Mj. Mckenzie et al., CONTROLLED CYTOKININ PRODUCTION IN TRANSGENIC TOBACCO USING A COPPER-INDUCIBLE PROMOTER, Plant physiology, 116(3), 1998, pp. 969-977
The cytokinin group of plant hormones regulates aspects of plant growt
h and development, including the release of lateral buds from apical d
ominance and the delay of senescence. In this work the native promoter
of a cytokinin synthase gene (ipn was removed and replaced with a Cu-
controllable promoter. Tobacco (Nicotiana tabacum L. cv tabacum) trans
formed with this Cu-inducible ipt gene (Cu-ipt) was morphologically id
entical to controls under noninductive conditions in almost all lines
produced. However, three lines grew in an altered state, which is indi
cative of cytokinin overproduction and was confirmed by a full cytokin
in analysis of one of these lines. The in vitro treatment of morpholog
ically 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 rele
ase of lateral buds from apical dominance. The morphological changes s
een during these experiments may reflect the spatial aspect of control
exerted by this gene expression system, namely expression from the ro
ot tissue only. These results confirmed that endogenous cytokinin conc
entrations in tobacco transformants can be temporally and spatially co
ntrolled by the induction of ipt gene expression through the Cu-contro
llable gene-expression system.