Nitrate transporters: an overview in legumes

Abstract

Main conclusion The nitrate transporters, belonging to NPF and NRT2 families, play critical roles in nitrate signaling, root growth and nodule development in legumes.Nitrate plays an essential role during plant development as nutrient and also as signal molecule, in both cases working via the activity of nitrate transporters. To date, few studies on NRT2 or NPF nitrate transporters in legumes have been reported, and most of those concern Lotus japonicus and Medicago truncatula. A molecular characterization led to the identification of 4 putative LjNRT2 and 37 putative LjNPF gene sequences in L. japonicus. In M. truncatula, the NRT2 family is composed of 3 putative members. Using the new genome annotation of M. truncatula (Mt4.0), we identified, for this review, 97 putative MtNPF sequences, including 32 new sequences relative to previous studies. Functional characterization has been published for only two MtNPF genes, encoding nitrate transporters of M. truncatula. Both transporters have a role in root system development via abscisic acid signaling: MtNPF6.8 acts as a nitrate sensor during the cell elongation of the primary root, while MtNPF1.7 contributes to the cellular organization of the root tip and nodule formation. An in silico expression study of MtNPF genes confirmed that NPF genes are expressed in nodules, as previously shown for L. japonicus, suggesting a role for the corresponding proteins in nitrate transport, or signal perception in nodules. This review summarizes our knowledge of legume nitrate transporters and discusses new roles for these proteins based on recent discoveries.

Genome-Wide Systematic Characterization of the NPF Family Genes and Their Transcriptional Responses to Multiple Nutrient Stresses in Allotetraploid Rapeseed

“…The gene structures of BnaNPF s are highly conserved within the same sub-family ( Figures S1 and S2 , Table S2 ). Similar results have been reported in Arabidopsis [ 8 ], rice [ 5 ], Medicago truncatula [ 34 ], sugarcane [ 36 ], and poplar [ 32 ]. For example, in line with the counterparts in Arabidopsis , most of the NPF genes in B. napus contained three introns and four exons such as NPF2;13 , NPF4;2 , NPF5;3 , NPF5;10 , and NPF8;2 subgroup members.…”

“…They facilitate transport of a wide variety of nitrogenous compounds [ 11 , 44 ]. NPF genes have been identified within many species over the last decades, such as Arabidopsis [ 8 ], poplar [ 32 ], Medicago truncatula [ 34 ], rice [ 5 , 43 ], apple [ 35 ] and sugarcane [ 36 ]. However, the number of NPF family members varies largely among species.…”

“…N shortage in the soil may inhibit the growth of B. napus , and its yield production and quality [ 30 , 31 ]. NPF families have been identified in various plant species, such as poplar [ 32 ], wheat [ 33 ], legumes [ 34 ], apple [ 35 ] and sugarcane [ 36 ]. However, little is known about the NPF family genes in oil crops such as B. napus .…”

Genome-Wide Identification and Analysis of Apple NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER Family (NPF) Genes Reveals MdNPF6.5 Confers High Capacity for Nitrogen Uptake under Low-Nitrogen Conditions

“…The MdNPFs are highly and structurally conserved, based on our comprehensive analyses of amino acid sequence alignments, phylogenetics, and conserved domains ( Figure 1 and Figure 3 and Supplementary Materials, Figure S1 ). Similar results have been reported for Arabidopsis [ 15 ], rice [ 14 ], legume plants such as Medicago [ 49 , 51 ], and poplar [ 48 ]. For example, apple NPF2.11 , NPF5.1 , NPF5.13 , NPF6.3 , and NPF8.1 share the same exon‒intron structures and exon lengths with members found in other species.…”

“…The number of NPF family members varies greatly among species. For example, 51, 53, 68, 80, and 93 genes have been reported for Capsella rubella [ 19 ], Arabidopsis [ 15 ], poplar [ 48 ], Medicago truncatula [ 49 ] and rice [ 19 ], respectively. By comparison, the apple genome contains 139 NPF genes, making this family much more prominent there than in other species [ 19 ].…”