Expression studies of <i>Nrt2:1Np</i>, a putative high‐affinity nitrate transporter: evidence for its role in nitrate uptake

Krapp, Anne; Fraisier, Vincent; Scheible, Wolf‐Rüdiger; Quesada, Alberto; Gojon, Alain; Stitt, Mark; Caboche, Michel; Daniel‐Vedele, Françoise

doi:10.1046/j.1365-313x.1998.00181.x

Cited by 149 publications

(146 citation statements)

References 46 publications

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“…After culture on NH 4 NO 3 solution, the plants were transferred for 7 days to a solution containing 1 mM NO 3 3 as sole N source. This treatment was expected to relieve AtNrt2.1 expression from repression by exogenous NH 4 in the wild-type [16,18]. In both genotypes, the kinetics of root 15 3 to determine the nitrate in£ux mediated by the HATS system.…”

Section: Isolation Of An Atnrt2 T-dna Insertion Mutantmentioning

confidence: 99%

An Arabidopsis T‐DNA mutant affected in Nrt2 genes is impaired in nitrate uptake

Filleur¹,

Dorbe²,

Cerezo³

et al. 2001

FEBS Letters

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Expression analyses of Nrt2 plant genes have shown a strict correlation with root nitrate influx mediated by the highaffinity transport system (HATS). The precise assignment of NRT2 protein function has not yet been possible due to the absence of heterologous expression studies as well as loss of function mutants in higher plants. Using a reverse genetic approach, we isolated an Arabidopsis thaliana knock-out mutant where the T-DNA insertion led to the complete deletion of the AtNrt2.1 gene together with the deletion of the 3P P region of the AtNrt2.2 gene. This mutant is impaired in the HATS, without being modified in the low-affinity system. Moreover, the deregulated expression of a Nicotiana plumbaginifolia Nrt2 gene restored the mutant nitrate influx to that of the wild-type. These results demonstrate that plant NRT2 proteins do have a role in HATS. ß

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Section: Isolation Of An Atnrt2 T-dna Insertion Mutantmentioning

confidence: 99%

An Arabidopsis T‐DNA mutant affected in Nrt2 genes is impaired in nitrate uptake

Filleur¹,

Dorbe²,

Cerezo³

et al. 2001

FEBS Letters

Self Cite

289

237

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“…This regulation is thought to be due to repression of NO 3 Ϫ and NH 4 ϩ transporters by reduced nitrogen metabolites accumulating in the tissues under satiety conditions (Jackson et al, 1986;Clarkson and Lü ttge, 1991;Lee et al, 1992;Muller and Touraine, 1992). Both NH 4 ϩ and amino acids were reported to exert this repression, also at the molecular level through inhibition of the expression of the Nrt2.1 and Amt1.1 genes (Krapp et al, 1998;Rawat et al, 1999;Zhuo et al, 1999;von Wirén et al, 2000b).…”

Section: The Atnrt2 Mutant Lacks the Hats Component Under Feedback Comentioning

confidence: 99%

Major Alterations of the Regulation of Root NO3 − Uptake Are Associated with the Mutation of Nrt2.1 and Nrt2.2 Genes in Arabidopsis

et al. 2001

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The role of AtNrt2.1 and AtNrt2.2 genes, encoding putative NO 3 Ϫ transporters in Arabidopsis, in the regulation of high-affinity NO 3 Ϫ uptake has been investigated in the atnrt2 mutant, where these two genes are deleted. Our initial analysis of the atnrt2 mutant (S. Filleur, M. Ϫ uptake is affected in this mutant due to the alteration of the high-affinity transport system (HATS), but not of the low-affinity transport system. In the present work, we show that the residual HATS activity in atnrt2 plants is not inducible by NO 3 Ϫ , indicating that the mutant is more specifically impaired in the inducible component of the HATS. Thus, high-affinity NO 3 Ϫ uptake in this genotype is likely to be due to the constitutive HATS. Root 15 NO 3 Ϫ influx in the atnrt2 mutant is no more derepressed by nitrogen starvation or decrease in the external NO 3 Ϫ availability. Moreover, the mutant also lacks the usual compensatory up-regulation of NO 3 Ϫ uptake in NO 3 Ϫ -fed roots, in response to nitrogen deprivation of another portion of the root system. Finally, exogenous supply of NH 4 ϩ in the nutrient solution fails to inhibit 15 NO 3 Ϫ influx in the mutant, whereas it strongly decreases that in the wild type. This is not explained by a reduced activity of NH 4 ϩ uptake systems in the mutant. These results collectively indicate that AtNrt2.1 and/or AtNrt2.2 genes play a key role in the regulation of the high-affinity NO 3 Ϫ uptake, and in the adaptative responses of the plant to both spatial and temporal changes in nitrogen availability in the environment. The uptake of NO 3Ϫ by roots cells is a key process for higher plants because it is the first step of the assimilatory pathway providing most of organic nitrogen required for synthesis of biomolecules, including proteins and nucleic acids (Beevers and Hageman, 1980). More than 30 years of physiological investigations have led to the conclusion that at least three uptake systems are responsible for the influx of NO 3 Ϫ into the roots (for review, see Clarkson, 1986;Glass and Siddiqi, 1995;Crawford and Glass, 1998;Daniel-Vedele et al., 1998;Forde, 2000). Two highaffinity transport systems (HATS) are able to take up NO 3 Ϫ at low concentrations in the external medium, and display saturable kinetics as a function of the external NO 3 Ϫ concentration ([NO 3 Ϫ ] o ), with saturation in the range of 0.2 to 0.5 mm [NO 3 Ϫ ] o . One of these systems appears to be present even in plants never supplied with NO 3 Ϫ , and thus is considered as constitutive (cHATS). The other HATS is specifically stimulated by NO 3 Ϫ , and is consequently assumed to be inducible (iHATS). The maximum activity (V max ) recorded for the iHATS is generally much larger than that of the cHATS, suggesting that the former system plays a key role in the root uptake of NO 3 Ϫ from external media where [NO 3 Ϫ ] o does not exceed 1 mm. The iHATS and cHATS appear to be genetically distinct because a mutant defective in the cHATS, but not in the iHATS, has been isolated in Arabidopsis (Wang and Crawford, 1996)....

