Enhancement of soybean RNA polymerase I by auxin.

When etiolated soybean seedlings are treated with the synthetic auxin, 2,4-dichlorophenoxy-acetic acid, cells of the mature hypocotyl become swollen and proliferate abnormally. This abnormal growth induced by auxin coincides with a 5- to 8-fold increase in the alpha-amanitin-insensitive RNA polymerase associated with isolated chromatin or nuclei. The alpha-amanitin-sensitive RNA polymerase activity of the auxin-treated hypocotyl was similar to that of control tissue. The increase in RNA polymerase I activity of chromatin and nuclei was maintained after solubilization and fractionation on DEAE-cellulose. Auxin thus appears to enhance RNA synthetic activity (i.e., ribosomal RNA) in mature soybean tissue by altering RNA polymerase I directly rather than by altering RNA polymerase I directly rather than by altering the chromatin template.