Dimerization of GTR1 regulates their plasma membrane localization.

Members of the nitrate transporter 1/peptide transporter family (NPF) are multifunctional transporters of various compounds including plant hormones and play important roles in plant growth and responses to environmental stress. Recently, we found that Arabidopsis GTR1 (also known as NPF2.10) takes up gibberellic acid and jasmonoyl-L-isoleucine in addition to glucosinolates. For normal plant growth, GTR1 is regulated at the gene expression level; however, it is unclear whether post-translational regulation also occurs. Here, we found that dimerization of GTR1, possibly induced by dephosphorylation of the Thr residue located between the possible transmembrane regions, regulates its plasma membrane localization, leading to transport of glucosinolates and gibberellic acid in Xenopus oocytes. These findings suggest that dimerization of multifunctional transporters contributes to their activities at the plasma membrane.