Fig. 4.

RNA Pol II activity in cotyledon nuclei of skoto- and photomorphogenic seedlings. (A) RNA Pol II activity was determined in individual nuclei by flow cytometry as the ratio of fluorescent signals given by double immunolabeling of the elongating (S2P) and inactive (NP) forms of RNA Pol II for each ploidy class (n > 5,000; see details in Fig. S6). Error bars correspond to SEM from two biological replicates. (B) Ploidy levels in the same samples as in A assessed by flow cytometry of DAPI-stained nuclei. (C) Representative immunolabeling signals showing the patterns of S2P (red) and NP (green) RNA Pol II forms in confocal sections of isolated cotyledon nuclei. (Scale bars, 5 µm.)