Aromatic dipeptide Trp-Ala can be transported by Arabidopsis peptide transporters AtPTR1 and AtPTR5.

Dipeptides with an aromatic residue at the N-terminal position induced lower inward currents or blocked leak currents in Xenopus oocytes expressing the proton-coupled peptide transporter AtPTR1 or AtPTR5 of Arabidopsis thaliana compared with dipeptides with an aromatic residue at the C-terminal position. Here, AtPTR1 and AtPTR5 were expressed in a yeast mutant of peptide transporter (ptr2) with tryptophan auxotrophy. Growth assays showed that Trp-Ala could be transported by both AtPTR1 and AtPTR5 as efficiently as Ala-Trp. Our data suggested that the previous finding in Xenopus oocytes might be an artifact of heterologous expression, and that AtPTR1 and AtPTR5 expressed in yeast could transport dipeptides with an aromatic residue at the N-terminal position.