Auxin-induced deoxyribonucleic acid dependent ribonucleic acid polymerase activities in mature soybean hypocotyl.

When 3-day-old etiolated soybean seedlings are treated with the synthetic auxin, 2,4-dichlorophenoxyacetic acid, cells of the mature hypocotyl swell and proliferate abnormally. By 48 h after auxin application ribonucleic acid (RNA) polymerase I and II levels increase by about 10-20- and 6-fold, respectively, on a fresh weight tissue basis and about 3-6- and 2-fold, respectively, on a tissue deoxyribonucleic acid (DNA) basis. [35S]Methionine incorporation into RNA polymerase subunits suggests that this increase in levels of RNA polymerases results from de novo synthesis of the enzymes. No alteration in subunit structure or patterns of incorporation of [35S]methionine into RNA polymerase subunits is detected following auxin treatment. No differences in the phosphorylation patterns of RNA polymerase subunits are detected after hormone treatment. These results indicate that although the levels of RNA polymerases I and II may regulate, in part, the rates of transcription during physiological or developmental transitions, alteration or modification of RNA polymerase subunit structure does not appear to be involved in transcriptional regulation in the auxin-induced soybean hypocotyl.