Phylogenetic tree illustrating the distribution of 2,3-oxidosqualene cyclases in plants, algae, and protists.

The distance between each sequence was calculated using the program CLUSTAL W. The phylogenetic tree was drawn using Phylodendron online tool (http://iubio.bio.indiana.edu/treeapp/treeprint-form.html). Scale represents 0.1 amino acid substitutions per site. Protein clusters are enhanced by colors as follows: red and orange, β-amyrin and promiscuous β-amyrin synthases, dark red, lupeol synthases; blue, plant lanosterol synthases; green, plant cycloartenol synthases; brown, cycloartenol synthases from algae or a planctomycete, and yellow, cycloartenol synthases from protists. Abbreviations and accession numbers are given in Table S1. All proteins displayed in the phylogenetic tree have either been functionally characterized or genome annotated (except CAS1 from Salpingoeca sp, Allium macrosternom, Avena strigosa, Avena ventricosa and Luffa cylindrica, which have been annotated based on sequence homology and/or expression evidence).