Differences in isoform frequency between two individuals. (A). Scatter plot showing all long isoform (intron retention) AS frequencies between two individuals (PT17 and PT18). Each point represents an intron retention event. (B). An example of significant isoform variation in RNA specific to Poptr_0002s21650 (predicted to encode a glycoside hydrolases family 9 protein) between PT17 and PT18 and RT-PCR validation of Poptr_0002s21650 isoform frequency variation in PT17 and PT18. The migration of PCR products corresponding the long (L, intron retention) and short (S) isoforms by gel electrophoresis is shown, with the relative frequencies was estimated by RNA-Seq data.