Sequence analysis of the predicted CgOpt1 protein. A. Multiple alignments (ClustalW) of the CgOpt1 SPYxEVRxxVxxxDDP motif with the motif in OPTs from yeasts, filamentous fungi, and plants. B. Topology prediction of the CgOpt1 protein. Transmembrane-domain prediction and topology representation were obtained with SOSUI . Transmembrane domains were also supported by TMHMM analysis [31, 32]. C. Unrooted phylogenetic tree of fungi and plants with predicted OPTs or OPT-like proteins. CgOPT1 sequence is represented by its species name, C. gloeosporioides, highlighted in a gray box. Sequences of proteins belonging to the PTR2 peptide transporter family were used as an out group and are termed PTR2. For species names and sequence accession numbers see Additional files 1 and Additional file 2.