Identification and characterization of plant hormone transporters by using receptor complex reconstitution systems (The JSCRP Award for the Encouragement of Young Scientists,The Society Awards Lectures)

Abstract

Studies have indicated that most of plant hormones are mobile. However, it was unclear how the transport of hormones is regulated. In this study, we developed a system to functionally identify plant hormone transporters. A yeast two-hybrid system with the abscisic acid (ABA) receptor and PP2C protein phosphatase was used to detect ABA transport activities of proteins expressed in yeast cells. We found that a member of Arabidopsis NRT1/PTR FAMILY (NPF) proteins, NPF4.6, could induce interactions between the ABA receptor and PP2C under low ABA concentrations. ABA transport activities of NPF4.6 was confirmed by directly analyzing the compound taken into yeast or insect cells by LC-MS/MS. Finally, characterization of mutants defective in NPF4.6 demonstrated that the protein functions as an ABA transporter in vivo. Interestingly, we found that NPF proteins transported not only ABA, but also gibberellin and jasmonoyl-isoleucine, suggesting that they might function as transporters of these hormones.