Expression Of Nitrate Transporters Research Articles

Involvement of plasma membrane H+-ATPase in the nitrate-nutrition uptake and utilization in indica rice

Utilization of nitrogen by crops is essential for sustainable agriculture. The transport of nitrate (NO3-) across the plasma membrane is a critical gateway for N uptake and subsequent utilization. This process requires proton (H+) coupled cotransport, which is driven by proton motive force, provided by plasma membrane (PM) H+-ATPase. In this report, two indica rice varieties [Meixiangzhan 2 (MXZ) and Jifengyou 1002 (JFY)] in South China were selected and cultivated in hydroponic solution with 0.5 mM or 2.0 mM NO3- as the N source. The JFY exhibited stronger growth with higher biomass than MXZ under both 0.5 mM and 2.0 mM NO3-. PM H+-ATPase activity of JFY roots was significantly higher than that of MXZ. The higher PM H+-ATPase activity in JFY was consistent with a higher abundance of PM H+-ATPase protein and higher transcription levels of OSAs, such as OSA2, OSA7 and OSA8 in roots, OSA3, OSA7 and OSA8 in leaves. The expression of nitrate transporters (OsNRT1;1b, OsNRT2.1, OsNRT2.2, and OsNAR2.1) were also higher in roots or shoots of JFY than those in MXZ. Under 0.5 mM and 2.0 mM NO3-, the NO3- absorption and translocation rate, nitrate content, as well as nitrate reductase (NR) activity were all significantly higher in JFY, as compared to those in MXZ. Taken together, in JFY and MXZ, a higher level of PM H+-ATPase protein and higher activity coupled with greater efficiency in nitrate uptake, translocation and assimilation, suggesting the existence of a close correlation between PM H+-ATPase and nitrate utilization in indica rice. PM H+-ATPase may one of the elite genes that can contribute to nitrate use efficiency in rice.

Microplastic exposure inhibits nitrate uptake and assimilation in wheat plants

Microplastic (MP) contamination in soil severely impairs plant growth. However, mechanisms underlying the effects of MPs on plant nutrient uptake remain largely unknown. In this study, we revealed that NO3− content was significantly decreased in shoots and roots of wheat plants exposed to high concentrations (50–100 mg L−1) of MPs (1 μm and 0.1 μm; type: polystyrene) in the hydroponic solution. Isotope labeling experiments demonstrated that MP exposure led to a significant inhibition of NO3− uptake in wheat roots. Further analysis indicated that the presence of MPs markedly inhibited root growth and caused oxidative damage to the roots. Additionally, superoxide dismutase and peroxidase activities in wheat roots decreased under all MP treatments, whereas catalase and ascorbate peroxidase activities significantly increased under the 100 mg L−1 MP treatment. The transcription levels of most nitrate transporters (NRTs) in roots were significantly downregulated by MP exposure. Furthermore, exposure to MPs distinctly suppressed the activity of nitrate reductase (NR) and nitrite reductase (NiR), as well as the expression levels of their coding genes in wheat shoots. These findings indicate that a decline in root uptake area and root vitality, as well as in the expression of NRTs, NR, and NiR genes caused by MP exposure may have adverse effects on NO3− uptake and assimilation, consequently impairing normal growth of plants.

Effects of low nitrogen supply on biochemical and physiological parameters related to nitrate and water, involving nitrate transporters and aquaporins in Citrus macrophylla.

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.

Seed characterization and early nitrogen metabolism performance of seedlings from Altiplano and coastal ecotypes of Quinoa

BackgroundEarly seed germination and a functional root system development during establishment are crucial attributes contributing to nutrient competence under marginal nutrient soil conditions. Chenopodium quinoa Willd (Chenopodiaceae) is a rustic crop, able to grow in marginal areas. Altiplano and Coastal/Lowlands are two representative zones of quinoa cultivation in South America with contrasting soil fertility and edaphoclimatic conditions.In the present work, we hypothesize that the ecotypes of Quinoa from Altiplano (landrace Socaire) and from Coastal/Lowland (landrace Faro) have developed differential adaptive responses in order to survive under conditions of low availability of N in their respective climatic zones of Altiplano and Lowlands. In order to understand intrinsic differences for N competence between landraces, seed metabolite profile and germinative capacity were studied. Additionally, in order to elucidate the mechanisms of N uptake and assimilation at limiting N conditions during establishment, germinated seeds of both landraces were grown at either sufficient nitrate (HN) or low nitrate (LN) supply. We studied the photosynthetic performance, protein storage, root morphometrical parameters, activity and expression of N-assimilating enzymes, and the expression of nitrate transporters of roots in plants submitted to the different treatments.ResultsSeeds from Socaire landrace presented higher content of free N-related metabolites and faster seed germination rate compared to Faro landrace. Seedlings of both ecotypes presented similar physiological performance at HN supply, but at LN supply their differences were exalted. At LN, Socaire plants showed an increased root biomass (including a higher number and total length of lateral roots), a differential regulation of a nitrate transporter (a NPF6.3-like homologue) belonging to the Low Affinity Transport System (LATS), and an upregulation of a nitrate transporter (a NRT2.1-like homologue) belonging to the High Affinity nitrate Transport System (HATS) compared to Faro. These responses as a whole could be linked to a higher amount of stored proteins in leaves, associated to an enhanced photochemical performance in Altiplano plants, in comparison to Lowland quinoa plants.ConclusionsThese differential characteristics of Socaire over Faro plants could involve an adaptation to enhanced nitrate uptake under the brutal unfavorable climate conditions of Altiplano.

