Cover image

Cover A circular representation of small RNA alignment frequency for 21-nt and 24-nt small RNAs along the length of each of the 12 nuclear Oryza sativa chromosomes (green), starting with the first chromosome at 12 o’clock. The yellow and orange consecutive rings represent degenerate alignments of 21-nt and 24-nt small RNAs, respectively, to the corresponding chromosomes. Small RNA alignments are nonuniform with hot spots of 24-nt sequences aligning to the heterochromatic regions, including most centromeres and some clusters of ribosomal RNA genes. The fractal trees conceptually represent our use of sequence-based hierarchical clustering and graph theory algorithms to identify novel microRNA families in Pinus contorta. (Cover illustration by Ryan Morin using Circos, fractal image created by Maia. [For details, see Morin et al., pp. 571–584.])