The Expression Characteristics of NPF Genes and Their Response to Vernalization and Nitrogen Deficiency in Rapeseed

The Role of Chloride Channels in Plant Responses to NaCl

Chloride (Cl-) is considered a crucial nutrient for plant growth, but it can be a challenge under saline conditions. Excessive accumulation of Cl- in leaves can cause toxicity. Chloride channels (CLCs) are expressed in the inner membranes of plant cells and function as essential Cl- exchangers or channels. In response to salt stress in plants, CLCs play a crucial role, and CLC proteins assist in maintaining the intracellular Cl- homeostasis by sequestering Cl- into vacuoles. Sodium chloride (NaCl) is the primary substance responsible for causing salt-induced phytotoxicity. However, research on plant responses to Cl- stress is comparatively rare, in contrast to that emphasizing Na+. This review provides a comprehensive overview of the plant response and tolerance to Cl- stress, specifically focusing on comparative analysis of CLC protein structures in different species. Additionally, to further gain insights into the underlying mechanisms, the study summarizes the identified CLC genes that respond to salt stress. This review provides a comprehensive overview of the response of CLCs in terrestrial plants to salt stress and their biological functions, aiming to gain further insights into the mechanisms underlying the response of CLCs in plants to salt stress.

Genome-Wide Identification of the NRT1 Family Members and Their Expression under Low-Nitrate Conditions in Chinese Cabbage (Brassica rapa L. ssp. pekinensis)

Nitrate transporters (NRTs) actively take up and transform nitrate (N) to form a large family with many members and distinct functions in plant growth and development. However, few studies have identified them in the context of low nitrate concentrations in Chinese cabbage (Brassica rapa L. ssp. Pekinensis), an important vegetable in China. This study focuses on the identification and analysis of the nitrate transporter 1 (NRT1) gene family as well as various aspects, including its phylogenic distribution, chromosomal position, gene structure, conserved motifs, and duplication pattern. Using bioinformatics methods, we identified and analyzed 84 BrNRT1 genes distributed on ten chromosomes. Furthermore, we conducted an analysis of the expression profile of the NRT1 gene in various tissues of Chinese cabbage exposed to varying nitrate concentrations. A phylogenetic analysis revealed that BrNRT1s members are distributed in six distinct groups. Based on an analysis of gene structure and conserved motifs, it can be inferred that BrNRT1 exhibits a generally conserved structural pattern. The promoters of BrNRT1 were discovered to contain moosefs (MFS) elements, suggesting their potential role in the regulation of NO3- transport across the cell membrane in Chinese cabbage. A transcriptome study and a subsequent RT-qPCR analysis revealed that the expression patterns of some BrNRT1 genes were distinct to specific tissues. This observation implies these genes may contribute to nitrate uptake and transport in various tissues or organs. The results offer fundamental insights into investigating the NRT1 gene family in Chinese cabbage. These results provide basic information for future research on the functional characterization of NRT1 genes in Chinese cabbage and the elucidation of the molecular mechanisms underlying low nitrogen tolerance in Chinese cabbage.

Exploring the genetic landscape of nitrogen uptake in durum wheat: genome-wide characterization and expression profiling of NPF and NRT2 gene families

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.

Integrated approaches for increasing plant yield under salt stress

Salt stress affects large cultivated areas worldwide, thus causing remarkable reductions in plant growth and yield. To reduce the negative effects of salt stress on plant growth and yield, plant hormones, nutrient absorption, and utilization, as well as developing salt-tolerant varieties and enhancing their morpho-physiological activities, are some integrative approaches to coping with the increasing incidence of salt stress. Numerous studies have been conducted to investigate the critical impacts of these integrative approaches on plant growth and yield. However, a comprehensive review of these integrative approaches, that regulate plant growth and yield under salt stress, is still in its early stages. The review focused on the major issues of nutrient absorption and utilization by plants, as well as the development of salt tolerance varieties under salt stress. In addition, we explained the effects of these integrative approaches on the crop's growth and yield, illustrated the roles that phytohormones play in improving morpho-physiological activities, and identified some relevant genes involve in these integrative approaches when the plant is subjected to salt stress. The current review demonstrated that HA with K enhance plant morpho-physiological activities and soil properties. In addition, NRT and NPF genes family enhance nutrients uptake, NHX1, SOS1, TaNHX, AtNHX1, KDML, RD6, and SKC1, maintain ion homeostasis and membrane integrity to cope with the adverse effects of salt stress, and sd1/Rht1, AtNHX1, BnaMAX1s, ipal-1D, and sft improve the plant growth and yield in different plants. The primary purpose of this investigation is to provide a comprehensive review of the performance of various strategies under salt stress, which might assist in further interpreting the mechanisms that plants use to regulate plant growth and yield under salt stress.

