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The plant hormone gibberellin (GA) regulates multiple developmental processes. It accumulates in the root elongating endodermis, but how it moves into this cell file and the significance of this accumulation are unclear. Here we identify three NITRATE TRANSPORTER1/PEPTIDE TRANSPORTER (NPF) transporters required for GA and abscisic acid (ABA) translocation. We demonstrate that NPF2.14 is a subcellular GA/ABA transporter, presumably the first to be identified in plants, facilitating GA and ABA accumulation in the root endodermis to regulate suberization. Further, NPF2.12 and NPF2.13, closely related proteins, are plasma membrane-localized GA and ABA importers that facilitate shoot-to-root GA12 translocation, regulating endodermal hormone accumulation. This work reveals that GA is required for root suberization and that GA and ABA can act non-antagonistically. We demonstrate how the clade of transporters mediates hormone flow with cell-file-specific vacuolar storage at the phloem unloading zone, and slow release of hormone to induce suberin formation in the maturation zone.

The coding sequence of EhNPF6.3, a homolog of the Arabidopsis thaliana dual-affinity nitrate transporter gene AtNPF6.3 (NRT1.1/CHL1), was cloned from the halophyte Eutrema halophilum (C.A.Mey.) O.E.Schulz /Thellungiella halophila. Expression of EhNPF6.3 in cells of a yeast Ogataea (Hansenula) polymorpha mutant strain for YNT1, the gene of the only nitrate transporter in this organism, restored nitrate uptake by the mutant cells and their ability to growth in selective media containing nitrate as the sole nitrogen source. Examination of nitrate ion uptake from the culture media by cells of O. polymorpha (Morais & M.H. Maia) Y. Yamada, K. Maeda and Mikata strains of wild-type, the Δynt1 knockout mutant, and the knockout mutant expressing EhNPF6.3, using a nitrate-selective electrode, showed that the rate of nitrate uptake by the halophyte transporter, EhNPF6.3, was comparable to that by the endogenous yeast nitrate transporter, YNT1. The results obtained indicate that the protein cloned from the halophyte E. halophilum, EhNPF6.3, is an ortholog of the dual-affinity nitrate transporter and, most likely, plays an important role in nitrate uptake and nitrate distribution among organs and tissues in E. halophilum plants. [ABSTRACT FROM AUTHOR]

Nitrate uptake by plants primarily relies on two gene families: Nitrate transporter 1/peptide transporter (NPF) and Nitrate transporter 2 (NRT2). Here, we extensively characterized the NPF and NRT2 families in the durum wheat genome, revealing 211 NPF and 20 NRT2 genes. The two families share many Cis Regulatory Elements (CREs) and Transcription Factor binding sites, highlighting a partially overlapping regulatory system and suggesting a coordinated response for nitrate transport and utilization. Analyzing RNA-seq data from 9 tissues and 20 cultivars, we explored expression profiles and co-expression relationships of both gene families. We observed a strong correlation between nucleotide variation and gene expression within the NRT2 gene family, implicating a shared selection mechanism operating on both coding and regulatory regions. Furthermore, NPF genes showed highly tissue-specific expression profiles, while NRT2s were mainly divided in two co-expression modules, one expressed in roots (NAR2/NRT3 dependent) and the other induced in anthers and/ovaries during maturation. Our evidences confirmed that the majority of these genes were retained after small-scale duplication events, suggesting a neo- or sub-functionalization of many NPFs and NRT2s. Altogether, these findings indicate that the expansion of these gene families in durum wheat could provide valuable genetic variability useful to identify NUE-related and candidate genes for future breeding programs in the context of low-impact and sustainable agriculture. [ABSTRACT FROM AUTHOR]

Plants uptake and assimilate nitrogen from the soil in the form of nitrate, ammonium ions, and available amino acids from organic sources. Plant nitrate and ammonium transporters are responsible for nitrate and ammonium translocation from the soil into the roots. The unique structure of these transporters determines the specificity of each transporter, and structural analyses reveal the mechanisms by which these transporters function. Following absorption, the nitrogen metabolism pathway incorporates the nitrogen into organic compounds via glutamine synthetase and glutamate synthase that convert ammonium ions into glutamine and glutamate. Different isoforms of glutamine synthetase and glutamate synthase exist, enabling plants to fine-tune nitrogen metabolism based on environmental cues. Under stressful conditions, nitric oxide has been found to enhance plant survival under drought stress. Furthermore, the interaction between salinity stress and nitrogen availability in plants has been studied, with nitric oxide identified as a potential mediator of responses to salt stress. Conversely, excessive use of nitrate fertilizers can lead to health and environmental issues. Therefore, alternative strategies, such as establishing nitrogen fixation in plants through diazotrophic microbiota, have been explored to reduce reliance on synthetic fertilizers. Ultimately, genomics can identify new genes related to nitrogen fixation, which could be harnessed to improve plant productivity. [ABSTRACT FROM AUTHOR]

When plants are exposed to environmental stress, their growth is inhibited. Under such conditions, controlled inhibition of growth is beneficial for plant survival. Jasmonic acid (JA) is a well-known phytohormone that limits plant growth, which has been confirmed in several species. However, its role in cucumber seedlings has not yet been comprehensively investigated. For this reason, we aimed to determine the involvement of JA in the regulation of proteins crucial for growth including plasma membrane proton pump (PM H+-ATPase), PM nitrate transporters, and nitrate reductase (NR). Treatment of cucumber seedlings with JA not only limited their growth but also increased the H2O2 content in their roots. The main sources of ROS generated for signalling purposes are PM NADPH oxidase (RBOH) and superoxide dismutase (SOD). Exposure of seedlings to JA induced the expression of some CsRBOH and SOD encoding genes, suggesting that ROS signalling can be activated by JA. As a consequence of JA exposure, the activity of all analysed proteins was inhibited and the expression of their genes was modified. The results indicate that reduction of PM H+-ATPase activity and the related decrease in nitrate uptake and assimilation are responsible for the root growth retardation of JA-treated plants. [ABSTRACT FROM AUTHOR]

Nitrate uptake by plants primarily relies on two gene families: Nitrate transporter 1/peptide transporter (NPF) and Nitrate transporter 2 (NRT2). Here, we extensively characterized the NPF and NRT2 families in the durum wheat genome, revealing 211 NPF and 20 NRT2 genes. The two families share many Cis Regulatory Elements (CREs) and Transcription Factor binding sites, highlighting a partially overlapping regulatory system and suggesting a coordinated response for nitrate transport and utilization. Analyzing RNA-seq data from 9 tissues and 20 cultivars, we explored expression profiles and co-expression relationships of both gene families. We observed a strong correlation between nucleotide variation and gene expression within the NRT2 gene family, implicating a shared selection mechanism operating on both coding and regulatory regions. Furthermore, NPF genes showed highly tissue-specific expression profiles, while NRT2s were mainly divided in two co-expression modules, one expressed in roots (NAR2/NRT3 dependent) and the other induced in anthers and/ovaries during maturation. Our evidences confirmed that the majority of these genes were retained after small-scale duplication events, suggesting a neo- or sub-functionalization of many NPFs and NRT2s. Altogether, these findings indicate that the expansion of these gene families in durum wheat could provide valuable genetic variability useful to identify NUE-related and candidate genes for future breeding programs in the context of low-impact and sustainable agriculture.

