The 69 diatom MTs that are putatively derived from red algae, and red and/or green algae, clustered based on similar functions.

Shown for each cluster is the identifier (Cluster ID), number of proteins within the cluster (Size), the putative function, the classification of MT family based on TransportDB, the outgroup used in phylogeny sorting, the putative algal origin of the proteins, i.e., Red (R), Red or Green (R/G), and Red and Green (R+G), and the protein target prediction using HECTAR, in which “CHL” denotes proteins targeting to chloroplast/plastid, “MIT” denotes proteins targeting to mitochondrion, “SP” denotes presence of signal peptide, “SA” denotes presence of Type II signal anchor, “-” denotes no N-terminal target peptide found. None of these proteins show evidence of mitochondrion-targeting. The abbreviation of MT family follows Table S1, according to http://www.membranetransport.org/.