title: Rice nitrate transporter OsNPF2.4 functions in low-affinity acquisition and long-distance transport.
abstract: Plant proteins belonging to the NPF (formerly NRT1/PTR) family are well represented in every genome and function in transporting a wide variety of substrates. In this study, we showed that rice OsNPF2.4 is located in the plasma membrane and is expressed mainly in the epidermis, xylem parenchyma, and phloem companion cells. Functional analysis in oocytes showed that OsNPF2.4 is a pH-dependent, low-affinity NO₃⁻ transporter. Short-term (¹⁵NO₃⁻) influx rate, long-term NO₃⁻ acquisition by root, and upward transfer from root to shoot were decreased by disruption of OsNPF2.4 and increased by OsNPF2.4 overexpression under high NO₃⁻ supply. Moreover, the redistribution of NO₃⁻ in the mutants in comparison with the wild type from the oldest leaf to other organs, particularly to N-starved roots, was dramatically changed. Knockout of OsNPF2.4 decreased rice growth and potassium (K) concentration in xylem sap, root, culm, and sheath, but increased the shoot:root ratio of tissue K under higher NO₃⁻. We conclude that OsNPF2.4 functions in acquisition and long-distance transport of NO₃⁻ , and that altering its expression has an indirect effect on K recycling between the root and shoot.
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement and MOA Key Laboratory of Plant Nutrition and Fertilization in Lower-Middle Reaches of the Yangtze River, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Xiudong
authors.initials: X
authors.lastname: Xia
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement and MOA Key Laboratory of Plant Nutrition and Fertilization in Lower-Middle Reaches of the Yangtze River, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Fan
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement and MOA Key Laboratory of Plant Nutrition and Fertilization in Lower-Middle Reaches of the Yangtze River, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Jia
authors.initials: J
authors.lastname: Wei
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement and MOA Key Laboratory of Plant Nutrition and Fertilization in Lower-Middle Reaches of the Yangtze River, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Huimin
authors.initials: H
authors.lastname: Feng
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement and MOA Key Laboratory of Plant Nutrition and Fertilization in Lower-Middle Reaches of the Yangtze River, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Hongye
authors.initials: H
authors.lastname: Qu
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement and MOA Key Laboratory of Plant Nutrition and Fertilization in Lower-Middle Reaches of the Yangtze River, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Dan
authors.initials: D
authors.lastname: Xie
authors.affiliation: Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Miller
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement and MOA Key Laboratory of Plant Nutrition and Fertilization in Lower-Middle Reaches of the Yangtze River, Nanjing Agricultural University, Nanjing 210095, PR China ghxu@njau.edu.cn.
authors.forename: Guohua
authors.initials: G
authors.lastname: Xu
mesh_terms: D027321:Anion Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D000091285:Nitrate Transporters; D009566:Nitrates / Q000378:metabolism*; D012275:Oryza / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D011188:Potassium / Q000378:metabolism
chemical_list: D027321:Anion Transport Proteins; D000091285:Nitrate Transporters; D009566:Nitrates; D011188:Potassium
keywords: Growth reduction; low-affinity nitrate transporter; mutant; overexpression; potassium recycling; rice.