Timeline of appearance of class I, II, and III PABP genes during land plant evolution. The PABP genes of marine algae (C. reinhardtii), fresh water algae (K. flaccidum), the non-seed plant species P. patens and S. moellendorffii, the gymnosperm P. abies, the basal angiosperm A. trichopoda, the monocot O. sativa (rice), and A. thaliana are shown along a timeline of plant evolution from bottom to top. RRMs (green) and PABC domain (blue) are indicated. Vertical white bars represent introns in progenitor PABP genes whereas vertical red bars indicate introns in PABP genes upon appearance of specific class members. The number of genes represents the size of the PABP gene family for each species shown except P. abies where only the class I (MA_10436565), class II (MA_111003), and class III (MA_36585) genes are shown.