Changes in the activity of RNA polymerase detected in situ and the intensity of 3H uridine incorporation into the nucleolus and the nucleus of interphase cells in antheridial filaments of Chara vulgaris L.

Analogously as in the 32-cell stage [20], in the 4-, and 8-cell generations of antheridial filaments of Chara vulgaris, the activity of DNA dependent RNA polymerase detected in situ as well as the 3H uridine incorporation increase in the middle S phase and in the middle G2 phase, while they decrease considerably at the end of S phase and in late G2 phase. The diphasic changes occur both in the nucleolar and extranucleolar (nucleoplasmic) activity of RNA polymerase as well as in the 3H uridine incorporation. However, the maximum nucleolar activity, in both S and G2 phases, precedes the peak of nucleoplasmic activity. During the increased nucleolar activity RNA polymerase (as calculated per nucleus) shows a higher level as compared with nucleoplasmic RNA polymerase, whereas the intensity of 3H uridine incorporation into nucleous and nucleoplasm is similar. It may be supposed that the incubation environment containing Mg2+ used in vitro is more stimulating for the nucleolar RNA polymerase than for the nucleoplasmic RNA polymerase. The mean transcriptional activity of the nucleus and the activity of RNA polymerase in the 8-cell generation is about 20% lower than in the 4-cell generation, in proportion to the decrease in cell sizes.