Purifying selection shapes the positional distribution of incompletely excised IESs. (A) IRS-dependent changes of genomic distribution for incompletely excised IESs. (B) Expression levels of genes affected by IES retention (805 genes; IRS > 0.1, red box) and the full set of macronuclear coding genes (cyan box). The expression data are from P. tetraurelia strain d12 (two replicates, cultured at 25°C; this study). Pairwise comparison was performed with a Mann–Whitney U test. Statistical significance is indicated: (***) P < 0.01. (C) Genomic distribution of significantly retained IESs at all investigated temperatures. Distribution of PGM-IESs is shown for reference (leftmost pie chart, boxed). Sample size is indicated below each set. Percentages <5% are excluded.