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“…As a first example, nitrate itself induces nitrate transporters and NR, leading to higher rates of nitrate uptake and assimilation (Hoff, Truong & Caboche 1994;Crawford 1995;Scheible et al 1997a;Krapp et al 1997). The decreased concentration of total and organic nitrogen and decreased activity of NR in elevated [CO 2 ] (see above) might therefore be due to a depletion of nitrate in the soil and plant, rather than a fundamental inability to increase nitrate uptake and assimilation to match the increased rates of photosynthesis in elevated [CO 2 ].…”

Section: Introductionmentioning

confidence: 99%

The nitrate and ammonium nitrate supply have a major influence on the response of photosynthesis, carbon metabolism, nitrogen metabolism and growth to elevated carbon dioxide in tobacco

Geiger¹,

Haake²,

Ludewig³

et al. 1999

Plant Cell & Environment

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The nitrogen concentration usually decreases in elevated [CO 2 ] (Wong 1979;Hocking & Meyer 1985;Hocking & Meyer 1991a, 1991bColeman et al. 1993;Pettersson, MacDonald & Stadenburg 1993;Rogers et al. 1993;McKee & Woodward 1994;Jacob, Greitner & Drake 1995;Nie et al. 1995;Poorter et al. 1997), indicating that nitrogen uptake lags behind carbohydrate synthesis and growth in elevated [CO 2 ]. The effect of elevated [CO 2 ] on the nitrate uptake rates per unit root weight is rather variable and apparently depends on the nitrogen concentration supplied (Larigauderie, Reynolds & Strain 1994) and the species. Whereas elevated [CO 2 ] increased the rate of nitrate uptake per unit root weight in loblolly pines (Bassirirad et al. 1996) and Prosopis glandulosa (Bassirirad et al. 1997), it did not alter nitrate uptake in Nardus agrostis (Bassirirad et al. 1997), and it decreased nitrate uptake in a mixed field community (Jackson & Reynolds 1996). Although nitrate uptake might be improved in elevated [CO 2 ] because plants possess more roots and exploit a larger soil volume (see, e.g. Stulen & den Hertog 1993;Pettersson et al. 1993;Jackson & Reynolds 1996), the decreased water flow in elevated [CO 2 ] will tend to decrease the root surface concentrations of nitrate (Van Vuuren et al. 1997).The organic nitrogen concentration decreases in elevated [CO 2 ] (Wong 1979;Curtis, Drake & Whigham 1989;Garbutt, Williams & Bazzaz 1990;Coleman et al. 1991;Hocking & Meyer 1991a, 1991bColeman & Bazzaz 1992;Gries, Kimball & Idso 1993;Pettersson et al. 1993;Körner & Miglietta 1994;Pettersson & MacDonald 1994; FerrarioMery et al. 1997;Poorter et al. 1997), indicating that nitrate assimilation fails to keep pace with growth. There is conflicting evidence with respect to the effect of elevated [CO 2 ] on nitrate reductase (NR) activity. Although elevated [CO 2 ] led to a small increase of NR activity in mustard (Maeskaya et al. 1990) and Vigna radiata (Sharma & Sen Gupta 1990), it produced a two-fold decrease of NR activity in wheat (Hocking & Meyer 1991a), maize (Purvis, Peters & Hageman 1974), and a 15-25% decrease in Nicotiana plumbaginifolia (Ferrario-Mery et al. 1997). It also led to a decrease of nitrite reductase activity in lettuce (Besford & Hand 1989). In Plantago major, elevated [CO 2 ] led to a transient increase in NR activity, that was reversed after a few days (Fonseca, Bowsher & Stulen 1997). These reports of a decrease of NR activity in elevated [CO 2 ] are rather surprising, because exogenous sugars lead to increased expression of Nia (Cheng et al. 1992;Vincentz et al. 1993;Krapp et al. 1993;Krapp & Stitt 1995;Morcuende et al. 1998) and post-translational activation of NR (Kaiser & Huber 1994; Huber, Bachman & Huber 1996) in detached leaves. Recently Geiger et al. (1998) showed that although elevated [CO 2 ] does not markedly increase the maximum NR activity in tobacco the diurnal regulation of NR is modified, allowing higher activity in the later part of the light period and during the night.Even less is kno...

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Expression studies of Nrt2:1Np, a putative high‐affinity nitrate transporter: evidence for its role in nitrate uptake

Cited by 149 publications

References 46 publications

An Arabidopsis T‐DNA mutant affected in Nrt2 genes is impaired in nitrate uptake

An Arabidopsis T‐DNA mutant affected in Nrt2 genes is impaired in nitrate uptake

Major Alterations of the Regulation of Root NO3 − Uptake Are Associated with the Mutation of Nrt2.1 and Nrt2.2 Genes in Arabidopsis

The nitrate and ammonium nitrate supply have a major influence on the response of photosynthesis, carbon metabolism, nitrogen metabolism and growth to elevated carbon dioxide in tobacco

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