Cytokinin synthesis genes

The second and main biosynthetic pathway of cytokinins in plants is de novo synthesis from phosphorylated adenosine and a precursor of the side chain. Fig. (2). The first and for a long time the only known genes encoding cytokinin de novo synthesizing enzyme, adenylate dimethylallyltransferase (EC 2.5,1.27) also called isopentenyltransferase... 

A final exciting approach is to introduce into plants the genes for overproduction of a hormone, or antisense genes for an enzyme involve in hormone synthesis. These transgenic plants have already provided us with important information about the biological roles of auxins, cytokinins and ethylene [32]. 

Other processes involve an antagonistic action of auxin vs. cytokinin as well. For example, studies with transgenic plants containing genes for enhanced synthesis of either auxin or cytokinin has shown that both apical dominance and xylem development depend on the relative amounts of these hormones [32]. Enhanced auxin increases apical dominance and xylem formation, while enhanced endogenous cytokinin promotes the outgrowth of lateral buds, leading to a more branched plant, and decreased xylem development. 

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