Sequencing flow chart and size distribution of small RNAs in cotton. (a) Flow chat of small RNA library construction and sequencing. The plant materials included seedling leaves, dissected ovules 3 days prior to anthesis (-3 DPA), on the day of anthesis (0 DPA), and 3 days post-anthesis (+3 DPA). Red arrows indicate the location of materials harvested for RNA extraction. (b) Size distribution of small RNAs in leaves and ovules at -3 DPA, 0 DPA, and +3 DPA. High-level accumulation of 24-nucleotide small RNAs in the ovules (0 and +3 DPA) may result from overproduction of siRNAs during early stages of ovule and fiber development. Inset: total small RNA reads after removal of other cellular RNA sequences.