氮是植物生长所需的三大主要营养元素之一，而硝态氮和铵态氮是植物吸收的2种主要氮素形态。硝态氮与铵态氮在植物生长过程中发挥着不同的作用。植物主要通过根系吸收硝态氮来满足生长过程中氮的需求，并转化为氨基酸、蛋白质等生物活性物质的合成原料，同时硝态氮参与叶绿素的合成，促进光合作用的进行；铵态氮也可被植物根系吸收，并用于植物体内蛋白质和氨基酸的合成，而且铵态氮的吸收速度较快，能够满足植物对氮素的迅速需求。由于植物生长特性不同，植物对硝态氮和铵态氮的利用效率有所差异。植物的基因型和环境因素都会影响其对不同氮素形态的利用能力，形成一些植物对硝态氮偏爱，而另一些植物则对铵态氮更为偏爱。本文从土壤氮素形态与转化影响因子、植物对氮素吸收机制以及高效氮素循环转化展望3个层面综述相关的研究进展，为作物生产中氮肥调控、土壤生态修复等科学研究提供技术理论参考依据。

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.© The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Plants have evolved to express some members of the nitrate transporter 1/peptide transporter family (NPF) to uptake and transport nitrate. However, little is known of the physiological and functional roles of this family in rice (Oryza sativa L.). Here, we characterized the vascular specific transporter OsNPF2.2. Functional analysis using cDNA-injected Xenopus laevis oocytes revealed that OsNPF2.2 is a low-affinity, pH-dependent nitrate transporter. Use of a green fluorescent protein tagged OsNPF2.2 showed that the transporter is located in the plasma membrane in the rice protoplast. Expression analysis showed that OsNPF2.2 is nitrate inducible and is mainly expressed in parenchyma cells around the xylem. Disruption of OsNPF2.2 increased nitrate concentration in the shoot xylem exudate when nitrate was supplied after a deprivation period; this result suggests that OsNPF2.2 may participate in unloading nitrate from the xylem. Under steady-state nitrate supply, the osnpf2.2 mutants maintained high levels of nitrate in the roots and low shoot:root nitrate ratios; this observation suggests that OsNPF2.2 is involved in root-to-shoot nitrate transport. Mutation of OsNPF2.2 also caused abnormal vasculature and retarded plant growth and development. Our findings demonstrate that OsNPF2.2 can unload nitrate from the xylem to affect the root-to-shoot nitrate transport and plant development.

Nitrate allocation in Arabidopsis (Arabidopsis thaliana) represents an important mechanism for mediating plant environmental adaptation. However, whether this mechanism occurs or has any physiological/agronomic importance in the ammoniphilic plant rice (Oriza sativa L.) remains unknown. Here, we address this question through functional characterization of the Nitrate transporter 1/Peptide transporter Family (NPF) transporter gene OsNPF7.9. Ectopic expression of OsNPF7.9 in Xenopus oocytes revealed that the gene encodes a low-affinity nitrate transporter. Histochemical and in-situ hybridization assays showed that OsNPF7.9 expresses preferentially in xylem parenchyma cells of vasculature tissues. Transient expression assays indicated that OsNPF7.9 localizes to the plasma membrane. Nitrate allocation from roots to shoots was essentially decreased in osnpf7.9 mutants. Biomass, grain yield, and nitrogen use efficiency (NUE) decreased in the mutant dependent on nitrate availability. Further analysis demonstrated that nitrate allocation mediated by OsNPF7.9 is essential for balancing rice growth and stress tolerance. Moreover, our research identified an indica–japonica divergent single-nucleotide polymorphism occurring in the coding region of OsNPF7.9, which correlates with enhanced nitrate allocation to shoots of indica rice, revealing that divergent nitrate allocation might represent an important component contributing to the divergent NUE between indica and japonica subspecies and was likely selected as a favorable trait during rice breeding.

