An evolutionary scenario for the origin of plant PAL. A HAL coding gene (orange circle) was present in the most recent eukaryotic ancestor, based on its presence in all major eukaryotic supergroups for which sequence data is available (indicated by an asterisk), and it was lost in the ancestor of Dikarya Fungi and in the ancestor of the phylum Plantae (orange crosses). In contrast, the origin of eukaryotic PAL is more recent: (1) origin of PAL in a bacterium (green circle), (2) HGT to fungi -Dikarya or possibly earlier (solid green arrow), (3) HGT from fungi to an ancestor of land plants (dashed green arrow). Alternatively: (1) origin of PAL in a soil bacterium (green circle), (2a) HGT to an ancestor of land plants (solid pink arrow), (3a) HGT from this ancestor to fungi (dashed pink arrow). Extensive HGT of PAL and HAL among and within bacteria and archaea are indicated by double rounded arrows and gene losses by green and orange crosses.