Structural variations in tobacco miR168 isoforms compared to other representative plants. (A) Variation in average length between miR168 and miR168* sequences among monocots, all dicots except Solanaceae and among Solanaceae. (B) Secondary structures of miR168 members from few plants. Although rice, soybean and Arabidopsis have 2 identical mature miR168 isoforms with almost similar secondary structures, tobacco isoforms have diverse secondary structures. RNA fold (http://rna.tbi.univie.ac.at/cgi-bin/RNAfold.cgi) was used to determine secondary structures. (C) Phylogenetic analysis of miR168 isoforms from tobacco indicating two clusters. Tree was constructed as described in methods section.