Differential accumulation of miRNAs in microarray and sequence assays. (a) Hierarchical cluster analysis of miRNA expression variation in leaves (L), fibers (F; +7 DPA) and fiber-bearing ovules (O+; +3 DPA) of TM-1 and ovules without fibers (O-; +3 DPA) of the N1N1 mutant (N1). At, Arabidopsis thaliana; Gm, Glycine max; Mt, Medicago truncatula; Os, Oryza sativa; Pp, Physcomitrella patens; Pt, Populus trichocarpa; Sb, Sorghum bicolor; So, Saccharum officinarum; Zm, Zea mays. Vertical lines indicate similar expression patterns of miRNAs in 'blocks'. (b) Positive correlation of miRNAs between sequencing frequencies and microarray hybridization intensities detected in cotton leaves (R2 = 0.28; P = 0.02; degrees of freedom (df) = 16). (c) Positive correlation of miRNAs between sequencing frequencies and microarray hybridization intensities detected in cotton ovules (+ 3 DPA; R2 = 0.20; P = 0.06; df = 16).