Master student National Taiwan University Kaohsiung City, Kaohsiung, Taiwan (Republic of China)
Body of Abstract: Nitrogen is an essential nutrient for plant growth and other physiological reactions, so it is vital to reveal how plants gain and use nitrogen. NPF6.4 belongs to the nitrate transporter1/peptide transporter family (NPF) in Arabidopsis thaliana. In our previous study, NPF6.4 was reported to participate in defense responses to Pseudomonas syringae. However, less is known about the transport function of NPF6.4. To understand the physiological roles of NPF6.4, we characterized the transport activity of NPF6.4 by the oocyte expression system and the yeast complementation assay. In this research, we confirmed that the subcellular localization of NPF6.4 was in the plasma membrane. NPF6.4 transported nitrate under low and high nitrate concentrations in the oocyte expression system, indicating that NPF6.4 is a dual-affinity nitrate transporter. The Km for nitrate was 3.6 mM and 201.7 mM for low-affinity and high-affinity, respectively. However, NPF6.4 showed no dipeptide uptake activity in the yeast complementation assay. In addition, NPF6.4 also displayed the polyamine transport activity by using yeast complementation assay. This study has shown that besides NPF6.3/CHL1, NPF6.4 is another dual-affinity nitrate transporter in the NPF in Arabidopsis, and NPF may have the ability to mediate the transport of polyamines.