Project description:Dipeptide (Leu-Leu) and nitrate transport activities of 26 Arabidopsis NPF (NRT1/PTR Family) proteins were screened in Saccharomyces cerevisiae and Xenopus laevis oocytes, respectively. Dipeptide transport activity has been confirmed for 2 already known dipeptide transporters (AtNPF8.1 and AtNPF8.3) but none of the other tested NPFs displays dipeptide transport. The nitrate transport screen resulted in the identification of two new nitrate transporters, AtNPF5.5 and AtNPF5.10. The localization of the mRNA coding for NPF5.5 demonstrates that it is the first NPF transporter reported to be expressed in Arabidopsis embryo. Two independent homozygous npf5.5 KO lines display reduced total nitrogen content in the embryo as compared to WT plants, demonstrating an effect of NPF5.5 function on the embryo nitrogen content. Finally, NPF5.5 gene produces two different transcripts (AtNPF5.5a and AtNPF5.5b) encoding proteins with different N-terminal ends. Both proteins are able to transport nitrate in xenopus oocytes.
Project description:This study is measuring the steady-state levels of mRNA in wild-type Caulobacter crescentus grown in M2 defined medium containing either ammonium or nitrate as the sole nitrogen source.
Project description:Background: Nitrate plays an important role in grapevines vegetative and reproductive development. However, how grapevines uptake, translocate and utilize nitrate and the molecular mechanism still remains to be investigated.Results: In this study, we report the functional characterization of VvNPF6.5, a member of nitrate transporter 1/peptide transporter family (NRT1/PTR/NPF) in Vitis vinifera. Subcellular localization in Arabidopsis protoplasts indicated that VvNPF6.5 is plasma membrane localized. Quantitative RT-PCR analysis indicated that VvNPF6.5 is expressed predominantly in roots and stems and its expression is rapidly induced by nitrate. Functional characterization using cRNA-injected Xenopus laevis oocytes showed that VvNPF6.5 uptake nitrate in a pH dependent way and function as a dual-affinity nitrate transporter involved in both high- and low-affinity nitrate uptake. Further ectopic expression of VvNPF6.5 in Arabidopsis resulted in more 15NO3- accumulation in shoots and roots and significantly improved nitrogen use efficiency (NUE). Moreover, VvNPF6.5 might participate in the nitrate signaling by positively regulating the expression of primary nitrate response genes.Conclusion: Our results suggested that VvNPF6.5 encodes a pH-dependent, dual-affinity nitrate transporter. VvNPF6.5 regulates nitrate uptake and allocation in grapevines and is involved in primary nitrate response.
Project description:This study is measuring the steady-state levels of mRNA in wild-type Caulobacter crescentus grown in M2 defined medium containing either ammonium or nitrate as the sole nitrogen source. Four independent cultures of Caulobacter crecentus were grown in each of two medium conditions: M2(nitrate)glucose and M2(ammonium)glucose. Cultures in each medium type were grown to OD660=0.3 and RNA was isolated from each.
Project description:Nitrogen (N) is an essential macronutrient for plant growth. Plants absorb and utilize N mainly in the form of nitrate (NO3-) or ammonium (NH4+). In this study, the nitrate transporter DsNRT3.1 (also known as the nitrate assimilation-related protein DsNAR2.1) was characterized from Dianthus spiculifolius. A quantitative PCR (qPCR) analysis showed that the DsNRT3.1 expression was induced by NO3-. Under N-starvation conditions, the transformed Arabidopsis seedlings expressing DsNRT3.1 had longer roots and a greater fresh weight than the wild type. Subcellular localization showed that DsNRT3.1 was mainly localized to the plasma membrane in Arabidopsis root hair cells. Non-invasive micro-test (NMT) monitoring showed that the root hairs of N-starved transformed Arabidopsis seedlings had a stronger NO3- and NH4+ influx than the wild-type seedlings, using with NO3- or NH4+ as the sole N source; contrastingly, transformed seedlings only had a stronger NO3- influx when NO3- and NH4+ were present simultaneously. In addition, the qPCR analysis showed that the expression of AtNRT2 genes (AtNRT2.1-2.6), and particularly of AtNRT2.5, in the transformed Arabidopsis differed from that in the wild type. Overall, our results suggest that the heterologous expression of DsNRT3.1 affects seedlings' growth by enhancing the NO3- and NH4+ uptake in N-starved Arabidopsis. This may be related to the differential expression of AtNRT2 genes.
Project description:Ammonium nutrition often represents an important growth-limiting stress in plants. Some of the symptoms that plants present under ammonium nutrition have been associated with pH deregulation, in fact external medium pH control is known to improve plants ammonium tolerance. However, the way plant cell metabolism adjusts to these changes is not completely understood. Thus, in this work we focused on how Arabidopsis thaliana shoot and root respond to different nutritional regimes by varying the nitrogen source ([Formula: see text] and [Formula: see text]), concentration (2 and 10 mM) and pH of the external medium (5.7 and 6.7) to gain a deeper understanding of cell metabolic adaptation upon altering these environmental factors. The results obtained evidence changes in the response of ammonium assimilation machinery and of the anaplerotic enzymes associated to Tricarboxylic Acids (TCA) cycle in function of the plant organ, the nitrogen source and the degree of ammonium stress. A greater stress severity at pH 5.7 was related to [Formula: see text] accumulation; this could not be circumvented in spite of the stimulation of glutamine synthetase, glutamate dehydrogenase, and TCA cycle anaplerotic enzymes. Moreover, this study suggests specific functions for different gln and gdh isoforms based on the nutritional regime. Overall, [Formula: see text] accumulation triggering ammonium stress appears to bear no relation to nitrogen assimilation impairment.
