Controlled Cytokinin Production in Transgenic
Tobacco Using a
Copper-Inducible Promoter |
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Authors: | Marian Jane McKenzie Vadim Mett Paul Hugh Stewart Reynolds Paula Elizabeth Jameson |
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Affiliation: | Botany Department, University of Otago, Private Bag 56, Dunedin, New Zealand (M.J.M.);Plant Improvement Division, The Horticulture and Food Research Institute of New Zealand, Private Bag 11030, Palmerston North, New Zealand (V.M., P.H.S.R.);Department of Plant Biology and Biotechnology, Massey University, Private Bag 11222, Palmerston North, New Zealand (P.E.J.) |
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Abstract: | 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. |
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