Asian cultivated rice (Oryza sativa L.) consists of two main subspecies, indica and japonica. Indica has higher nitrate-absorption activity than japonica, but the molecular mechanisms underlying that activity remain elusive. Here we show that variation in a nitrate-transporter gene, NRT1.1B (OsNPF6.5), may contribute to this divergence in nitrate use. Phylogenetic analysis revealed that NRT1.1B diverges between indica and japonica. NRT1.1B-indica variation was associated with enhanced nitrate uptake and root-to-shoot transport and upregulated expression of nitrate-responsive genes. The selection signature of NRT1.1B-indica suggests that nitrate-use divergence occurred during rice domestication. Notably, field tests with near-isogenic and transgenic lines confirmed that the japonica variety carrying the NRT1.1B-indica allele had significantly improved grain yield and nitrogen-use efficiency (NUE) compared to the variety without that allele. Our results show that variation in NRT1.1B largely explains nitrate-use divergence between indica and japonica and that NRT1.1B-indica can potentially improve the NUE of japonica.

Abscisic acid (ABA) is the most crucial phytohormone for plants in adapting to environmental conditions. While the ABA signaling network in plants has been extensively explored, our understanding of the diverse ABA sensing systems remains limited. Here, we found that the transcriptional response to ABA is suppressed under high-nitrate conditions but substantially increases under low-nitrate conditions, suggesting a tight integration of ABA signaling with nutrient conditions. Interestingly, NRT1.1B, traditionally recognized as a nitrate transporter and receptor, exhibits a markedly higher affinity for ABA, leading to the formation of an ABA-facilitated NRT1.1B-SPX4 complex. This complex triggers the release of SPX4-sequestered transcription factor NLP4, thereby initiating the transcriptional response to ABA. These findings establish that NRT1.1B functions as an ABA receptor. Notably, the competitive binding of nitrate and ABA to NRT1.1B unveils a mechanism that enables a flexible ABA response to fluctuating nutrient conditions, illustrating a sophisticated strategy for integrating compound environmental cues.Copyright © 2025 Elsevier Inc. All rights reserved.

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.

NPF (formerly referred to as low-affinity NRT1) and 'high-affinity' NRT2 nitrate transporter genes are involved in nitrate uptake by the root, and transport and distribution of nitrate within the plant. The NPF gene family consists of 53 members in Arabidopsis thaliana, however only 11 of these have been functionally characterized. Although homologous genes have been identified in genomes of different plant species including some cereals, there is little information available for wheat (Triticum aestivum). Sixteen genes were identified in wheat homologous to characterized Arabidopsis low-affinity nitrate transporter NPF genes, suggesting a complex wheat NPF gene family. The regulation of wheat NFP genes by plant N-status indicated involvement of these transporters in substrate transport in relation to N-metabolism. The complex expression pattern in relation to tissue specificity, nitrate availability and senescence may be associated with the complex growth patterns of wheat depending on sink/source demands, as well as remobilization during grain filling. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Nitrogen transport is one of the most important processes in plants mediated by specialized transmembrane proteins. Plants have two main systems for nitrogen uptake from soil and its transport within the system-a low-affinity transport system and a high-affinity transport system. Nitrate transporters are of special interest in cereal crops because large amount of money is spent on N fertilizers every year to enhance the crop productivity. Till date four gene families of nitrate transporter proteins; NPF (nitrate transporter 1/peptide transporter family), NRT2 (nitrate transporter 2 family), the CLC (chloride channel family), and the SLAC/SLAH (slow anion channel-associated homologues) have been reported in plants. In our study, in silico mining of nitrate transporter genes along with their detailed structure, phylogenetic and expression analysis was carried out. A total of 412 nitrate transporter genes were identified in hexaploid wheat genome using HMMER based homology searches in IWGSC Refseq v2.0. Out of those twenty genes were root specific, 11 leaf/shoot specific and 17 genes were grain/spike specific. The identification of nitrate transporter genes in the close proximity to the previously identified 67 marker-traits associations associated with the nitrogen use efficiency related traits in nested synthetic hexaploid wheat introgression library indicated the robustness of the reported transporter genes. The detailed crosstalk between the genome and proteome and the validation of identified putative candidate genes through expression and gene editing studies may lay down the foundation to improve nitrogen use efficiency of cereal crops.© 2022. The Author(s).

