Cadmium Toxicity Induced Changes in Nitrogen Management in Lycopersicon esculentum Leading to a Metabolic Safeguard Through an Amino Acid Storage Strategy

Chaffei, Chiraz; Pageau, Karine; Suzuki, Akira; Gouia, Houda; Ghorbel, Mohamed Habib; Masclaux-Daubresse, Céline

doi:10.1093/pcp/pch192

Cited by 261 publications

(166 citation statements)

References 53 publications

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“…The Role of NRT1.8-Regulated Nitrate Distribution under Cadmium Stress Cd 2+ , a nonessential toxic heavy metal, has long been observed to severely inhibit nitrate uptake, transport, and assimilation (Sanita di Toppi and Gabbrielli, 1999), resulting in biomass and protein content reduction (Chaffei et al, 2004). Furthermore, Cd 2+ was also observed to affect nitrogen distribution in various plant species.…”

Section: Nrt18 Is An Essential Component Regulating Nitrate Distribumentioning

confidence: 99%

“…Furthermore, Cd 2+ was also observed to affect nitrogen distribution in various plant species. In Cd 2+ -treated tomato (Solanum lycopersicum) seedlings, the total amino acid content increased in phloem and roots, together with an increase of glutamate dehydrogenase, cytosolic glutamine synthetase, and asparagine synthetase expression, suggesting that nitrogen was recycled and translocated from shoots to roots as a Cd 2+ protection and storage strategy that may preserve roots (Chaffei et al, 2004).…”

Section: Nrt18 Is An Essential Component Regulating Nitrate Distribumentioning

confidence: 99%

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TheArabidopsisNitrate Transporter NRT1.8 Functions in Nitrate Removal from the Xylem Sap and Mediates Cadmium Tolerance

et al. 2010

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Long-distance transport of nitrate requires xylem loading and unloading, a successive process that determines nitrate distribution and subsequent assimilation efficiency. Here, we report the functional characterization of NRT1.8, a member of the nitrate transporter (NRT1) family in Arabidopsis thaliana. NRT1.8 is upregulated by nitrate. Histochemical analysis using promoter-β-glucuronidase fusions, as well as in situ hybridization, showed that NRT1.8 is expressed predominantly in xylem parenchyma cells within the vasculature. Transient expression of the NRT1.8:enhanced green fluorescent protein fusion in onion epidermal cells and Arabidopsis protoplasts indicated that NRT1.8 is plasma membrane localized. Electrophysiological and nitrate uptake analyses using Xenopus laevis oocytes showed that NRT1.8 mediates low-affinity nitrate uptake. Functional disruption of NRT1.8 significantly increased the nitrate concentration in xylem sap. These data together suggest that NRT1.8 functions to remove nitrate from xylem vessels. Interestingly, NRT1.8 was the only nitrate assimilatory pathway gene that was strongly upregulated by cadmium (Cd2+) stress in roots, and the nrt1.8-1 mutant showed a nitrate-dependent Cd2+-sensitive phenotype. Further analyses showed that Cd2+ stress increases the proportion of nitrate allocated to wild-type roots compared with the nrt1.8-1 mutant. These data suggest that NRT1.8-regulated nitrate distribution plays an important role in Cd2+ tolerance.

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Section: Nrt18 Is An Essential Component Regulating Nitrate Distribumentioning

confidence: 99%

Section: Nrt18 Is An Essential Component Regulating Nitrate Distribumentioning

confidence: 99%

TheArabidopsisNitrate Transporter NRT1.8 Functions in Nitrate Removal from the Xylem Sap and Mediates Cadmium Tolerance

et al. 2010

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“…Equal total amounts of 18S ribosomal RNA were used as the internal standard for RT (data Table I. Amino acid determination (% and total content) in phloem sap collected from tobacco leaves of different ages Amino acids were pooled prior to analysis, which was carried out according to Chaffei et al (2004). Numbers in parentheses correspond to the amino acid determination (% and total content) in leaf blades, determined as described by Masclaux et al (2000).…”

Section: Changes In the Levels Of Nitrogen Assimilatory Enzymes And Ementioning

confidence: 99%

“…Phloem exudates were collected from 10-week-old wild-type tobacco plants in the light period as described previously (Chaffei et al, 2004). Leaf petioles were excised and recut under water and rapidly immersed in 1 mL of collection buffer consisting of 10 mM HEPES, pH 7.5, and 1 mM EDTA.…”

Section: Phloem Sap Collectionmentioning

confidence: 99%

Glutamine Synthetase-Glutamate Synthase Pathway and Glutamate Dehydrogenase Play Distinct Roles in the Sink-Source Nitrogen Cycle in Tobacco

