOI：
10.1046/j.1365-313x.1994.6060879.x
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发表时间：
1994-12-01
期刊：
影响因子：
7.2
通讯作者：
SCHMULLING, T
中科院分区：
文献类型：
--
作者：
HEWELT, A;PRINSEN, E;SCHMULLING, T
烟草植株已经被转化到T-DNA结构中，该T-DNA结构中含有一个接近正确T-DNA边界的无启动子的细胞分裂素合成IPT基因。85个转基因克隆中有18个表现出典型的细胞分裂素产生增强的表型变化。Northern印迹分析证实，标签植物启动子激活了导入基因的转录活性。在转基因组织中，细胞分裂素(以玉米素核苷当量表示)的浓度增加了七倍。这些细胞分裂素水平的增加导致了重大的发育变化。转基因无性系表现出不同程度的一般细胞分裂素综合征的特征，即根生长减慢，顶端优势降低，叶表面积减小，茎生长减慢，叶片衰老延缓，或表现出细胞分裂素诱导的局部和发育特异性的改变。这些特征特别是在开花前或开花时所有腋芽休眠的同时打破，或次生分生组织或终末分化细胞的发育路径的重新定位。这表明内源性细胞分裂素的不同生长参数有可能改变分化模式。结果表明，通过启动子标签方法可以获得由于细胞分裂素普遍或局部过度生产而导致的稳定遗传的发育改变。纯合子植物中基因剂量效应的研究解释了细胞分裂素对植物发育程序影响的阈值水平的问题。
Tobacco plants have been transformed with a T-DNA construct harboring a promoterless cytokinin-synthesizing ipt gene close to the right T-DNA border. Eighteen out of 85 transgenic clones displayed phenotypic alterations typical for an enhanced cytokinin production. Northern blot analysis confirmed the transcriptional activation of the introduced gene by tagged plant promoters. The concentration of cytokinins, expressed as zeatinriboside equivalents, was increased up to sevenfold in transgenic tissues. These increases in cytokinin levels resulted in major developmental changes. Transgenic clones exhibited to different levels traits of a general cytokinin-syndrome, i.e. reduced root growth, reduced apical dominance, reduced leaf surface, reduced growth of the stem and retarded leaf senescence or displayed localized and developmentally specific cytokinin-induced alterations in otherwise normally developing plants. These traits were in particular a simultaneous break of dormancy in all axillary buds before or at the onset of flowering or the reorientation of the developmental pathway of secondary meristems or terminally differentiated cells. This indicates that endogenously produced cytokinins different growth parameters potential to alter differentiation pattern. The results show that stably inherited developmental alterations due to a general or localized cytokinin overproduction can be obtained by the promoter-tagging approach. The investigation of gene dosage effects in homozygote plants readresses the question of threshold levels for cytokinin effects on the developmental program of plants.