Nitrate is the primary form of nitrogen uptake in plants, mainly transported by nitrate transporters (NRTs), including NPF (NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER FAMILY), NRT2 and NRT3. In this study, we identified a total of 78 NPF, seven NRT2, and two NRT3 genes in maize. Phylogenetic analysis divided the NPF family into eight subgroups (NPF1-NPF8), consistent with the results in Arabidopsis thaliana and rice. The NRT2 family appears to have evolved more conservatively than the NPF family, as NRT2 genes contain fewer introns. The promoters of all NRTs are rich in cis-acting elements responding to biotic and abiotic stresses. The expression of NRTs varies in different tissues and developmental stages, with some NRTs only expressed in specific tissues or developmental stages. RNA-seq analysis using Xu178 revealed differential expression of NRTs in response to nitrogen starvation and nitrate resupply. Moreover, the expression patterns of six key NRTs genes (NPF6.6, NPF6.8, NRT2.1, NRT2.5 and NRT3.1A/B) varied in response to alterations in nitrogen levels across distinct maize inbred lines with different nitrogen uptake rates. This work enhances our understanding of the structure and expression of NRTs genes, and their roles in nitrate response, paving the way for improving maize nitrogen efficiency through molecular breeding. [ABSTRACT FROM AUTHOR]

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Nitrate transporters (NRTs) are crucial for the uptake, use, and storage of nitrogen by plants. In this study, 42 members of the GhNRT2 (Nitrate Transporter 2 family) were found in the four different cotton species. The conserved domains, phylogenetic relationships, physicochemical properties, subcellular localization, conserved motifs, gene structure, cis-acting elements, and promoter region expression patterns of these 42 members were analyzed. The findings confirmed that members of the NRT2 family behaved typically, and subcellular localization tests confirmed that they were hydrophobic proteins that were mostly located on the cytoplasmic membrane. TheNRT2 family of geneswithA.thaliana and rice underwent phylogenetic analysis, and the results revealed that GhNRT2 could be divided into three groups. The same taxa also shared similar gene structure and motif distribution. The composition of cis-acting elements suggests that most of the expression of GhNRT2 may be related to plant hormones, abiotic stress, and photoreactions. The GhNRT2 gene was highly expressed, mainly in roots. Drought, salt, and extreme temperature stress showed that GhNRT2 gene expressionwas significantly up-regulated or down-regulated, indicating that itmay be involved in the stress response of cotton. In general, the genes of the NRT2 family of cotton were comprehensively analyzed, and their potential nitrogen uptake and utilization functions in cotton were preliminarily predicted. Additionally, we provide an experimental basis for the adverse stress conditions in which they may function. [ABSTRACT FROM AUTHOR]

Development of high yield rice varieties is critical to ensuring global food security. However, the emission of greenhouse gases (GHG) such as Methane (CH4) and Nitrous oxide (N2O) from paddy fields threatens environmental sustainability. In this study, we selected overexpressed high-affinity nitrate transporters (NRT2.3 along with their partner protein NAR2.1) cultivars, which are effective nitrogen use efficient transgenic lines pOsNAR2.1: OsNAR2.1 (Ox2) and p35S:OsNRT2.3b (O8). We used high (270 kg N/ha) and low (90 kg N/ha) nitrogen (N) fertilizers in paddy fields to evaluate morphophysiological traits, including GHG emission. We found that Ox2 and O8 reduced CH4 emissions by 40% and 60%, respectively, compared to their wild type (WT). During growth stages, there was no consistent N2O discharge pattern between WT and transgenics (Ox2, O8) in low and high N application. However, total cumulative N2O in a cropping season reduced in O8 and increased in Ox2 cultivars, compared to WT. Root aerenchyma formation reduced by 30-60% in transgenic lines. Methanogens like mcrA in low and high N were also reduced by up to 50% from rhizosphere of Ox2 and O8. However, the nitrifying bacterial population such as nosZ reduced in both transgenics significantly, but nirK and nirS did not show a consistent variation. The high yield of transgenic rice with limited aerenchyma mitigates the discharge of CH4 and N2O by reducing root exudates that provide substrates for GHG. Our results improve understanding for breeders to serve the purpose of sustainable development. [ABSTRACT FROM AUTHOR]

Nitrate (NO3-) transporters have been identified as the primary targets involved in plant nitrogen (N) uptake, transport, assimilation, and remobilization, all of which are key determinants of nitrogen use efficiency (NUE). However, less attention has been directed toward the influence of plant nutrients and environmental cues on the expression and activities of NO3-transporters. To better understand how these transporters function in improving plant NUE, this review critically examined the roles of NO3-transporters in N uptake, transport, and distribution processes. It also described their influence on crop productivity and NUE, especially when coexpressed with other transcription factors, and discussed these transporters' functional roles in helping plants cope with adverse environmental conditions. We equally established the possible impacts of NO3-transporters on the uptake and utilization efficiency of other plant nutrients while suggesting possible strategic approaches to improving NUE in plants. Understanding the specificity of these determinants is crucial to achieving better N utilization efficiency in crops within a given environment. [ABSTRACT FROM AUTHOR]

Plants uptake and assimilate nitrogen from the soil in the form of nitrate, ammonium ions, and available amino acids from organic sources. Plant nitrate and ammonium transporters are responsible for nitrate and ammonium translocation from the soil into the roots. The unique structure of these transporters determines the specificity of each transporter, and structural analyses reveal the mechanisms by which these transporters function. Following absorption, the nitrogen metabolism pathway incorporates the nitrogen into organic compounds via glutamine synthetase and glutamate synthase that convert ammonium ions into glutamine and glutamate. Different isoforms of glutamine synthetase and glutamate synthase exist, enabling plants to fine-tune nitrogen metabolism based on environmental cues. Under stressful conditions, nitric oxide has been found to enhance plant survival under drought stress. Furthermore, the interaction between salinity stress and nitrogen availability in plants has been studied, with nitric oxide identified as a potential mediator of responses to salt stress. Conversely, excessive use of nitrate fertilizers can lead to health and environmental issues. Therefore, alternative strategies, such as establishing nitrogen fixation in plants through diazotrophic microbiota, have been explored to reduce reliance on synthetic fertilizers. Ultimately, genomics can identify new genes related to nitrogen fixation, which could be harnessed to improve plant productivity.

When plants are exposed to environmental stress, their growth is inhibited. Under such conditions, controlled inhibition of growth is beneficial for plant survival. Jasmonic acid (JA) is a well-known phytohormone that limits plant growth, which has been confirmed in several species. However, its role in cucumber seedlings has not yet been comprehensively investigated. For this reason, we aimed to determine the involvement of JA in the regulation of proteins crucial for growth including plasma membrane proton pump (PM H+-ATPase), PM nitrate transporters, and nitrate reductase (NR). Treatment of cucumber seedlings with JA not only limited their growth but also increased the H2O2 content in their roots. The main sources of ROS generated for signalling purposes are PM NADPH oxidase (RBOH) and superoxide dismutase (SOD). Exposure of seedlings to JA induced the expression of some CsRBOH and SOD encoding genes, suggesting that ROS signalling can be activated by JA. As a consequence of JA exposure, the activity of all analysed proteins was inhibited and the expression of their genes was modified. The results indicate that reduction of PM H+-ATPase activity and the related decrease in nitrate uptake and assimilation are responsible for the root growth retardation of JA-treated plants.