et al. 2006

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Glutamate (Glu) metabolism and amino acid translocation were investigated in the young and old leaves of tobacco (Nicotiana tabacum L. cv Xanthi) using [15N]ammonium and [2-15N]Glu tracers. Regardless of leaf age, [15N]ammonium assimilation occurred via glutamine synthetase (GS; EC 6.1.1.3) and Glu synthase (ferredoxin [Fd]-GOGAT; EC 1.4.7.1; NADH-GOGAT; EC 1.4.1.14), both in the light and darkness, and it did not depend on Glu dehydrogenase (GDH; EC 1.4.1.2). The [15N]ammonium and ammonium accumulation patterns support the role of GDH in the deamination of [2-15N]Glu to provide 2-oxoglutarate and [15N]ammonium. In the dark, excess [15N]ammonium was incorporated into asparagine that served as an additional detoxification molecule. The constant Glu levels in the phloem sap suggested that Glu was continuously synthesized and supplied into the phloem regardless of leaf age. Further study using transgenic tobacco lines, harboring the promoter of the GLU1 gene (encoding Arabidopsis [Arabidopsis thaliana] Fd-GOGAT) fused to a GUS reporter gene, revealed that the expression of Fd-GOGAT remained higher in young leaves compared to old leaves, and higher in the veins compared to the mesophyll. Confocal laser-scanning microscopy localized the Fd-GOGAT protein to the phloem companion cells-sieve element complex in the leaf veins. The results are consistent with a role of Fd-GOGAT in supplying Glu for the synthesis and transport of amino acids. Taken together, the data provide evidence that the GS-GOGAT pathway and GDH play distinct roles in the source-sink nitrogen cycle of tobacco leaves.

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“…The GS activity decrease in leaves was due to a lower content of the chloroplastic GS isoform (GS2) protein and transcripts, whereas the increase in GS activity in roots was related to the induction of the cytosolic GS isoform (GS1) protein and transcripts. 61 The significant increase in NH 4 + content in roots and leaves of HT relative to NT plants (Fig. 1C) was concomitant to a significant increase in the GDH activities (Fig.…”

Section: Plant Development and Biomass Allocationmentioning

confidence: 85%

Prolonged root hypoxia effects on enzymes involved in nitrogen assimilation pathway in tomato plants

Horchani

Aschi‐Smiti²

2010

Plant Signaling & Behavior

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IntroductionPlants grow in a dynamic environment, which frequently imposes constraints on growth and development. Among the adverse environmental factors commonly encountered by land plants, flooding is one of the most significant abiotic stresses. 1 Flooding of the soil can have a tremendous impact on the growth and survival of plants, and thereby on agricultural as well as natural ecosystems. In the last decades considerable progress has been made in our understanding of the mechanisms that enable certain plant species and cultivars to withstand periods with excess soil water or even complete submergence. Much of the research has been carried out with crop plant species, such as Oryza sativa, Zea mays, Trifolium subterraneum and Medicago sativa, 2-5 but wild species originating from wetland habitats have been also used, mostly for comparative studies. 6,7 With transient flooding or irrigation followed by slow drainage, or in natural wetlands, plant roots can become oxygen deficient because of slow transfer of dissolved oxygen in the waterfilled pore space of the soil. The decrease in ambient oxygen may not be, itself or alone, the perceived signal but could trigger metabolic responses, which then initiate the signalling cascade. 8 The immediate consequence of oxygen depletion is the reduction in respiration, thus diminishing ATP generation, and leading to a decrease in the ATP/ADP ratio and the adenylate energy charge. 9 In order to investigate the effects of root hypoxia (1-2% oxygen) on the nitrogen (N) metabolism of tomato plants (Solanum lycopersicum L. cv. Micro-Tom), a range of N compounds and N-assimilating enzymes were performed on roots and leaves of plants submitted to root hypoxia at the second leaf stage for three weeks. Obtained results showed that root hypoxia led to a significant decrease in dry weight (DW) production and nitrate content in roots and leaves. conversely, shoot to root DW ratio and nitrite content were significantly increased. contrary to that in leaves, glutamine synthetase activity was significantly enhanced in roots. The activities of nitrate and nitrite reductase were enhanced in roots as well as leaves. The higher increase in the Nh 4 + content and in the protease activities in roots and leaves of hypoxically treated plants coincide with a greater decrease in soluble protein contents. Taken together, these results suggest that root hypoxia leaded to higher protein degradation. The hypoxia-induced increase in the aminating glutamate dehydrogenase activity may be considered as an alternative N assimilation pathway involved in detoxifying the Nh 4 + , accumulated under hypoxic conditions. With respect to hypoxic stress, the distinct sensitivity of the enzymes involved in N assimilation is discussed. and 0.13 ± 0.03 g, respectively. The changes in the root and shoot dry weights (DW) and in shoot/root ratio were investigated after a three week period of hypoxic treatment. Root hypoxia decreased root and leaf DW production by 34 and 18%, respectively. Shoot to root DW ratio increas...

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Cadmium Toxicity Induced Changes in Nitrogen Management in Lycopersicon esculentum Leading to a Metabolic Safeguard Through an Amino Acid Storage Strategy

Cited by 261 publications

References 53 publications

TheArabidopsisNitrate Transporter NRT1.8 Functions in Nitrate Removal from the Xylem Sap and Mediates Cadmium Tolerance

TheArabidopsisNitrate Transporter NRT1.8 Functions in Nitrate Removal from the Xylem Sap and Mediates Cadmium Tolerance

Glutamine Synthetase-Glutamate Synthase Pathway and Glutamate Dehydrogenase Play Distinct Roles in the Sink-Source Nitrogen Cycle in Tobacco

Prolonged root hypoxia effects on enzymes involved in nitrogen assimilation pathway in tomato plants

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