Nitrate is both a nitrogen source for higher plants and a signal molecule regulating their development. In Arabidopsis, the NRT1.1 nitrate transporter is crucial for nitrate signaling governing root growth, and has been proposed to act as a nitrate sensor. However, the sensing mechanism is unknown. Herein we show that NRT1.1 not only transports nitrate but also facilitates uptake of the phytohormone auxin. Moreover, nitrate inhibits NRT1.1-dependent auxin uptake, suggesting that transduction of nitrate signal by NRT1.1 is associated with a modification of auxin transport. Among other effects, auxin stimulates lateral root development. Mutation of NRT1.1 enhances both auxin accumulation in lateral roots and growth of these roots at low, but not high, nitrate concentration. Thus, we propose that NRT1.1 represses lateral root growth at low nitrate availability by promoting basipetal auxin transport out of these roots. This defines a mechanism connecting nutrient and hormone signaling during organ development.Copyright 2010 Elsevier Inc. All rights reserved.

In Arabidopsis the plasma membrane nitrate transceptor (transporter/receptor) NRT1.1 governs many physiological and developmental responses to nitrate. Alongside facilitating nitrate uptake, NRT1.1 regulates the expression levels of many nitrate assimilation pathway genes, modulates root system architecture, relieves seed dormancy and protects plants from ammonium toxicity. Here, we assess the functional and phenotypic consequences of point mutations in two key residues of NRT1.1 (P492 and T101). We show that the point mutations differentially affect several of the NRT1.1-dependent responses to nitrate, namely the repression of lateral root development at low nitrate concentrations, and the short-term upregulation of the nitrate-uptake gene NRT2.1, and its longer-term downregulation, at high nitrate concentrations. We also show that these mutations have differential effects on genome-wide gene expression. Our findings indicate that NRT1.1 activates four separate signalling mechanisms, which have independent structural bases in the protein. In particular, we present evidence to suggest that the phosphorylated and non-phosphorylated forms of NRT1.1 at T101 have distinct signalling functions, and that the nitrate-dependent regulation of root development depends on the phosphorylated form. Our findings add to the evidence that NRT1.1 is able to trigger independent signalling pathways in Arabidopsis in response to different environmental conditions.

Acyl-lipids such as intracellular phospholipids, galactolipids, sphingolipids, and surface lipids play a crucial role in plant cells by serving as major components of cellular membranes, seed storage oils, and extracellular lipids such as cutin and suberin. Plant lipids are also widely used to make food, renewable biomaterials, and fuels. As such, enormous efforts have been made to uncover the specific roles of different genes and enzymes involved in lipid biosynthetic pathways over the last few decades. sn-Glycerol-3-phosphate acyltransferases (GPAT) are a group of important enzymes catalyzing the acylation of sn-glycerol-3-phosphate at the sn-1 or sn-2 position to produce lysophosphatidic acids. This reaction constitutes the first step of storage-lipid assembly and is also important in polar- and extracellular-lipid biosynthesis. Ten GPAT have been identified in Arabidopsis, and many homologs have also been reported in other plant species. These enzymes differentially localize to plastids, mitochondria, and the endoplasmic reticulum, where they have different biological functions, resulting in distinct metabolic fate(s) for lysophosphatidic acid. Although studies in recent years have led to new discoveries about plant GPAT, many gaps still exist in our understanding of this group of enzymes. In this article, we highlight current biochemical and molecular knowledge regarding plant GPAT, and also discuss deficiencies in our understanding of their functions in the context of plant acyl-lipid biosynthesis.© 2018 AOCS.

