McKenzie MJ, Mett V, Jameson PE
Plant Physiol. 1998 Mar;116(3):969-77. doi: 10.1104/pp.116.3.969.
The cytokinin group of plant hormones regulates aspects of plant growth and development, including the release of lateral buds from apical dominance and the delay of senescence. In this work the native promoter of a cytokinin synthase gene (ipt) was removed and replaced with a Cu-controllable promoter. Tobacco (Nicotiana tabacum L. cv tabacum) transformed with this Cu-inducible ipt gene (Cu-ipt) was morphologically identical to controls under noninductive conditions in almost all lines produced. However, three lines grew in an altered state, which is indicative of cytokinin overproduction and was confirmed by a full cytokinin analysis of one of these lines. The in vitro treatment of morphologically normal Cu-ipt transformants with Cu2+ resulted in delayed leaf senescence and an increase in cytokinin concentration in the one line analyzed. In vivo, inductive conditions resulted in a significant release of lateral buds from apical dominance. The morphological changes seen during these experiments may reflect the spatial aspect of control exerted by this gene expression system, namely expression from the root tissue only. These results confirmed that endogenous cytokinin concentrations in tobacco transformants can be temporally and spatially controlled by the induction of ipt gene expression through the Cu-controllable gene-expression system.
植物激素细胞分裂素组调控植物生长和发育的多个方面，包括打破顶端优势释放侧芽以及延缓衰老。在这项研究中，细胞分裂素合成酶基因（ipt）的天然启动子被去除，取而代之的是一个铜可控启动子。用这种铜诱导ipt基因（Cu-ipt）转化的烟草（Nicotiana tabacum L. cv tabacum）在几乎所有产生的株系中，在非诱导条件下形态与对照相同。然而，有三个株系生长状态改变，这表明细胞分裂素过量产生，并且对其中一个株系进行的全面细胞分裂素分析证实了这一点。对形态正常的Cu-ipt转化体进行体外Cu2+处理，导致所分析的一个株系叶片衰老延迟且细胞分裂素浓度增加。在体内，诱导条件导致从顶端优势中显著释放侧芽。在这些实验中观察到的形态变化可能反映了该基因表达系统所施加控制的空间方面，即仅从根组织表达。这些结果证实，通过铜可控基因表达系统诱导ipt基因表达，可以在时间和空间上控制烟草转化体中的内源细胞分裂素浓度。