Root extension and nitrate transporter up-regulation induced by nitrogen deficiency improves nitrogen status and plant growth at the seedling stage of winter wheat (Triticum aestivum L.)

Characterizing the responses of plant growth and nitrogen (N) uptake to low-nitrogen conditions will provide information towards elucidating the acclimation mechanism of N-efficient wheat seedlings. Two winter wheat cultivars, Yangmai158 (low-nitrate tolerant) and Zaoyangmai (low-nitrate sensitive), were supplied either 0.25mmolL−1 nitrate (low nitrate nutrition; LN) or 5mmolL−1 nitrate (control; CK), to investigate the responses of root morphology and nitrate transporter expression in a hydroponic experiment. Decreases in plant dry weight and N content were greater in Zaoyangmai than in Yangmai158, suggesting that Yangmai158 has a better growth status and N-storage ability in low-nitrate treatment. Additionally, root dry weight and uptake area increased to a greater extent in Yangmai158, especially in nodal roots. The decrement in nitrate concentration stimulated simultaneous upregulation of TaNRT1.1, TaNRT2.1 and TaNRT2.2 in Yangmai158, followed by upregulation of TaNAR2.1 in low-nitrate conditions. Plasma membrane H+-ATPase activity (PM H+-ATPase), which is involved in N-uptake energy supply, increased significantly in nodal roots of Yangmai158, consistent with increasing TaHA1 transcript abundance. Furthermore, the activities of nitrate reductase (NR) and glutamine synthetase (GS) were much higher in Yangmai158 initially, which could be a feedback signal for N-uptake. However, no difference of NR and GS activity between LN and CK was found in Zaoyangmai. These results suggest that larger root extension and nitrate transporter upregulation are the major reasons for the superior acclimation of Yangmai158 to nitrogen deficient growth conditions.

Daily transcriptome changes reveal the role of nitrogen in controlling microcystin synthesis and nutrient transport in the toxic cyanobacterium, Microcystis aeruginosa.

BackgroundWhile transcriptomics have become a valuable tool for linking physiology and ecology in aquatic microbes, the temporal dynamics of global transcriptomic patterns in Microcystis have rarely been assessed. Furthermore, while many microbial studies have explored expression of nutrient transporter genes, few studies have concurrently measured nutrient assimilation rates. Here, we considered how the global transcriptomic patterns and physiology of the cyanobacterium, Microcystis aeruginosa, changed daily as cells were grown from replete to deficient nitrogen (N) conditions and then back to replete conditions.ResultsDuring N deprivation, Microcystis downregulated genes involved in photosynthesis and respiration, carbon acquisition, lipid metabolism, and amino acid biosynthesis while upregulating genes involved in N acquisition and transport. With increasing N stress, both the strength of expression and number of genes being differentially expressed increased, until N was restored at which point these patterns reversed. Uptake of 15N-labeled nitrate, ammonium and urea reflected differential expression of genes encoding transporters for these nutrients, with Microcystis appearing to preferentially increase transcription of ammonium and urea transporters and uptake of these compounds during N deprivation. Nitrate uptake and nitrate transporter expression were correlated for one set of transporters but not another, indicating these were high and low affinity nitrate transporters, respectively. Concentrations of microcystin per cell decreased during N deprivation and increased upon N restoration. However, the transcript abundance of genes involved in the synthesis of this compound was complex, as microcystin synthetase genes involved in peptide synthesis were downregulated under N deprivation while genes involved in tailoring and transport were upregulated, suggesting modification of the microcystin molecule under N stress as well as potential alternative functions for these genes and/or this toxin.ConclusionsCollectively, this study highlights the complex choreography of gene expression, cell physiology, and toxin synthesis that dynamic N levels can elicit in this ecologically important cyanobacterium. Differing expression patterns of genes within the microcystin synthetase operon in response to changing N levels revealed the potential limitations drawing conclusions based on only one gene in this operon.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2275-9) contains supplementary material, which is available to authorized users.

Phospholipase Dε enhances Braasca napus growth and seed production in response to nitrogen availability.