Autophagy is a conserved mechanism among eukaryotes that degrades and recycles cytoplasmic components. Autophagy is known to influence the plant metabolome, including lipid content; however, its impact on the plant lipidome is not fully understood, and most studies have analyzed a single or few mutants defective in autophagy. To gain more insight into the effect of autophagy on lipid concentrations and composition, we quantitatively profiled glycerolipids from multiple Arabidopsis thaliana mutants altered in autophagy and compared them with wild-type seedlings under nitrogen replete (+N; normal growth) and nitrogen starvation (−N; autophagy inducing) conditions. Mutants include those in genes of the core autophagy pathway, together with other genes that have been reported to affect autophagy. Using Matrix-Assisted Laser Desorption/Ionization—Mass Spectrometry (MALDI-MS), we imaged the cellular distribution of specific lipids in situ and demonstrated that autophagy and nitrogen treatment did not affect their spatial distribution within Arabidopsis seedling leaves. We observed changes, both increases and decreases, in the relative amounts of different lipid species in the mutants compared to WT both in +N and −N conditions, although more changes were seen in −N conditions. The relative amounts of polyunsaturated and very long chain lipids were significantly reduced in autophagy-disrupted mutants compared to WT plants. Collectively, our results provide additional evidence that autophagy affects plant lipid content and that autophagy likely affects lipid properties such as chain length and unsaturation.

Plants have developed complex mechanisms to perceive, transduce, and respond to environmental signals, such as light, which are essential for acquiring and allocating resources, including nitrogen (N). This review delves into the complex interaction between light signals and N metabolism, emphasizing light-mediated regulation of N uptake and assimilation. Firstly, we examine the details of light-mediated regulation of N uptake and assimilation, focusing on the light-responsive activity of nitrate reductase (NR) and nitrate transporters. Secondly, we discuss the influence of light on N-dependent developmental plasticity, elucidating how N availability regulates crucial developmental transitions such as flowering time, shoot branching, and root growth, as well as how light modulates these processes. Additionally, we consider the molecular interaction between light and N signalling, focusing on photoreceptors and transcription factors such as HY5, which are necessary for N uptake and assimilation under varying light conditions. A recent understanding of the nitrate signalling and perception of low N is also highlighted. The in silico transcriptome analysis suggests a reprogramming of N signalling genes by shade, and identifies NLP7, bZIP1, CPK30, CBL1, LBD37, LBD38, and HRS1 as crucial molecular regulators integrating light-regulated N metabolism.© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.

Carbon (C) and nitrogen (N) are fundamental elements essential for plant growth and development, serving as the structural and functional backbone of organic compounds and driving essential biological processes such as photosynthesis, carbohydrate metabolism, and N assimilation. The metabolism and transport of C involve the movement of sugars between shoots and roots through xylem and phloem transport systems, regulated by a sugar-signaling hub. Nitrogen uptake, transport, and metabolism are equally critical, with plants assimilating nitrate and ammonium through specialized transporters and enzymes in response to varying N levels to optimize growth and development. The coordination of C and N metabolism is key to plant productivity and the maintaining of agroecosystem stability. However, inefficient utilization of N fertilizers results in substantial environmental and economic challenges, emphasizing the urgent need to improve N use efficiency (NUE) in crops. Integrating efficient photosynthesis with N uptake offers opportunities for sustainable agricultural practices. This review discusses recent advances in understanding C and N transport, metabolism, and signaling in plants, with a particular emphasis on NUE-related genes in rice, and explores breeding strategies to enhance crop efficiency and agricultural sustainability.

Salicylic acid (SA) is a pivotal phytohormone for plant responses to biotic and abiotic stresses. Plants have evolved two pathways to produce SA: the isochorismate synthase and phenylalanine ammonia lyase (PAL) pathways 1. Whereas the isochorismate synthase pathway has been fully identified 2–4, the PAL pathway remains incomplete. Here we report the full characterization of the PAL pathway for SA biosynthesis via functional analysis of rice ( Oryza sativa ) SA-DEFICIENT GENE 1 ( OSD1 ) to OSD4. The cinnamoyl-coenzyme A (CoA) ligase OSD1 catalyses the conversion of trans -cinnamic acid to cinnamoyl-CoA, which is subsequently transformed to benzoyl-CoA via the β-oxidative pathway in peroxisomes. The resulting benzoyl-CoA is further converted to benzyl benzoate by the peroxisomal benzoyltransferase OSD2. Benzyl benzoate is subsequently hydroxylated to benzyl salicylate by the endoplasmic reticulum membrane-resident cytochrome P450 OSD3, which is ultimately hydrolysed to salicylic acid by the cytoplasmic carboxylesterase OSD4. Evolutionary analyses reveal that the PAL pathway was first assembled before the divergence of gymnosperms and has been conserved in most seed plants. Activation of the PAL pathway in rice significantly enhances salicylic acid levels and plant immunity. Completion of the PAL pathway provides critical insights into the primary salicylic acid biosynthetic pathway across plant species and offers a precise target for modulating crop immunity.\n

