Immunological estimation of changes in the absolute amounts of nuclear RNA polymerases in strictly auxin-requiring, cultured soybean cells upon addition of 2,4-dichlorophenoxyacetic acid.

Soybean cells were subcultured in the presence of 4 μM 2,4-dichlorophenoxyacetic acid (2,4-D;=stock cells), or transferred and subcultured in a culture medium depleted of 2,4-D (=control cells), then reincubated with 4 μM 2,4-D (=treated cells). Control cells responded to 2,4-D by resuming cell division and DNA, RNA and protein synthesis at levels which were comparable to those of stock cells. This study system was used to investigate auxin effects on RNA polymerases. Both activities of RNA polymerases and their absolute amounts in extracts from stock, control and treated cells were determined, using the in-vitro assy of transcription of denatured calf thymus DNA and the specific quantitative immunological method reported in Miassod and Got (1984, Planta 162, 427-434), respectively. The data showed that the levels of enzymes did not remain constant in the stock cells during the subculture cycle, that auxin treatment enhanced, by a factor of two to four, the amounts of RNA polymerase I and II, expressed as percents of total proteins of soybean cells, and that this increase was not necessarily reflected by a parallel increase of the activity measured in the in-vitro test.