Development of high yield rice varieties is critical to ensuring global food security. However, the emission of greenhouse gases (GHG) such as Methane (CH4) and Nitrous oxide (N2O) from paddy fields threatens environmental sustainability. In this study, we selected overexpressed high-affinity nitrate transporters (NRT2.3 along with their partner protein NAR2.1) cultivars, which are effective nitrogen use efficient transgenic lines pOsNAR2.1: OsNAR2.1 (Ox2) and p35S:OsNRT2.3b (O8). We used high (270 kg N/ha) and low (90 kg N/ha) nitrogen (N) fertilizers in paddy fields to evaluate morphophysiological traits, including GHG emission. We found that Ox2 and O8 reduced CH4 emissions by 40% and 60%, respectively, compared to their wild type (WT). During growth stages, there was no consistent N2O discharge pattern between WT and transgenics (Ox2, O8) in low and high N application. However, total cumulative N2O in a cropping season reduced in O8 and increased in Ox2 cultivars, compared to WT. Root aerenchyma formation reduced by 30-60% in transgenic lines. Methanogens like mcrA in low and high N were also reduced by up to 50% from rhizosphere of Ox2 and O8. However, the nitrifying bacterial population such as nosZ reduced in both transgenics significantly, but nirK and nirS did not show a consistent variation. The high yield of transgenic rice with limited aerenchyma mitigates the discharge of CH4 and N2O by reducing root exudates that provide substrates for GHG. Our results improve understanding for breeders to serve the purpose of sustainable development.

Nitrate (NO3-) transporters have been identified as the primary targets involved in plant nitrogen (N) uptake, transport, assimilation, and remobilization, all of which are key determinants of nitrogen use efficiency (NUE). However, less attention has been directed toward the influence of plant nutrients and environmental cues on the expression and activities of NO3- transporters. To better understand how these transporters function in improving plant NUE, this review critically examined the roles of NO3- transporters in N uptake, transport, and distribution processes. It also described their influence on crop productivity and NUE, especially when co-expressed with other transcription factors, and discussed these transporters’ functional roles in helping plants cope with adverse environmental conditions. We equally established the possible impacts of NO3- transporters on the uptake and utilization efficiency of other plant nutrients while suggesting possible strategic approaches to improving NUE in plants. Understanding the specificity of these determinants is crucial to achieving better N utilization efficiency in crops within a given environment.

Key message: Nitrate uptake in sugarcane roots is regulated at the transcriptional and posttranscriptional levels based on the physiological status of the plant and is likely a determinant mechanism for discrimination against nitrate. Sugarcane (Saccharum spp.) is one of the most suitable energy crops for biofuel feedstock, but the reduced recovery of nitrogen (N) fertilizer by sugarcane roots increases the crop carbon footprint. The low nitrogen use efficiency (NUE) of sugarcane has been associated with the significantly low nitrate uptake, which limits the utilization of the large amount of nitrate available in agricultural soils. To understand the regulation of nitrate uptake in sugarcane roots, we identified the major canonical nitrate transporter genes (NRTs—NITRATE TRANSPORTERS) and then determined their expression profiles in roots under contrasting N conditions. Correlation of gene expression with 15N-nitrate uptake revealed that under N deprivation or inorganic N (ammonium or nitrate) supply in N-sufficient roots, the regulation of ScNRT2.1 and ScNRT3.1 expression is the predominant mechanism for the modulation of the activity of the nitrate high-affinity transport system. Conversely, in N-deficient roots, the induction of ScNRT2.1 and ScNRT3.1 transcription is not correlated with the marked repression of nitrate uptake in response to nitrate resupply or high N provision, which suggested the existence of a posttranscriptional regulatory mechanism. Our findings suggested that high-affinity nitrate uptake is regulated at the transcriptional and presumably at the posttranscriptional levels based on the physiological N status and that the regulation of NRT2.1 and NRT3.1 activity is likely a determinant mechanism for the discrimination against nitrate uptake observed in sugarcane roots, which contributes to the low NUE in this crop species. [ABSTRACT FROM AUTHOR]

Plant root development depends on signaling pathways responding to external and internal signals. In this study we demonstrate the involvement of the Lotus japonicus LjNPF4.6 gene in the ABA and nitrate root responding pathways. LjNPF4.6 expression in roots is induced by external application of both nitrate and ABA. LjNPF4.6 promoter activity is spatially localized in epidermal cell layer and vascular bundle structures with the latter pattern being controlled by externally applied ABA. LjNPF4.6 cRNA injection achieves both nitrate and ABA uptake in Xenopus laevis oocytes and the analyses of L. japonicus knock-out insertion mutants confirmed the role played by LjNPF4.6 in root nitrate uptake. The phenotypic characterization of the Ljnpf4.6 plants indicates the role played by LjNPF4.6 in the root program development in response to exogenously applied nitrate and ABA. Based on the presented data, the mode of action of this transporter is discussed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Masson SAS.)

The nitrate transporter (NRT) and ammonium transporter (AMT) are crucial transmembrane proteins involved in the absorption, transport, and distribution of inorganic nitrogen in wheat. Obtaining NRT/AMT and preparing corresponding antibodies are conducive to probing into their tissue localization and comprehending the nitrogen utilization process in wheat. In this study, four genes ( TaNPF4 . 5 , TaNPF8 . 3 , TaNRT3 . 1 , TaAMT1 . 2 ) with high expression levels were chosen and cloned from 405 genes of the TaNRT / TaNPF family and 23 genes of the TaAMT family identified previously. The transmembrane domains of the four transporters were predicted by HMMER to determine the putative expression segments, followed by prokaryotic expression and purification. Under the induction with 1 mmol/L IPTG at 37 ℃, the non-transmembrane segments of TaNPF4.5, TaNPF8.3, and TaNRT3.1 reached the highest expression levels (as inclusion bodies) after 4 h, while TaAMT1.2 was expressed at the highest level (as a soluble protein) after 3 h. TaNPF4.5, TaNPF8.3, and TaNRT3.1 were purified by a pH gradient. The purity of TaNPF4.5 and TaNPF8.3 reached about 87% and 85% at pH 2.0 and pH 3.0, respectively, both of which were suitable for antibody preparation. However, the purity of TaNRT3.1 did not reach 85%. TaAMT1.2 was purified by an imidazole gradient, reaching the purity of about 95% at 20 mmol/L imidazole, and the antibody was prepared successfully. The expression, purification, and antibody preparation of TaAMT1.2 not only provides insights into the expression, purification, and antibody preparation of membrane proteins including TaNPF4.5 and TaNPF8.3 but also lays a foundation for studying the expression and localization of membrane proteins in wheat.

Nitric oxide (NO) and S-nitrosothiol (SNO) are signal molecules and the products of nitrogen metabolism. Nitrate (NO 3 ) is the main nitrogen source, and nitrate transporters (NRTs) are responsible for NO - ) is the main nitrogen source, and nitrate transporters (NRTs) are responsible for NO 3 - absorption or transport. However, the interactive effect between NO 3 - /NRT and NO/SNO in tree plants remains ambiguous. In the present study, 25 mmol L -1 NO 3 - and 1 mmol L -1 NO donor sodium nitroprusside (SNP) treatment that was conducted for 24 h enhanced NO/SNO and NO 3 - metabolism, whereas 2.5 mmol L -1 NO 3 - and 80 μmol L -1 N6022 (a compound that increases SNO content) treatment reduced them in seedling leaves of Fraxinus mandshurica and Betula platyphylla. Among the nine NRT family members examined, the gene expression level of NRT2.1 had a greater response to NO/SNO and NO 3 - treatment in the seedling leaves of F. mandshurica and B. platyphylla. Meanwhile, FmNRT2.1 mediated NO and SNO production in seedling leaves of F. mandshurica using Agrobacterium-mediated transient transformation. These findings shed light on the reciprocal regulation between NO 3 - and NO/SNO in seedlings of F. mandshurica and B. platyphylla, and NRT2.1 may act as a key regulatory hub., Competing Interests: Declaration of competing interest We would like to submit the enclosed manuscript entitled “Crosstalk between NO(3)(−)/NTR2.1 and NO/SNO in seedings of Fraxinus mandshurica and Betula platyphylla” which we wish to be considered for publication in plant physiology and biochemistry. The work described has not been submitted elsewhere for publication, in whole or in part. If accepted, our paper will not be published elsewhere in the same form, in English or in any other language, including electronically without the written consent of the copyright-holder., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

