An ML phylogenetic tree of plant Su(var)3-9 SET proteins. The numbers above branches are bootstrap percentages >50, and those below are the clade name. The lowercase letter "a, b, c" represent three intronless clades. The name of Su(var)3-9 SET protein sequences is formed through species abbreviation plus SDG (SET-domain protein group) numbering. Species abbreviation: At, Arabidopsis thaliana; Os, Oryza sativa; Pt, Populus trichocarpa; Nt, Nicotiana tabacum; Vv, Vitis vinifera; Rc, Ricinus communis; Pta, Pinus taeda; Sm, Selaginella moellendorfii; Pp, Physcomitrella patens; Cr, Chlamydomonas reinhardtii. The SDG numbering for Arabidopsis thaliana and Oryza sativa are from ChromDB (http://www.chromdb.org/), and these of other species are numbered in this study. Domain type (see Table 1) within each corresponding clade is depicted on the right. Domain abbreviations: AT, AT_hook; Pre, PreSET; Post, PostSET; ZnF, ZnF_C2H2; TPR, TPR_1.