EBP1 RNAi transgenic plants accumulate rRNA processing intermediates. Schematic representation of the Arabidopsis full length 35S pre-rRNA transcript indicating processing sites and the position of the probes used for northern blot analysis (red bars; A) and pre-rRNA processing pathway based on Zakrzewska-Placzek at al. (2010) (B). ETS, external transcribed spacer; ITS, internal transcribed spacer. C, Ethidium bromide-stained 1% (w/v) agarose gel showing equal loading of total RNA (4 µg) from Col0 and two independent EBP1 RNAi transgenic lines 1 and 2 grown without sucrose. Molecular weight marker (M) is shown on left, and the position of the rRNAs is indicated on the right. D to G, northern blot analysis of total RNA from Col0 and EBP1RNAi lines using digoxigenin-labeled specific probes against ITS-1 (D), ITS-2 (E), 25S (F), and 18S (G), visualized by chemiluminescence. Positions of the full length pre-rRNA transcript (35S) and the processed products are indicated on the left. H, Quantification of the signal intensity of the various rRNA transcript species shown in (D) to (G). The x axis indicates the precursors and processed rRNAs, while the y axis shows relative signal intensity. Values represent means and error bars stand for se from two northern blot experiments carried out with two independent biological materials.