In sweet potato, rational nitrogen (N) assimilation and distribution are conducive to inhibiting vine overgrowth. Nitrate (NO 3 - ) is the main N form absorbed by roots, and cultivar is an important factor affecting N utilization. Herein, a hydroponic experiment was conducted that included four NO 3 - concentrations of 0 (N0), 4 (N1), 8 (N2) and 16 (N3) mmol L -1 with two cultivars of Jishu26 (J26, N-sensitive) and Xushu32 (X32, N-tolerant). For J26, with increasing NO 3 - concentrations, the root length and root surface area significantly decreased. However, no significant differences were observed in these parameters for X32. Higher NO 3 - concentrations upregulated the expression levels of the genes that encode nitrate reductase (NR2), nitrite reductase (NiR2) and nitrate transporter (NRT1.1) in roots for both cultivars. The trends in the activities of NR and NiR were subject to regulation of NR2 and NiR2 transcription, respectively. For both cultivars, N2 increased the N accumulated in leaves, growth points and roots. For J26, N3 further increased the N accumulation in these organs. Under higher NO 3 - nutrition, compared with X32, J26 exhibited higher expression levels of the NiR2, NR2 and NRT1.1 genes, a higher influx NO 3 - rate in roots, and higher activities of NR and NiR in leaves and roots. Conclusively, the regulated effects of NO 3 - supplies on root growth and NO 3 - utilization were more significant for J26. Under high NO 3 - conditions, J26 exhibited higher capacities of NO 3 - absorption and distributed more N in leaves and in growth points, which may contribute to higher growth potential in shoots and more easily cause vine overgrowth., (© 2024. The Author(s).)

Nitrate is the primary form of nitrogen uptake in plants, mainly transported by nitrate transporters (NRTs), including NPF (NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER FAMILY), NRT2 and NRT3. In this study, we identified a total of 78 NPF, seven NRT2, and two NRT3 genes in maize. Phylogenetic analysis divided the NPF family into eight subgroups (NPF1-NPF8), consistent with the results in Arabidopsis thaliana and rice. The NRT2 family appears to have evolved more conservatively than the NPF family, as NRT2 genes contain fewer introns. The promoters of all NRTs are rich in cis-acting elements responding to biotic and abiotic stresses. The expression of NRTs varies in different tissues and developmental stages, with some NRTs only expressed in specific tissues or developmental stages. RNA-seq analysis using Xu178 revealed differential expression of NRTs in response to nitrogen starvation and nitrate resupply. Moreover, the expression patterns of six key NRTs genes (NPF6.6, NPF6.8, NRT2.1, NRT2.5 and NRT3.1A/B) varied in response to alterations in nitrogen levels across distinct maize inbred lines with different nitrogen uptake rates. This work enhances our understanding of the structure and expression of NRTs genes, and their roles in nitrate response, paving the way for improving maize nitrogen efficiency through molecular breeding.

Multiple nitrate transporter (NRT) genes exist in the genome of bread wheat, and it is of great importance to identify the elite NRT genes for N-efficient wheat cultivar breeding. A candidate gene association study (CGAS) of six N use efficiency (NUE) related traits (grain N concentration (GNC), straw N concentration (SNC), grain yield (GY), grain N accumulation (GNA), shoot total N accumulation (STN) and N harvest index (NHI)) was performed based on SNPs in 46 NRT2 genes using a panel composed of 286 wheat cultivars. CGAS identified TaNRT2.1-6B as an elite NRT gene that is significantly associated with four (NHI, SNC, GNA and GY) of the six NUE-related traits simultaneously. TaNRT2.1-6B is located on the plasma membrane and acts as a dual-affinity NRT. The overexpression of TaNRT2.1-6B increased the N influx and root growth of wheat, whereas gene silence lines resulted in the opposite effects. The overexpression of TaNRT2.1-6B also improved GY and N accumulation of wheat under either limited or sufficient N conditions. The data provide the TaNRT2.1-6B gene and the two associated SNP markers as promising powerful tools for breeding wheat cultivars with high N uptake ability and NUE. [ABSTRACT FROM AUTHOR]

Plant growth-promoting fungi are integral components of the root microbiome that help the host resist biotic and abiotic stress while improving nutrient acquisition. Trichoderma atroviride is a common inhabitant of the rhizosphere, which establishes a perdurable symbiosis with plants through the emission of volatiles, diffusible compounds, and robust colonization. Currently, little is known on how the environment influences the Trichoderma–plant interaction. In this report, we assessed plant growth and root architectural reconfiguration of Arabidopsis seedlings grown in physical contact with T. atroviride under contrasting nitrate and ammonium availability. The shoot and root biomass accumulation and lateral root formation triggered by the fungus required high nitrogen supplements and involved nitrate reduction via AtNIA1 and NIA2. Ammonium supplementation did not restore biomass production boosted by T. atroviride in nia1nia2 double mutant, but instead fungal inoculation increased nitric oxide accumulation in Arabidopsis primary root tips depending upon nitrate supplements. N deprived seedlings were largely resistant to the effects of nitric oxide donor SNP triggering lateral root formation. T. atroviride enhanced expression of CHL1:GUS in root tips, particularly under high N supplements and required an intact CHL1 nitrate transporter to promote lateral root formation in Arabidopsis seedlings. These data imply that the developmental programs strengthened by Trichoderma and the underlying growth promotion in plants are dependent upon adequate nitrate nutrition and may involve nitric oxide as a second messenger. [ABSTRACT FROM AUTHOR]

Nitrate is an important nutrient and a key signalling molecule for plant development. A number of transcription factors involved in the response to nitrate and their regulatory mechanisms have been identified. However, little is known about the transcription factors involved in nitrate sensing and their regulatory mechanisms among crop plants. In this study, we identified functions of a nitrate-responsive miR444:MADS-box transcription factor OsMADS27 module and its downstream targets mediating rice root growth and stress responses. Transgenic rice plants expressing miR444 target mimic improved rice root growth. Although miR444 has the potential to target multiple genes, we identified OsMADS27 as the major miR444 target that regulates the expression of nitrate transporters, as well as several key genes including expansins, and those associated with auxin signalling, to promote root growth. In agreement with this, overexpression of miRNA-resistant OsMADS27 improved root development and tolerance to abiotic stresses, while its silencing suppressed root growth. OsMADS27 mediated robust stress tolerance in plants through its ability to bind to the promoters of specific stress regulators, as observed in ChIP-seq analysis. Our results provide evidence of a nitrate-dependent miR444-OsMADS27 signalling cascade involved in the regulation of rice root growth, as well as its surprising role in stress responses. [ABSTRACT FROM AUTHOR]

