Eukaryotic selenoproteomes. (a) A simplified cladogram of model organisms discussed in the text that illustrates distribution of selenoproteins in eukaryotes. The number of selenoproteins in each indicated model organism is shown in red (current study) and gray (previously analyzed and other model organisms) squares, and is proportional to the size of the bars on the left. Yellow circles show possible origins of various selenoprotein families, and red crosses examples of massive selenoprotein loss. (b) Selenoprotein evolution in plants. The 'mountain' symbols show terrestrial organisms, and 'anchors' those that live in aquatic environments. Green checkmarks indicate the presence of an indicated selenoprotein in the corresponding genome. The presence of Cys-containing homologs is shown by blue checkmarks. Crossed red circles indicate absence of either Sec- or Cys-containing homologs. Unfilled spots correspond to lack of data due to unfinished genomes, unclear relationship between proteins and lineage specific gene duplications.