闡述AtNPF8.1/AtPTR1受質專一性的分子特徵

Abstract

Nitrogen (such as nitrate and peptide) are essential for plant growth and development. The uptake and transport of organic N (such as peptides) is important for many physiological responses. In the past, AtPTR1 has been known as a plasma membrane-localized transporter and a member of the Nitrate transporter 1/Peptide transporter Family (NPF). AtPTR1 can transport several di-, tri-peptides, but not nitrate. In our study, we want to understand the difference in substrate specificity between AtPTR1 and other nitrate transporters in NPF. Therefore, we selected multiple sites to study the effect of nitrate and dipeptide transport. At first, we examined whether the localization of mutated AtPTR1 by the protoplast and found that H534L, H534Y, 120-140, and 268-311 has lost the plasma membrane-localized property. In yeast complementation assay, we analyzed the di-peptide uptake ability of mutated AtPTR1. We found Y45I, Y346H, C31A, C31, C318A, C318S, H534K reduced the di-peptide uptake ability, and Y45IY46I, Y45IY46IY346H loss of the di-peptide uptake ability. We also showed that no mutated AtPTR1 proteins can uptake nitrate by using the Xenopus oocyte expression system. In this study, the mutant protein that can affect substrate determination to nitrate haven’t been found. However, we understand some mutations of the specific sites can affect the localization of AtPTR1, and some mutations also can cause the reduction or loss of the di-peptide uptake ability. These findings of the substrate specificity of AtPTR1 can be used as a model to understand and study the functions and properties of other NPF members.