Short-term transcriptomic analysis at organ scale reveals candidate genes involved in low N responses in NUE-contrasting tomato genotypes

BACKGROUND

Understanding the complex regulatory network underlying plant nitrogen (N) responses associated with high Nitrogen Use Efficiency (NUE) is one of the main challenges for sustainable cropping systems. Nitrate (NO₃ ^-), acting as both an N source and a signal molecule, provokes very fast transcriptome reprogramming, allowing plants to adapt to its availability. These changes are genotype- and tissue-specific; thus, the comparison between contrasting genotypes is crucial to uncovering high NUE mechanisms.

METHODS

Here, we compared, for the first time, the spatio-temporal transcriptome changes in both root and shoot of two NUE contrasting tomato genotypes, Regina Ostuni (high-NUE) and UC82 (low-NUE), in response to short-term (within 24 h) low (LN) and high (HN) NO₃ ^- resupply.

RESULTS

Using time-series transcriptome data (0, 8, and 24 h), we identified 395 and 482 N-responsive genes differentially expressed (DEGs) between RO and UC82 in shoot and root, respectively. Protein kinase signaling plant hormone signal transduction, and phenylpropanoid biosynthesis were the main enriched metabolic pathways in shoot and root, respectively, and were upregulated in RO compared to UC82. Interestingly, several N transporters belonging to NRT and NPF families, such as NRT2.3, NRT2.4, NPF1.2, and NPF8.3, were found differentially expressed between RO and UC82 genotypes, which might explain the contrasting NUE performances. Transcription factors (TFs) belonging to several families, such as ERF, LOB, GLK, NFYB, ARF, Zinc-finger, and MYB, were differentially expressed between genotypes in response to LN. A complementary Weighted Gene Co-expression Network Analysis (WGCNA) allowed the identification of LN-responsive co-expression modules in RO shoot and root. The regulatory network analysis revealed candidate genes that might have key functions in short-term LN regulation. In particular, an asparagine synthetase (ASNS), a CBL-interacting serine/threonine-protein kinase 1 (CIPK1), a cytokinin riboside 5'-monophosphate phosphoribohydrolase (LOG8), a glycosyltransferase (UGT73C4), and an ERF2 were identified in the shoot, while an LRR receptor-like serine/threonine-protein kinase (FEI1) and two TFs NF-YB5 and LOB37 were identified in the root.

DISCUSSION

Our results revealed potential candidate genes that independently and/or concurrently may regulate short-term low-N response, suggesting a key role played by cytokinin and ROS balancing in early LN regulation mechanisms adopted by the N-use efficient genotype RO.

Unlocking the potentials of nitrate transporters at improving plant nitrogen use efficiency

Nitrate ( NO 3 - ) 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 NO 3 - transporters. To better understand how these transporters function in improving plant NUE, this review critically examined the roles of NO 3 - 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 NO 3 - 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.