Rice has a large number of nitrate or peptide transporter family (NPF) genes, but the effects of most members on rice growth and development are unknown. We report that OsNPF5.16, a nitrate transporter gene with natural variation in its promoter sequence, is essential for rice growth and yield. The promoter sequence showed various differences between indica and japonica cultivars, and higher expression of OsNPF5.16 was found in indica cultivars with higher plant weight and more tillers than japonica cultivars. OsNPF5.16 was highly expressed in roots, tiller basal parts, and leaf sheaths, and its protein was localized on the plasma membrane. In cRNA-injected Xenopus laevis oocytes, OsNPF5.16 transport of nitrate at high nitrate concentration depended on pH. Overexpression of OsNPF5.16 increased nitrate content and total nitrogen content in leaf sheath as well as biomass and tiller bud length in rice. Elevated expression of OsNPF5.16 increased rice tiller number and grain yield by regulating cytokinin levels. Inhibition of OsNPF5.16 expression showed the opposite effects. Regulating OsNPF5.16 expression has potential for improving rice grain yield. [ABSTRACT FROM AUTHOR]

To investigate the positive feed-forward regulatory mechanism of nitrate uptake by rice, its responses to various light and carbohydrates were compared. In order to measure nitrate uptake in real time, the non-invasive method was used. The results showed that net nitrate uptake increased in the light and decreased in the dark, and finally reached a steady state after about 5 h. Based on it, carbohydrates effects could be investigated without considering light effects. After sucrose addition for 2 h, net nitrate uptake increased by about 80% without a lag, while glucose, fructose and raffinose had a slight effect with a lag and other sugars had no effect. It provided an evidence that sucrose was a positive feed-forward signal molecule of nitrate uptake by rice roots. To further analyze the effect of sucrose on the expression of high affinity nitrate transporter genes OsNRT2.1, OsNRT2.2, OsNRT2.3a and OsNRT2.3b, qRT-PCR was used to further verify after treated with 10 mM sucrose. The results revealed that these genes expression was immediately up-regulated, which indicated that these genes were post transcriptionally regulated. Further, 15 N exchange dynamics analyzed N transport. It is benefit for increasing nitrate uptake by rice and improving its yield., (© 2024. The Author(s).)

Eucalyptus grandis is an important planted hardwood tree worldwide with fast growth and good wood performance. The nitrate transporter (NRT) gene family is a major core involved in nitrogen (N) absorption and utilization in plants, but the comprehensive characterization of NRT genes in E. grandis remains mostly elusive. In this study, a total of 75 EgNRT genes were identified from the genome of E. grandis that were distributed unevenly across ten chromosomes, except Chr9. A phylogenetic analysis showed that the EgNRT proteins could be divided into three classes, namely NRT1, NRT2 and NRT3, which contained 69, 4 and 2 members, respectively. The cis -regulatory elements in the promoter regions of EgNRT genes were mainly involved in phytohormone and stress response. The transcriptome analysis indicated that the differentially expressed genes of leaf and root in E. grandis under different N supply conditions were mainly involved in the metabolic process and plant hormone signal transduction. In addition, the transcriptome-based and RT-qPCR analysis revealed that the expression of 13 EgNRT genes, especially EgNRT1.3 , EgNRT1.38 , EgNRT1.39 and EgNRT1.52 , was significantly upregulated in the root under low-N-supply treatment, suggesting that those genes might play a critical role in root response to nitrate deficiency. Taken together, these results would provide valuable information for characterizing the roles of EgNRTs and facilitate the clarification of the molecular mechanism underlying EgNRT -mediated N absorption and distribution in E. grandis .

Plant defense responses to the soil-borne fungus Verticillium longisporum causing stem stripe disease on oilseed rape (Brassica napus) are poorly understood. In this study, a population of recombinant inbred lines (RILs) using the Arabidopsis accessions Sei-0 and Can-0 was established. Composite interval mapping, transcriptome data, and T-DNA mutant screening identified the NITRATE/PEPTIDE TRANSPORTER FAMILY 5.12 (AtNPF5.12) gene as being associated with disease susceptibility in Can-0. Co-immunoprecipitation revealed interaction between AtNPF5.12 and the MAJOR LATEX PROTEIN family member AtMLP6, and fluorescence microscopy confirmed this interaction in the plasma membrane and endoplasmic reticulum. CRISPR/Cas9 technology was applied to mutate the NPF5.12 and MLP6 genes in B. napus. Elevated fungal growth in the npf5.12 mlp6 double mutant of both oilseed rape and Arabidopsis demonstrated the importance of these genes in defense against V. longisporum. Colonization of this fungus depends also on available nitrates in the host root. Accordingly, the negative effect of nitrate depletion on fungal growth was less pronounced in Atnpf5.12 plants with impaired nitrate transport. In addition, suberin staining revealed involvement of the NPF5.12 and MLP6 genes in suberin barrier formation. Together, these results demonstrate a dependency on multiple plant factors that leads to successful V. longisporum root infection., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology.)

Nitrate (NO 3 - ) is a significant inorganic nitrogen source in soil, playing a crucial role in influencing crop productivity. As sessile organisms, plants have evolved complex mechanisms for nitrate uptake and response to varying soil levels. Recent advancements have enhanced our understanding of nitrate uptake and signaling pathways. This mini-review offers a comparative analysis of nitrate uptake mechanisms in Arabidopsis and rice. It also examines nitrate signal transduction, highlighting the roles of AtNRT1.1 and AtNLP7 as nitrate receptors and elucidating the OsNRT1.1B-OsSPX4-OsNLP3 cascade. Additionally, it investigates nuclear transcriptional networks that regulate nitrate-responsive genes, controlled by various transcription factors (TFs) crucial for plant development. By integrating these findings, we highlight mechanisms that may help to enhance crop nitrogen utilization., (© 2024 Scandinavian Plant Physiology Society.)

Genome co-editing technology is effective in breeding filamentous fungi for applications in the fermentation industry, achieving site-directed mutagenesis, the status of non-genetically modified organisms (non-GMOs), and wild-type-like growth phenotype. Prior to this study, thiI gene was found as a selectable marker for such genome co-editing in the filamentous fungus Aspergillus oryzae, while it cannot be reused via marker recycling. Therefore, we aimed to identify another marker gene to knock out another target gene via genome co-editing in A. oryzae. In this study, we focused on the membrane transporter gene nrtA (AO090012000623), which promotes uptake of nitrate (NO 3 - ). It is known that, in nrtA knockout strain, chlorate (ClO 3 - ), an analog of nitrate with antifungal activity, cannot be imported into the cytosol, which enables the mutant to grow in the presence of chlorate. Based on this information, knockout of the target gene wA was attempted using both nrtA- and wA-specific single-guide RNAs via genome co-editing with KClO 3 supplementation in A. oryzae laboratory strain RIB40 and industrial strain KBN616. Resultantly, wA knockout mutant was generated, and nrtA was identified as a selectable marker. Moreover, this genome co-editing system using nrtA was compatible with that using thiI, and thus, a double knockout mutant of two target genes wA and yA was constructed in RIB40 while maintaining non-GMO status and wild-type-like growth. As nrtA homologs have been found in several industrial Aspergillus species, genome co-editing using homolog genes as selectable markers is plausible, which would contribute to the widespread breeding of industrial strains of Aspergilli., (Copyright © 2024 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.)

