Schematic of experimental design and workflow. (A) Experimental design. Seedlings were floated on MS medium 12 hours prior to the experiment, which started on addition of 4SU. RNA was harvested concurrent with 4SU addition, and then either 1 or 2 hours later, depending on the temperature. (B) Experimental workflow for harvested samples. Samples at time 0 are extracted and hybridized directly, whereas samples at 1/2 hours are split. Total RNA is hybridized directly and compared to samples at time 0 to give change in steady state level during the labeling period. Total RNA was also split into two fractions by biotinylation and column separation, each of which is also hybridized to give abundance data for transcripts synthesized before and after 4SU addition.