Orysa sativa pathogenesis-related protein 10a (OsPR10a) was induced by pathogens, salicylic acid (SA), jasmonic acid (JA), ethephon, abscisic acid (ABA), and NaCl. We tried to analyze the OsPR10a promoter to investigate the transcriptional regulation of OsPR10a by SA. We demonstrated the inducibility of OsPR10a promoter by SA using transgenic Arabidopsis carrying OsPR10a:GFP as well as by transient expression assays in rice. To further identify the promoter region responsible for its induction by SA, four different deletions of the OsPR10a promoter were made, and their activities were measured by transient assays. The construct containing 687-bp OsPR10a promoter from its start codon exhibited a six-fold increase of induction compared to the control in response to SA. Mutation in the W-box like element 1 (WLE 1) between 687 and 637-bp from TGACA to TGAAA completely abolished induction of the OsPR10a promoter by SA, indicating that the WLE 1 between −687 and −637 of OsPR10a promoter is important in SA-mediated OsPR10a expression. We show for the first time that the W-box like element plays a role in SA mediated PR gene expression.

Arabidopsis plants subjected to a daily dehydration stress and watered recovery cycle display physiological and transcriptional stress memory. Previously stressed plants have stomatal apertures that remain partially closed during a watered recovery period, facilitating reduced transpiration during a subsequent dehydration stress. Guard cells (GCs) display transcriptional memory that is similar to that in leaf tissues for some genes, but display GC-specific transcriptional memory for other genes. The rate-limiting abscisic acid (ABA) biosynthetic genes NINE-CIS-EPOXYCAROTENOID DIOXYGENASE 3 (NCED3) and ALDEHYDE OXIDASE 3 (AAO3) are expressed at much higher levels in GCs, particularly during the watered recovery interval, relative to their low levels in leaves. A genetic analysis using mutants in the ABA signaling pathway indicated that GC stomatal memory is ABA-dependent, and that ABA-dependent SNF1-RELATED PROTEIN KINASE 2.2 (SnRK2.2), SnRK2.3 and SnRK2.6 have distinguishable roles in the process. SnRK2.6 is more important for overall stomatal control, while SnRK2.2 and SnRK2.3 are more important for implementing GC stress memory in the subsequent dehydration response. Collectively, our results support a model of altered ABA production in GCs that maintains a partially closed stomatal aperture during an overnight watered recovery period. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Regulation of plant height and stem elongation has contributed significantly to improvement of cereal productivity by reducing lodging and improving distribution of assimilates to the inflorescence and grain. In wheat, genetic control of height has been largely contributed by the Reduced height-1 alleles that confer gibberellin insensitivity; the beneficial effects of these alleles are associated with less favourable effects involving seedling emergence, grain quality, and inflorescence architecture that have driven new research investigating genetic variation of stem growth. Here, we show that TEOSINTE BRANCHED1 (TB1) regulates height of wheat, with TB1 being expressed at low levels in nodes of the main culm prior to elongation, and increased dosage of TB1 restricting elongation of stem internodes. The effect of TB1 on stem growth is not accompanied by poor seedling emergence, as transgenic lines with increased activity of TB1 form longer coleoptiles than null transgenic controls. Analysis of height in a multiparent mapping population also showed that allelic variation for TB1 on the B genome influences height, with plants containing the variant TB-B1b allele being taller than those with the wild-type TB-B1a allele. Our results show that TB1 restricts height and stem elongation in wheat, suggesting that variant alleles that alter the expression or function of TB1 could be used as a new source of genetic diversity for optimizing architecture of wheat in breeding programmes.