Elucidating the mechanisms regulating nitrogen (N) deficiency responses in plants is of great agricultural importance. Previous studies revealed that decreased expression of NITRATE-INDUCIBLE GARP-TYPE TRANSCRIPTIONAL REPRESSOR1 (NIGT1) transcriptional repressor genes upon N deficiency is involved in N deficiency-inducible gene expression in Arabidopsis thaliana. However, our knowledge of the mechanisms controlling N deficiency-induced changes in gene expression is still limited. Through the identification of Dof1.7 as a direct target of NIGT1 repressors and a novel N deficiency response-related transcriptional activator gene, we here show that NIGT1 and Dof1.7 transcription factors (TFs) differentially regulate N deficiency-inducible expression of three high-affinity nitrate transporter genes, NRT2.1, NRT2.4, and NRT2.5, which are responsible for most of the soil nitrate uptake activity of Arabidopsis plants under N-deficient conditions. Unlike NIGT1 repressors, which directly suppress NRT2.1, NRT2.4, and NRT2.5 under N-sufficient conditions, Dof1.7 directly activated only NRT2.5 but indirectly and moderately activated NRT2.1 and NRT2.4 under N-deficient conditions, probably by indirectly decreasing NIGT1 expression. Thus, Dof1.7 converted passive transcriptional activation into active and potent transcriptional activation, further differentially enhancing the expression of NRT2 genes. These findings clarify the mechanism underlying different expression patterns of NRT2 genes upon N deficiency, suggesting that time-dependent multilayered transcriptional regulation generates complicated expression patterns of N deficiency-inducible genes., (© 2024 The Authors. New Phytologist © 2024 New Phytologist Foundation.)

Global warming will lead to significantly increased temperatures on earth. Plants respond to high ambient temperature with altered developmental and growth programs, termed thermomorphogenesis. Here we show that thermomorphogenesis is conserved in Arabidopsis, soybean, and rice and that it is linked to a decrease in the levels of the two macronutrients nitrogen and phosphorus. We also find that low external levels of these nutrients abolish root growth responses to high ambient temperature. We show that in Arabidopsis, this suppression is due to the function of the transcription factor ELONGATED HYPOCOTYL 5 (HY5) and its transcriptional regulation of the transceptor NITRATE TRANSPORTER 1.1 (NRT1.1). Soybean and Rice homologs of these genes are expressed consistently with a conserved role in regulating temperature responses in a nitrogen and phosphorus level dependent manner. Overall, our data show that root thermomorphogenesis is a conserved feature in species of the two major groups of angiosperms, monocots and dicots, that it leads to a reduction of nutrient levels in the plant, and that it is dependent on environmental nitrogen and phosphorus supply, a regulatory process mediated by the HY5-NRT1.1 module., (© 2024. The Author(s).)

Two genes of nitrate transporters SaNRT2.1 and SaNRT2.5 , putative orthologs of high-affinity nitrate transporter genes AtNRT2.1 and AtNRT2.5 from Arabidopsis thaliana , were cloned from the euhalophyte Suaeda altissima . Phylogenetic bioinformatic analysis demonstrated that the proteins SaNRT2.1 and SaNRT2.5 exhibited higher levels of homology to the corresponding proteins from the plants of family Amaranthaceae; the similarity of amino acid sequences between proteins SaNRT2.1 and SaNRT2.5 was lower (54%). Both SaNRT2.1 and SaNRT2.5 are integral membrane proteins forming 12 transmembrane helices as predicted by topological modeling. An attempt to demonstrate nitrate transporting activity of SaNRT2.1 or SaNRT2.5 by heterologous expression of the genes in the yeast Hansenula ( Ogataea ) polymorpha mutant strain Δ ynt1 lacking the only yeast nitrate transporter was not successful. The expression patterns of SaNRT2.1 and SaNRT2.5 were studied in S. altissima plants that were grown in hydroponics under either low (0.5 mM) or high (15 mM) nitrate and salinity from 0 to 750 mM NaCl. The growth of the plants was strongly inhibited by low nitrogen supply while stimulated by NaCl; it peaked at 250 mM NaCl for high nitrate and at 500 mM NaCl for low nitrate. Under low nitrate supply, nitrate contents in S. altissima roots, leaves and stems were reduced but increased in leaves and stems as salinity in the medium increased. Potassium contents remained stable under salinity treatment from 250 to 750 mM NaCl. Quantitative real-time PCR demonstrated that without salinity, SaNRT2.1 was expressed in all organs, its expression was not influenced by nitrate supply, while SaNRT2.5 was expressed exclusively in roots-its expression rose about 10-fold under low nitrate. Salinity increased expression of both SaNRT2.1 and SaNRT2.5 under low nitrate. SaNRT2.1 peaked in roots at 500 mM NaCl with 15-fold increase; SaNRT2.5 peaked in roots at 500 mM NaCl with 150-fold increase. It is suggested that SaNRT2.5 ensures effective nitrate uptake by roots and functions as an essential high-affinity nitrate transporter to support growth of adult S. altissima plants under nitrogen deficiency.

NRT2.1, the major high affinity nitrate transporter in roots, can be phosphorylated at five different sites within the N- and the C-terminus. Here, we characterized the functional relationship of two N-terminal phosphorylation sites, S21 and S28, in Arabidopsis. Based on a site-specific correlation network, we identified a receptor kinase (HPCAL1, AT5G49770), phosphorylating NRT2.1 at S21 and resulting in active nitrate uptake. HPCAL1 itself was regulated by phosphorylation at S839 and S870 within its kinase domain. In the active state, when S839 was dephosphorylated and S870 was phosphorylated, HPCAL1 was found to interact with the N-terminus of NRT2.1, mainly when S28 was dephosphorylated. Phosphorylation of NRT2.1 at S21 resulted in a reduced interaction of NRT2.1 with its activator NAR2.1, but nitrate transport activity remained. By contrast, phosphorylated NRT2.1 at S28 enhanced the interaction with NAR2.1, but reduced the interaction with HPCAL1. Here we identified HPCAL1 as the kinase affecting this phospho-switch through phosphorylation of NRT2.1 at S21., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Society for Experimental Biology.)

Coordinated carbon and nitrogen metabolism is crucial for bacteria living in the fluctuating environments. Intracellular carbon and nitrogen homeostasis is maintained by a sophisticated network, in which the widespread signaling protein PII acts as a major regulatory hub. In cyanobacteria, PII was proposed to regulate the nitrate uptake by an ABC (ATP-binding cassette)-type nitrate transporter NrtABCD, in which the nucleotide-binding domain of NrtC is fused with a C-terminal regulatory domain (CRD). Here, we solved three cryoelectron microscopy structures of NrtBCD, bound to nitrate, ATP, and PII, respectively. Structural and biochemical analyses enable us to identify the key residues that form a hydrophobic and a hydrophilic cavity along the substrate translocation channel. The core structure of PII, but not the canonical T-loop, binds to NrtC and stabilizes the CRD, making it visible in the complex structure, narrows the substrate translocation channel in NrtB, and ultimately locks NrtBCD at an inhibited inward-facing conformation. Based on these results and previous reports, we propose a putative transport cycle driven by NrtABCD, which is allosterically inhibited by PII in response to the cellular level of 2-oxoglutarate. Our findings provide a distinct regulatory mechanism of ABC transporter via asymmetrically binding to a signaling protein., Competing Interests: Competing interests statement:The authors declare no competing interest.

