Distribution of junctions and alternative splicing events (A). Histograms of the distribution of known and new splice junctions among 20 P. trichocarpa individuals. We required splice junctions to be supported by at least two reads with a non-repetitive match position and with a minimum of four bases on both sides of the junction. (B). Histograms of the distribution of alternative splicing events among 20 individuals. Only genes with sufficient read coverage (FPKM ≥5) in all individuals were used.