Project description:Nitrate is the major nitrogen sources for higher plants. In addition to serving not only as a nutrient, it is also a signaling molecule that regulates plant growth and development. Although membrane-bound nitrate transporter/peptide transporters (NRT/PTR) have been extensively studied and shown to regulate nitrate uptake and movement, little is known about how these factors are regulated by the external nitrogen environment. Red flesh apple, the coloration of which is determined by the transcription factor MdMYB10, had higher nitrate uptake efficiency than non-red flesh apple. Nitrate assimilation and utilization were increased in red flesh apple cultivar, and comparative transcriptome analysis showed that the expression of genes encoding the NRT2s was increased in red flesh apple. In vitro and in vivo experiments showed that MdMYB10 directly bound to the MdNRT2.4-1 promoter to transcriptionally activate its expression, resulting in enhanced nitrate uptake. MdMYB10 also controlled nitrate reallocation from old leaves to new leaves through MdNRT2.4-1. Overall, our findings provide novel insights into the mechanism by which MdMYB10 controls nitrate uptake and reallocation in apple, which facilitates adaptation to low nitrogen environment.
Project description:Plant nitrogen (N) use is a key component of the N cycle in terrestrial ecosystems. The supply of N to plants affects community species composition and ecosystem processes such as photosynthesis and carbon (C) accumulation. However, the availabilities and relative importance of different N forms to plants are not well understood. While nitrate (NO3-) is a major N form used by plants worldwide, it is discounted as a N source for Arctic tundra plants because of extremely low NO3- concentrations in Arctic tundra soils, undetectable soil nitrification, and plant-tissue NO3- that is typically below detection limits. Here we reexamine NO3- use by tundra plants using a sensitive denitrifier method to analyze plant-tissue NO3- Soil-derived NO3- was detected in tundra plant tissues, and tundra plants took up soil NO3- at comparable rates to plants from relatively NO3--rich ecosystems in other biomes. Nitrate assimilation determined by 15N enrichments of leaf NO3- relative to soil NO3- accounted for 4 to 52% (as estimated by a Bayesian isotope-mixing model) of species-specific total leaf N of Alaskan tundra plants. Our finding that in situ soil NO3- availability for tundra plants is high has important implications for Arctic ecosystems, not only in determining species compositions, but also in determining the loss of N from soils via leaching and denitrification. Plant N uptake and soil N losses can strongly influence C uptake and accumulation in tundra soils. Accordingly, this evidence of NO3- availability in tundra soils is crucial for predicting C storage in tundra.
Project description:Nitrate in plants is preferentially stored in vacuoles; however, how vacuolar nitrate is reallocated and to which biological process(es) it might contribute remain largely elusive. In this study, we functionally characterized three nitrate transporters NPF5.10, NPF5.14, and NPF8.5 that are tonoplast-localized. Ectopic expression in Xenopus laevis oocytes revealed that they mediate low-affinity nitrate transport. Histochemical analysis showed that these transporters were expressed preferentially in pericycle and xylem parenchyma cells. NPF5.10, NPF5.14, and NPF8.5 overexpression significantly decreased vacuolar nitrate contents and nitrate accumulation in Arabidopsis shoots. Further analysis showed that the sextuple mutant (npf5.10 npf5.14 npf8.5 npf5.11 npf5.12 npf5.16) had a higher 15NO3-uptake rate than the wild-type Col-0, but no significant difference was observed for nitrate accumulation between them. The septuple mutant (npf5.11 npf5.12 npf5.16 npf5.10 npf5.14 npf8.5 clca) generated by using CRISPR/Cas9 showed essentially decreased nitrate reallocation compared to wild type when exposed to nitrate starvation, though no further decrease was observed when compared to clca. Notably, NPF5.10, NPF5.14, and NPF8.5 as well as NPF5.11, NPF5.12, and NPF5.16 were consistently induced by mannitol, and more nitrate was detected in the sextuple mutant than in the wild type after mannitol treatment. These observations suggest that vacuolar nitrate efflux is regulated by several functional redundant nitrate transporters, and the reallocation might contribute to osmotic stress response other than mineral nutrition.
Project description:Nitrogen (N) fertilization is essential to maximize crop production. However, around half of the applied N is lost to the environment causing water and air pollution and contributing to climate change. Understanding the natural genetic and metabolic basis underlying plants N use efficiency is of great interest to reach an agriculture with less N demand and thus, more sustainable. The study of ammonium (NH4+) nutrition is of particular interest, because it mitigates N losses due to nitrate (NO3-) leaching or denitrification. In this work, we performed gene expression analysis in the root of the model plant for C3 grasses Brachypodiyum distachyon, reference accession Bd21, grown with exclusive NH4+ or NO3- supply.