Nitrogen is the most limiting nutrient for plants, and it is preferentially absorbed in the form of nitrate by roots, which adapt to nitrate fluctuations by remodelling their architecture. Although core mechanisms of the response to nitrate availability are relatively well-known, signalling events controlling root growth and architecture have not all been identified, in particular in Legumes. However, the developmental effect of nitrate in Legumes is critical since external nitrate not only regulates root architecture but also N 2 -fixing nodule development. We have previously shown that in barrel medic (Medicago truncatula), the nitrate transporter MtNPF6.8 is required for nitrate sensitivity in root tip. However, uncertainty remains as to whether nitrogen metabolism itself is involved in the MtNPF6.8-mediated response. Here, we examine the metabolic effects of MtNPF6.8-dependent nitrate signalling using metabolomics and proteomics in WT and mtnpf6.8 root tips in presence or absence of nitrate. We found a reorchestration of metabolism due to the mutation, in favour of the branched chain amino acids/pantothenate metabolic pathway, and lipid catabolism via glyoxylate. That is, the mtnpf6.8 mutation was likely associated with a specific rerouting of acetyl-CoA production (glyoxylic cycle) and utilisation (pantothenate and branched chain amino acid synthesis). In agreement with our previous findings, class III peroxidases were confirmed as the main protein class responsive to nitrate, although in an MtNPF6.8-independent fashion. Our data rather suggest the involvement of other pathways within mtnpf6.8 root tips, such as Ca 2+ signalling or cell wall methylation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Masson SAS. All rights reserved.)

A nitrate transporter gene, named B46NRT2.1 , from salt-tolerant Zea mays L. B46 has been cloned. B46NRT2.1 contained the same domain belonging to the major facilitator superfamily (PLN00028). The results of the phylogenetic tree indicated that B46NRT2.1 exhibits sequence similarity and the closest relationship with those known nitrate transporters of the NRT2 family. Through RT-qPCR, we found that the expression of B46NRT2.1 mainly happens in the root and leaf. Moreover, the treatment with NaCl, Na 2 CO 3 , and NaHCO 3 could significantly increase the expression of B46NRT2.1 . B46NRT2.1 was located in the plasma membrane. Through the study of yeast and plant salt response brought by B46NRT2.1 overexpression, we have preliminary knowledge that the expression of B46NRT2.1 makes yeast and plants respond to salt shock. There are 10 different kinds of cis-acting regulatory elements (CRES) in the promotor sequences of B46NRT2.1 gene using the PlantCARE web server to analyze. It mainly includes hormone response, abscisic acid, salicylic acid, gibberellin, methyl jasmonate, and auxin. The B46NRT2.1 gene's co-expression network showed that it was co-expressed with a number of other genes in several biological pathways, including regulation of NO 3 long-distance transit, modulation of nitrate sensing and metabolism, nitrate assimilation, and transduction of Jasmonic acid-independent wound signal. The results of this work should serve as a good scientific foundation for further research on the functions of the NRT2 gene family in plants (inbred line B46), and this research adds to our understanding of the molecular mechanisms under salt tolerance.

Nitrogen (N) is essential for plant growth and development. Therefore, understanding its utilization is essential for improving crop productivity. However, much remains to be learned about plant N sensing and signaling. Here, rice (Oryza sativa) NUCLEAR FACTOR-YA5 (OsNF-YA5) expression was tightly regulated by N status and induced under N-deficient conditions. Overexpression (OE) of OsNF-YA5 in rice resulted in increased chlorophyll levels and delayed senescence compared to control plants under normal N conditions. Agronomic traits were significantly improved in OE plants and impaired in knockout mutants under N-deficient conditions. Using a dexamethasone-inducible system, we identified the putative targets of OsNF-YA5 that include amino acid, nitrate/peptide transporters, and NITRATE TRANSPORTER 1.1A (OsNRT1.1A), which functions as a key transporter in rice. OsNF-YA5 directly enhanced OsNRT1.1A expression and N uptake rate under N-deficient conditions. Besides, overexpression of OsNF-YA5 also enhanced the expression of GLUTAMINE SYNTHETASE 1/2 (GS1/2) and GLUTAMINE OXOGLUTARATE AMINOTRANSFERASE 1/2 (GOGAT1/2), increasing free amino acid contents under N-deficient conditions. Osa-miR169a expression showed an opposite pattern with OsNF-YA5 depending on N status. Further analysis revealed that osa-miR169a negatively regulates OsNF-YA5 expression and N utilization, demonstrating that an OsNF-YA5/osa-miR169a module tightly regulates rice N utilization for adaptation to N status., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2023. Published by Oxford University Press on behalf of American Society of Plant Biologists.)

High-affinity nitrate transporters (NRT) are key components for nitrogen (N) acquisition and distribution within plants. However, insights on these transporters in wheat are scarce. This study presents a comprehensive analysis of the NRT2 and NRT3 gene families, where the aim is to shed light on their functionality and to evaluate their responses to N availability. A total of 53 NRT2s and 11 NRT3s were identified in the bread wheat genome, and these were grouped into different clades and homoeologous subgroups. The transcriptional dynamics of the identified NRT2 and NRT3 genes, in response to N starvation and nitrate resupply, were examined by RT-qPCR in the roots and shoots of hydroponically grown wheat plants through a time course experiment. Additionally, the spatial expression patterns of these genes were explored within the plant. The NRT2s of clade 1, TaNRT2.1-2.6 , showed a root-specific expression and significant upregulation in response to N starvation, thus emphasizing a role in N acquisition. However, most of the clade 2 NRT2s displayed reduced expression under N-starved conditions. Nitrate resupply after N starvation revealed rapid responsiveness in TaNRT2.1-2.6 , while clade 2 genes exhibited gradual induction, primarily in the roots. TaNRT2.18 was highly expressed in above-ground tissues and exhibited distinct nitrate-related response patterns for roots and shoots. The TaNRT3 gene expression closely paralleled the profiles of TaNRT2.1-2.6 in response to nitrate induction. These findings enhance the understanding of NRT2 and NRT3 involvement in nitrogen uptake and utilization, and they could have practical implications for improving nitrogen use efficiency. The study also recommends a standardized nomenclature for wheat NRT2 genes, thereby addressing prior naming inconsistencies.

NITRATE TRANSPORTER 1 (NRT1)/PEPTIDETRANSPORTER (PTR) family (NPF) plays a significant role in nitrate transport. However, little is known about the NPF genes in sweet cherry. In this study, a total of 60 PaNPF genes in sweet cherry were identified by bioinformatics, which were divided into 8 families. Transcriptomic analysis showed that most PaNPF genes responded to both low and high nitrate conditions, especially PaNPF5.5, which was highly up-regulated under high nitrate condition. Molecular analysis showed that PaNPF5.5 was a transporter localized to the cell membrane. Further functional studies found that PaNPF5.5 overexpression promoted the growth of sweet cherry rootstock Gisela 6 by accelerating the nitrogen absorption process under high nitrate environment. Taken together, we believe that PaNPF5.5 plays an important role in regulating the transport of nitrate at high nitrate conditions, and provides a promising method for improving nitrate absorption efficiency at nitrogen excess environment., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Nitrogen fertilization can promote rice yield but decrease resistance to sheath blight (ShB). In this study, the nitrate transporter 1.1b ( nrt1.1b ) mutant that exhibited less susceptibility to ShB but without compromising yield under NH 4 + fertilization was screened. NRT1.1B's regulation of ShB resistance was independent of the total nitrogen concentration in rice under NH 4 + conditions. In nrt1.1b mutant plants, the NH 4 + application modulated auxin signaling, chlorophyll content, and phosphate signaling to promote ShB resistance. Furthermore, the findings indicated that NRT1.1B negatively regulated ShB resistance by positively modulating the expression of H + -ATPase gene OSA3 and phosphate transport gene PT8 . The mutation of OSA3 and PT8 promoted ShB resistance by increasing the apoplastic pH in rice. Our study identified the ShB resistance mutant nrt1.1b , which maintained normal nitrogen use efficiency without compromising yield.