Phospholipase D (PLD), which hydrolyses phospholipids to produce phosphatidic acid, has been implicated in plant response to macronutrient availability in Arabidopsis. This study investigated the effect of increased PLDε expression on nitrogen utilization in Brassica napus to explore the application of PLDε manipulation to crop improvement. In addition, changes in membrane lipid species in response to nitrogen availability were determined in the oil seed crop. Multiple PLDε over expression (PLDε-OE) lines displayed enhanced biomass accumulation under nitrogen-deficient and nitrogen-replete conditions. PLDε-OE plants in the field produced more seeds than wild-type plants but have no impact on seed oil content. Compared with wild-type plants, PLDε-OE plants were enhanced in nitrate transporter expression, uptake and reduction, whereas the activity of nitrite reductase was higher under nitrogen-depleted, but not at nitrogen-replete conditions. The level of nitrogen altered membrane glycerolipid metabolism, with greater impacts on young than mature leaves. The data indicate increased expression of PLDε has the potential to improve crop plant growth and production under nitrogen-depleted and nitrogen-replete conditions.

Investigation on mortality after corrosive ingestion: A prospective study

Characterizing the responses of plant growth and nitrogen (N) uptake to low-nitrogen conditions will provide information towards elucidating the acclimation mechanism of N-efficient wheat seedlings. Two winter wheat cultivars, Yangmai158 (low-nitrate tolerant) and Zaoyangmai (low-nitrate sensitive), were supplied either 0.25 mmol L−1 nitrate (low nitrate nutrition; LN) or 5 mmol L−1 nitrate (control; CK), to investigate the responses of root morphology and nitrate transporter expression in a hydroponic experiment. Decreases in plant dry weight and N content were greater in Zaoyangmai than in Yangmai158, suggesting that Yangmai158 has a better growth status and N-storage ability in low-nitrate treatment. Additionally, root dry weight and uptake area increased to a greater extent in Yangmai158, especially in nodal roots. The decrement in nitrate concentration stimulated simultaneous upregulation of TaNRT1.1, TaNRT2.1 and TaNRT2.2 in Yangmai158, followed by upregulation of TaNAR2.1 in low-nitrate conditions. Plasma membrane H+-ATPase activity (PM H+-ATPase), which is involved in N-uptake energy supply, increased significantly in nodal roots of Yangmai158, consistent with increasing TaHA1 transcript abundance. Furthermore, the activities of nitrate reductase (NR) and glutamine synthetase (GS) were much higher in Yangmai158 initially, which could be a feedback signal for N-uptake. However, no difference of NR and GS activity between LN and CK was found in Zaoyangmai. These results suggest that larger root extension and nitrate transporter upregulation are the major reasons for the superior acclimation of Yangmai158 to nitrogen deficient growth conditions.

NITRATE TRANSPORTER GENES FROM THE DIATOM CYLINDROTHECA FUSIFORMIS (BACILLARIOPHYCEAE): mRNA LEVELS CONTROLLED BY NITROGEN SOURCE AND BY THE CELL CYCLE.

The molecular characterization of components involved in nitrate uptake and assimilation in phytoplankton is likely to provide new insights into these processes, their regulation, and their effect on primary production. We report the cloning and initial characterization of the first nitrate transporter genes in a marine organism, from the diatom Cylindrotheca fusiformis Reimann et Lewin. A clone isolated from a silicon-responsive cDNA library was shown by sequence comparison to encode a homolog of high-affinity nitrate transporters. The C. fusiformis nitrate transporter cDNA was named NAT (NitrAte Transporter). The NAT cDNA was used to isolate a genomic clone that contained two additional nitrate transporter genes, NAT1 and NAT2, arranged in tandem. The cDNA and two genomic sequences were highly conserved, and only 18 of 1446 nucleotides in the coding region differed. At least four copies of NAT genes were present in C. fusiformis and as shown by hybridization, multiple copies were present in other diatom species. The transcript abundance of NAT genes in cultures with different nitrogen sources was monitored by RNase protection assays. NAT mRNA levels were high in the presence of nitrate, at nearly the same level during nitrogen starvation, and also high in urea-containing cultures. Lower mRNA levels occurred in nitrite-grown cultures. NAT transcript levels were highly repressed with NH4 Cl or NH4 NO3 as the nitrogen source, although very low amounts were detected. These results suggested that monitoring NAT mRNA levels could serve as a marker for (1) nitrate uptake in nitrate medium, (2) nitrogen starvation, and (3) ammonium use by virtue of absence of expression. NAT mRNA levels were not directly regulated by light or dark, but were apparently related to cellular growth and protein synthesis. Using light/dark synchronized cultures to monitor cell cycle responses, NAT mRNA levels were high in early G1 phase, decreased through the remainder of G1 , then increased during DNA synthesis in S phase and into G2 , and finally decreased after M phase. In silicon-starvation synchronized cultures, levels were high at the G1 /S phase boundary, high throughout S and G2 , and finally decreased after M phase. It was clear that NAT expression, and by inference nitrate uptake, did not occur at continuous levels throughout the cell cycle. The results of the RNase protection experiments suggested that transcriptional regulation is a major contributing factor in the control of diatom nitrate uptake. The cloning of the C. fusiformis nitrate transporter genes provides a new tool for investigating diatom nitrogen uptake and metabolism. In addition, the regulation of NAT expression by nitrogen source is likely to be useful in developing techniques to specifically control the expression of genes fused to NAT regulatory sequences in transgenic diatoms.