Cytokinin-Modulated Gene Expression in Excised Pumpkin Cotyledons

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Abstract
Comparison of 2-dimensional polyacrylamide gel electrophoretic maps of proteins isolated from benzyladenine-treated and untreated pumpkin cotyledons showed that the expression of certain proteins is enhanced, induced or suppressed by the cytokinin treatment. The amount of poly(A)+mRNA isolated from cotyledons incubated with 10-4 M benzyladenine for 5 days was .apprx. 4-fold over the water-incubated control. The activity of hydroxypyruvate reductase prepared from purified cotyledonous microbodies and analyzed by native gel electrophoresis is proportionally enhanced by sequentially higher concentrations (10-9 to 10-4 M) of benzyladenine. Ethidium bromide (1 .mu.g/ml) did not inhibit hydroxypyruvate reductase activity; the enzyme synthesis does not appear to be controlled by organelle genes. Hydroxypyruvate reductase synthesis is inhibited by cycloheximide, cordycepin and to a certain degree by actinomycin D. These data support the view of a close association between cytokinin action and gene expression.