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  Steps towards an integrated view of nitrogen metabolism

Stitt, M., Mueller, C., Matt, P., Gibon, Y., Carillo, P., Morcuende, R., et al. (2002). Steps towards an integrated view of nitrogen metabolism. In 6th International Symposium on Inorganic Nitrogen Assimilation (pp. 959-970).

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0014-2E6E-5 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-0014-2E6F-3
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 Creators:
Stitt, M.1, Author              
Mueller, C.2, Author
Matt, P.2, Author
Gibon, Y.1, Author              
Carillo, P.2, Author
Morcuende, R.2, Author
Scheible, W.-R.3, Author              
Krapp, A.2, Author
Affiliations:
1System Regulation, Department Stitt, Max Planck Institute of Molecular Plant Physiology, Max Planck Society, ou_1753327              
2External Organizations, ou_persistent22              
3Molecular Genomics, Department Stitt, Max Planck Institute of Molecular Plant Physiology, Max Planck Society, ou_1753328              

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Free keywords: amino acids gogat malate nia nitrate reduction nitrogen metabolism ph nitrate reductase-activity amino-acid-metabolism higher-plants diurnal changes tobacco plants carbon-dioxide growth leaves assimilation expression
 Abstract: This article discusses how nitrate assimilation is integrated with nitrate uptake, with ammonium assimilation and amino acid synthesis, with pH regulation, and with the sugar supply in tobacco leaves. During the first part of the light period, nitrate assimilation exceeds nitrate uptake by 2-fold and ammonium assimilation by 50%, leading to rapid depletion of nitrate and accumulation of ammonium, glutamine, glycine and serine. NIA, Nil and PPC expression show a shared maximum early in the diurnal cycle to direct carbon towards malate synthesis for pH regulation. Later in the diurnal cycle an orchestrated increase of GLN2, PKc, CS, and ICDH-1 expression re-establishes a balance between nitrate assimilation and ammonium metabolism. Nitrate uptake continues throughout the night, replenishing the leaf nitrate pool. These diurnal changes are attenuated or abolished in mutants with low NIA activity, and modified in wild-type plants growing on different nitrogen sources or elevated [CO2]. Comparison across genotypes and conditions reveals that NIA transcript levels are always closely related to the balance between nitrate influx and assimilation, but are unrelated to changes of glutamine or 2-oxoglutarate. In a systematic search for other downstream regulators, a wide range of downstream metabolites was fed to detached leaves and glutamate, cysteine, asparagine, and malate identified as candidates. Low sugars totally inhibit nitrate assimilation, overriding signals from nitrogen metabolism. Moderate changes act post-transcriptionally, and larger changes lead to a collapse of the NIA transcript. Low sugars also lead to a collapse of minor amino acids and a dramatic decrease of phenylpropanoids and nicotine. Consequently, wildtype plants growing in unfavourable light regimes and antisense RBCS transformants are simultaneously carbon- and nitrogen-limited.

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Language(s): eng - English
 Dates: 2002
 Publication Status: Published in print
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 Identifiers: ISI: ISI:000174853500019
DOI: 10.1093/jexbot/53.370.959
URI: ://000174853500019 http://jxb.oxfordjournals.org/content/53/370/959.full.pdf
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Title: 6th International Symposium on Inorganic Nitrogen Assimilation
Place of Event: REIMS, FRANCE
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Title: 6th International Symposium on Inorganic Nitrogen Assimilation
Source Genre: Proceedings
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Pages: - Volume / Issue: - Sequence Number: - Start / End Page: 959 - 970 Identifier: -