The cassava (Manihot-esculenta Crantz)'s nitrate transporter NPF4.5, expressed in seedling roots, involved in nitrate flux and osmotic stress

AtNPF4.5/AIT2, which was predicted to be a low-affinity transporter capable for nitrate uptake, was screened by ABA receptor complex in Arabidopsis ten years ago. However, the molecular and biochemical characterizations of AtNPF4.5 in plants remained largely unclear. In this study, the function of a plasma-membrane-localized and root-specifically-expressed gene MeNPF4.5 (Manihot-esculenta NITRATE TRANSPORTER 1 PTR FAMILY4.5), an ortholog of the Arabidopsis thaliana NPF4.5, was investigated in cassava roots as a nitrate efflux transporter on low nitrate medium and an influx transporter following exposure to high concentration of external nitrates. Moreover, RNA interference (RNAi) of MeNPF4.5 reduced the nitrate efflux capacity but the overexpressing cassava seedlings increased the ability of efflux from the elongation to the mature zone of root under low nitrate treatments. Besides, MeNPF4.5-RNAi expression reduced the nitrate influx capacity but enhanced nitrate absorption in parts of overexpressing plants from the meristem, elongation to mature zone of roots under high nitrate conditions. Furthermore, MeNPF4.5-RNAi seedlings survived owing to roots that could grow normally, but the MeNPF4.5-over-expressors showed adverse growth under 7% PEG6000 stress, suggesting that MeNPF4.5 negatively regulated the osmotic stress and was involved in nitrate flux through cassava seedlings.

Identification of NPF Family Genes in Brassica rapa Reveal Their Potential Functions in Pollen Development and Response to Low Nitrate Stress

Nitrate Transporter 1/Peptide Transporter Family (NPF) genes encode membrane transporters involved in the transport of diverse substrates. However, little is known about the diversity and functions of NPFs in Brassica rapa. In this study, 85 NPFs were identified in B. rapa (BrNPFs) which comprised eight subfamilies. Gene structure and conserved motif analysis suggested that BrNFPs were conserved throughout the genus. Stress and hormone-responsive cis-acting elements and transcription factor binding sites were identified in BrNPF promoters. Syntenic analysis suggested that tandem duplication contributed to the expansion of BrNPFs in B. rapa. Transcriptomic profiling analysis indicated that BrNPF2.6, BrNPF2.15, BrNPF7.6, and BrNPF8.9 were expressed in fertile floral buds, suggesting important roles in pollen development. Thirty-nine BrNPFs were responsive to low nitrate availability in shoots or roots. BrNPF2.10, BrNPF2.19, BrNPF2.3, BrNPF5.12, BrNPF5.16, BrNPF5.8, and BrNPF6.3 were only up-regulated in roots under low nitrate conditions, indicating that they play positive roles in nitrate absorption. Furthermore, many genes were identified in contrasting genotypes that responded to vernalization and clubroot disease. Our results increase understanding of BrNPFs as candidate genes for genetic improvement studies of B. rapa to promote low nitrate availability tolerance and for generating sterile male lines based on gene editing methods.

Physiological Responses of Cigar Tobacco Crop to Nitrogen Deficiency and Genome-Wide Characterization of the NtNPF Family Genes

Tobacco prefers nitrate as a nitrogen (N) source. However, little is known about the molecular components responsible for nitrate uptake and the physiological responses of cigar tobacco to N deficiency. In this study, a total of 117 nitrate transporter 1 (NRT1) and peptide transporter (PTR) family (NPF) genes were comprehensively identified and systematically characterized in the whole tobacco genome. The NtNPF members showed significant genetic diversity within and across subfamilies but showed conservation between subfamilies. The NtNPF genes are dispersed unevenly across the chromosomes. The phylogenetic analysis revealed that eight subfamilies of NtNPF genes are tightly grouped with their orthologues in Arabidopsis. The promoter regions of the NtNPF genes had extensive cis-regulatory elements. Twelve core NtNPF genes, which were strongly induced by N limitation, were identified based on the RNA-seq data. Furthermore, N deprivation severely impaired plant growth of two cigar tobaccos, and CX26 may be more sensitive to N deficiency than CX14. Moreover, 12 hub genes respond differently to N deficiency between the two cultivars, indicating the vital roles in regulating N uptake and transport in cigar tobacco. The findings here contribute towards a better knowledge of the NtNPF genes and lay the foundation for further functional analysis of cigar tobacco.

