Ectopic expression of a grape nitrate transporter VvNPF6.5 improves nitrate content and nitrogen use efficiency in Arabidopsis

Abstract

Abstract Background Nitrate plays an important role in grapevines vegetative and reproductive development. However, how grapevines uptake, translocate and utilize nitrate and the molecular mechanism still remains to be investigated. Results In this study, we report the functional characterization of VvNPF6.5, a member of nitrate transporter 1/peptide transporter family (NRT1/PTR/NPF) in Vitis vinifera. Subcellular localization in Arabidopsis protoplasts indicated that VvNPF6.5 is plasma membrane localized. Quantitative RT-PCR analysis indicated that VvNPF6.5 is expressed predominantly in roots and stems and its expression is rapidly induced by nitrate. Functional characterization using cRNA-injected Xenopus laevis oocytes showed that VvNPF6.5 uptake nitrate in a pH dependent way and function as a dual-affinity nitrate transporter involved in both high- and low-affinity nitrate uptake. Further ectopic expression of VvNPF6.5 in Arabidopsis resulted in more 15NO3 − accumulation in shoots and roots and significantly improved nitrogen use efficiency (NUE). Moreover, VvNPF6.5 might participate in the nitrate signaling by positively regulating the expression of primary nitrate response genes. Conclusion Our results suggested that VvNPF6.5 encodes a pH-dependent, dual-affinity nitrate transporter. VvNPF6.5 regulates nitrate uptake and allocation in grapevines and is involved in primary nitrate response.

Keywords

• Nitrate
• Transporter
• Grape
• Nitrogen use efficiency
• Nitrate signaling