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. 1997 Aug 15;11(16):2124–2136. doi: 10.1101/gad.11.16.2124

Figure 1.

Figure 1

 (A) Brassica diploids and their derived allotetraploids. The triangle illustrates the genomic relationships among six major Brassica crop species. B. nigra is placed at the top and B. rapa is placed higher than B. oleracea to summarize our finding that the hierarchy of nucleolar dominance among the diploid species is B. nigra → B. rapa → B. oleracea. Diploid genome compositions are denoted as aa, bb, or cc. (n) Chromosome number. (B) S1 nuclease protection results revealing the dominance hierarchy depicted in A. Total RNA (20 μg) isolated from leaves of B. oleracea (O); B. carinata (C); B. nigra (Ni); B. juncea (J); B. rapa (R); and B. napus (Na) was hybridized to 5′ end-labeled probes specific for B. nigra (lanes 3–7); B. oleracea (lanes 8–12); or B. rapa (lanes 13–17) rRNA transcripts. Following S1 digestion, protected probe fragments were resolved on a sequencing gel and visualized by autoradiography. Nigra transcripts are detected in nigra, carinata, and juncea; rapa transcripts are detected in rapa and napus; oleracea transcripts are detected only in oleracea. Sequencing reactions served as size markers in lanes 1 and 2.