The emerging role of the nitrate and peptide transporter family: NPF in plant specialized metabolism

The nitrate and peptide transporter family (NPF) is one of the largest transporter families in the plant kingdom. The name of the family reflects the substrates (nitrate and peptides) identified for the two founding members CHL1 and PTR2 from Arabidopsis thaliana almost 30 years ago. However, since then, the NPF has emerged as a hotspot for transporters with a wide range of crucial roles in plant specialized metabolism. Recent prominent examples include 1) controlling accumulation of antinutritional glucosinolates in Brassica seeds, 2) deposition of heat-stress tolerance flavonol diglucosides to pollen coats 3) production of anti-cancerous monoterpene indole alkaloid precursors in Catharanthus roseus and 4) detoxification of steroid glycoalkaloids in ripening tomatoes. In this review, we turn the spotlight on the emerging role of the NPF in plant specialized metabolism and its potential for improving crop traits through transport engineering.

MdMKK9-Mediated the Regulation of Anthocyanin Synthesis in Red-Fleshed Apple in Response to Different Nitrogen Signals

The mitogen-activated protein kinase (MAPK) signaling cascade is a widely existing signal transduction system in eukaryotes, and plays an important role in the signal transduction processes of plant cells in response to environmental stress. In this study, we screened MdMKK9, a gene in the MAPK family. This gene is directly related to changes in anthocyanin synthesis in the ‘Daihong’ variety of red-fleshed apple (Malus sieversii f neidzwetzkyana (Dieck) Langenf). MdMKK9 expression was up-regulated in ‘Daihong’ tissue culture seedlings cultured at low levels of nitrogen. This change in gene expression up-regulated the expression of genes related to anthocyanin synthesis and nitrogen transport, thus promoting anthocyanin synthesis and causing the tissue culture seedlings to appear red in color. To elucidate the function of MdMKK9, we used the CRISPR/Cas9 system to construct a gene editing vector for MdMKK9 and successfully introduced it into the calli of the ‘Orin’ apple. The MdMKK9 deletion mutants (MUT) calli could not respond to the low level of nitrogen signal, the expression level of anthocyanin synthesis-related genes was down-regulated, and the anthocyanin content was lower than that of the wild type (WT). In contrast, the MdMKK9-overexpressed calli up-regulated the expression level of anthocyanin synthesis-related genes and increased anthocyanin content, and appeared red in conditions of low level of nitrogen or nitrogen deficiency. These results show that MdMKK9 plays a role in the adaptation of red-fleshed apple to low levels of nitrogen by regulating the nitrogen status and anthocyanin accumulation.

Systematic Investigation and Expression Profiles of the Nitrate Transporter 1/Peptide Transporter Family (NPF) in Tea Plant (Camellia sinensis)

NRT1/PTR FAMILY (NPF) genes are characterized as nitrate and peptide transporters that played important roles in various substrates transport in plants. However, little is known about the NPF gene in tea plants. Here, a total of 109 CsNPF members were identified from the tea plant genome, and divided into 8 groups according to their sequence characteristics and phylogenetic relationship. Gene structure and conserved motif analysis supported the evolutionary conservation of CsNPFs. Many hormone and stress response cis-acting elements and transcription factor binding sites were found in CsNPF promoters. Syntenic analysis suggested that multiple duplication types contributed to the expansion of NPF gene family in tea plants. Selection pressure analysis showed that CsNPF genes experienced strong purifying selective during the evolution process. The distribution of NPF family genes revealed that 8 NPF subfamilies were formed before the divergence of eudicots and monocots. Transcriptome analysis showed that CsNPFs were expressed differently in different tissues of the tea plant. The expression of 20 CsNPF genes at different nitrate concentrations was analyzed, and most of those genes responded to nitrate resupply. Subcellular localization showed that both CsNPF2.3 and CsNPF6.1 were localized in the plasma membrane, which was consistent with the characteristics of transmembrane proteins involved in NO₃^- transport. This study provides a theoretical basis for further investigating the evolution and function of NPF genes.