The kernel serves as the storage organ and harvestable component of maize, and it plays a crucial role in determining crop yield and quality. Understanding the molecular and genetic mechanisms of kernel development is of considerable importance for maize production. In this study, we obtained a mutant, which we designated defective kernel 407 ( dek407 ), through ethyl methanesulfonate mutagenesis. The dek407 mutant exhibited reduced kernel size and kernel weight, as well as delayed grain filling compared with those of the wild type. Positional cloning and an allelism test revealed that Dek407 encodes a nitrate transporter 1/peptide transporter family (NPF) protein and is the allele of miniature 2 ( mn2 ) that was responsible for a poorly filled defective kernel phenotype. A transcriptome analysis of the developing kernels showed that the mutation of Dek407 altered the expression of phytohormone-related genes, especially those genes associated with indole-3-acetic acid synthesis and signaling. Phytohormone measurements and analysis indicated that the endogenous indole-3-acetic acid content was significantly reduced by 66% in the dek407 kernels, which may be the primary cause of the defective phenotype. We further demonstrated that natural variation in Dek407 is associated with kernel weight and kernel size. Therefore, Dek407 is a potential target gene for improvement of maize yield.

Nitrogen (N) is the key essential macronutrient for crop growth and yield. Over-application of inorganic N fertilizer in fields generated serious environmental pollution and had a negative impact to human health. Therefore, improving crop N use efficiency (NUE) is helpful for sustainable agriculture. The biological functions of nitrogen transporters and regulators have been intensively studied in many crop species. However, only a few nitrogen transporters have been identified in tobacco to date. We reported the identification and functional characterization of a nitrate transporter NtNPF2.11 from tobacco (Nicotiana tabacum). qRT-PCR assay revealed that NtNPF2.11 was mainly expressed in leaf and vein. Under middle N (MN, 1.57 kg N/100 m 2 ) and high N (HN, 2.02 kg N/100 m 2 ) conditions, overexpression of NtNPF2.11 in tobacco greatly improved N utilization and biomass. Moreover, under middle N and high N conditions, the expression of genes for nitrate assimilation, such as NtNR1, NtNiR, NtGS and NtGOGAT, were upregulated in NtNPF2.11 overexpression plants. Compared with WT, overexpression of NtNPF2.11 increased potassium (K) accumulation under high N conditions. These results indicated that overexpression of NtNPF2.11 could increase tobacco yield, N and K accumulation under higher N conditions. Overall, these findings improve our understanding the function of NtNPF2.11 and provide useful gene for sustainable agriculture., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Nitrate is a primary nitrogen source for plant growth, and previous studies have indicated a correlation between nitrogen and browning. Nitrate transporters (NRTs) are crucial in nitrate allocation. Here, we utilized a genome-wide approach to identify and analyze the expression pattern of 74 potential GbNRTs under nitrate treatments during calluses browning in Ginkgo, including 68 NITRATE TRANSPORTER 1 (NRT1)/PEPTIDE TRANSPORTER (PTR) (NPF), 4 NRT2 and 2 NRT3. Conserved domains, motifs, phylogeny, and cis-acting elements (CREs) were analyzed to demonstrate the evolutionary conservation and functional diversity of GbNRTs. Our analysis showed that the NPF family was divided into eight branches, with the GbNPF2 and GbNPF6 subfamilies split into three groups. Each GbNRT contained 108-214 CREs of 19-36 types, especially with binding sites of auxin and transcription factors v-myb avian myeloblastosis viral oncogene homolog (MYB) and basic helix-loop-helix (bHLH). The E 1 X 1 X 2 E 2 R motif had significant variations in GbNPFs, indicating changes in the potential dynamic proton transporting ability. The expression profiles of GbNRTs indicated that they may function in regulating nitrate uptake and modulating the signaling of auxin and polyphenols biosynthesis, thereby affecting browning in Ginkgo callus induction. These findings provide a better understanding of the role of NRTs during NO 3 - uptake and utilization in vitro culture, which is crucial to prevent browning and develop an efficient regeneration and suspension production system in Ginkgo., (© 2023. BioMed Central Ltd., part of Springer Nature.)

A reduction in chemical N-based fertillizer was investigated in Citrus plants. As N and water uptake are connected, the relationship between the physiological response to reductions in N was studied in relation to N metabolism and water. We examined the response of new and mature leaves and roots of Citrus macrophylla, grown under controlled conditions, and given different concentrations of N: 16, 8 or 4 mM. Differences in growth and development were determined for biochemical (mineral content, photosynthetic pigments, proteins and nitrate and nitrite reductase activity), physiological (photosynthesis and transpiration), and molecular (relative expression of nitrate transporters and aquaporins) parameters. Only plants given 4 mM N showed a reduction in growth. Although there were changes in NR activity, protein synthesis, and chlorophyll content in both 8 and 4 mM N plants that were highly related to aquaporin and nitrate transporter expression. The results revealed new findings on the relationship between aquaporins and nitrate transporters in new leaves of Citrus, suggesting a mechanism for ensuring growth under low N when new tissues are being formed., (© 2023 The Authors. Plant Biology published by John Wiley & Sons Ltd on behalf of German Society for Plant Sciences, Royal Botanical Society of the Netherlands.)

Nitrate supply is fundamental to support shoot growth and crop performance, but the associated increase in stem height exacerbates the risks of lodging and yield losses. Despite their significance for agriculture, the mechanisms involved in the promotion of stem growth by nitrate remain poorly understood. Here, we show that the elongation of the hypocotyl of Arabidopsis thaliana , used as a model, responds rapidly and persistently to upshifts in nitrate concentration, rather than to the nitrate level itself. The response occurred even in shoots dissected from their roots and required NITRATE TRANSPORTER 1.1 (NRT1.1) in the phosphorylated state (but not NRT1.1 nitrate transport capacity) and NIN-LIKE PROTEIN 7 (NLP7). Nitrate increased PHYTOCHROME INTERACTING FACTOR 4 (PIF4) nuclear abundance by posttranscriptional mechanisms that depended on NRT1.1 and phytochrome B. In response to nitrate, PIF4 enhanced the expression of numerous SMALL AUXIN-UP RNA (SAUR) genes in the hypocotyl. The growth response to nitrate required PIF4, positive and negative regulators of its activity, including AUXIN RESPONSE FACTORs, and SAURs. PIF4 integrates cues from the soil (nitrate) and aerial (shade) environments adjusting plant stature to facilitate access to light.

A fully mechanistic dynamical model for plant nitrate uptake is presented. Based on physiological and regulatory pathways and based on physical laws, we form a dynamic system mathematically described by seven differential equations. The model evidences the presence of a short-term positive feedback on the high-affinity nitrate uptake, triggered by the presence of nitrate around the roots, which induces its intaking. In the long run, this positive feedback is overridden by two long-term negative feedback loops which drastically reduces the nitrate uptake capacity. These two negative feedbacks are due to the generation of ammonium and amino acids, respectively, and inhibit the synthesis and the activity of high-affinity nitrate transporters. This model faithfully predicts the typical spiking behavior of the nitrate uptake, in which an initial strong increase of nitrate absorption capacity is followed by a drop, which regulates the absorption down to the initial value. The model outcome was compared with experimental data and they fit quite nicely. The model predicts that after the initial exposure of the roots with nitrate, the absorption of the anion strongly increases and that, on the contrary, the intensity of the absorption is limited in presence of ammonium around the roots., (© 2023 The Authors. Physiologia Plantarum published by John Wiley & Sons Ltd on behalf of Scandinavian Plant Physiology Society.)