Unrooted phylogenetic tree of mTERF proteins. The tree is based on the amino acid sequences of 35 A. thaliana mTERF proteins and 23 other mTERF proteins from Chlamydomonas reinhardtii (C. reinhardtii MOC1 [Q8LJS6], MOC2 [A8IC10], mTERF1 [E1VD13], mTERF2 [E1VD14], A8IXZ5, A8JHP3), Drosophila melanogaster (D. melanogaster Q8SXK0, Q9V3F3, Q9VEB4, mTERF3 [Q06YR8]), Homo sapiens (H. sapiens mTERF1 [Q99551], mTERF2 [Q49AM1], mTERF3[Q96E29], and mTERF [Q7Z6M4]), Mus musculus (M. musculus mTERF1 [Q8CHZ9], mTERF2 [Q8BKY8], mTERF3 [Q8R3J4], Q8BVN4), Caenorhabditis elegans (C. elegans Q18746C), Plasmodium falciparum (P. falciparum Q8IBI2), Babesia bovis (B. bovis A7ARV9), Paracentrotus lividus (P. lividus Q9Y016) and Paramecium tetraurelia (P. tetraurelia A0DGH9). Green, brown and green-brown lettering depicts targeting to chloroplasts, mitochondria or dual targeting to chloroplasts and mitochondria, respectively, as reported elsewhere (Meskauskiene et al., 2009; Babiychuk et al., 2011; Quesada et al., 2011; Romani et al., 2015) and in this article. Letters in parentheses indicate predicted localization by TargetP (http://www.cbs.dtu.dk/services/TargetP) and WoLF PSORT (http://wolfpsort.org). Sequences were aligned by the ClustalW program (see Materials and Methods). The Phylip server Mobyle (see Methods) was used for phylogenetic tree constructions and comparison of distances (model: Jones-Taylor-Thornton matrix), employing a boostrap test with 1,000 replicates. Phylogenetic inference supports the existence of four main clades (I–IV). Clade I encompasses proteins encoded by a tandem gene cluster on A. thaliana chromosome 1 and several other A. thaliana mTERF proteins. In clade III, C. reinhardtii mTERFs are grouped together with animal mTERF proteins. Clade IV comprises mTERF proteins from diverse species including paramecium, sea urchin (P. livides), parasites (P. falciparum and B. bovis) together with mTERFs from Drosophila. The mTERF proteins mTERF10 and -11 (highlighted in large, bold letters) form clade I together with 25 other mTERF proteins, while mTERF12 (also highlighted in big, bold letters) is assigned to clade II, together with five other A. thaliana mTERFs and one Drosophila mTERF. C, chloroplast; M, mitochondrion; N, nucleus; Y, cytosol; O, other.