The Biochemistry, Molecular Biology, and Genetic Manipulation of Primary Ammonia Assimilation

Hirel, Bertrand; Lea, Peter J.

doi:10.1007/0-306-48138-3_6

Cited by 23 publications

(24 citation statements)

References 159 publications

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“…These data demonstrate that ammonia assimilation, which in source leaves is considered to be a largely chloroplastic function (Hirel and Lea, 2002), is affected by partitioning between different mitochondrial electron transport pathways. Indeed, it is striking that complex I deficiency affects the Gln:Glu and Asn:Asp ratios much more than the Gly:Ser ratio (Figs.…”

Section: Mitochondria-driven Effects On Nad Status Exert a Major Inflmentioning

confidence: 69%

“…Although the Arabidopsis (Arabidopsis thaliana) gene GLN2 has been found to encode a dual-targeted GS (Taira et al, 2004), most evidence suggests that net ammonia assimilation occurs mainly in the chloroplast, where ferredoxin-Glu synthase activity requires 2-OG (Hirel and Lea, 2002). Figure 10.…”

Section: Leaf Nad Status Is a Key Factor In Coordinating The Supply Omentioning

confidence: 99%

“…Hence, much attention has focused on the regulation of key enzymes involved in the core interaction between carbon and nitrogen metabolism ( Fig. 1; Kaiser and Huber, 1994;Coschigano et al, 1998;Hirel and Lea, 2002;Hodges, 2002;Stitt et al, 2002). Numerous studies have shown that carbon and nitrogen metabolites are monitored by the cell and act together to orchestrate gene expression, thus determining transcriptome profiles that are appropriate to nutritional and metabolic status (Wang et al, 2000;Palenchar et al, 2004).…”

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Mitochondria-Driven Changes in Leaf NAD Status Exert a Crucial Influence on the Control of Nitrate Assimilation and the Integration of Carbon and Nitrogen Metabolism

et al. 2005

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The Nicotiana sylvestris mutant, CMS, lacks the mitochondrial gene nad7 and functional complex I, and respires using lowaffinity NADH (alternative) mitochondrial dehydrogenases. Here, we show that this adjustment of respiratory pathways is associated with a profound modification of foliar carbon-nitrogen balance. CMS leaves are characterized by abundant amino acids compared to either wild-type plants or CMS in which complex I function has been restored by nuclear transformation with the nad7 cDNA. The metabolite profile of CMS leaves is enriched in amino acids with low carbon/nitrogen and depleted in starch and 2-oxoglutarate. Deficiency in 2-oxoglutarate occurred despite increased citrate and malate and higher capacity of key anaplerotic enzymes, notably the mitochondrial NAD-dependent isocitrate dehydrogenase. The accumulation of nitrogenrich amino acids was not accompanied by increased expression of enzymes involved in nitrogen assimilation. Partitioning of 15 N-nitrate into soluble amines was enhanced in CMS leaf discs compared to wild-type discs, especially in the dark. Analysis of pyridine nucleotides showed that both NAD and NADH were increased by 2-fold in CMS leaves. The growth retardation of CMS relative to the wild type was highly dependent on photoperiod, but at all photoperiod regimes the link between high contents of amino acids and NADH was observed. Together, the data provide strong evidence that (1) NADH availability is a critical factor in influencing the rate of nitrate assimilation and that (2) NAD status plays a crucial role in coordinating ammonia assimilation with the anaplerotic production of carbon skeletons.Nitrogen is often a limiting factor for plant growth and development. There is keen interest and considerable potential agronomic benefit in understanding the mechanisms that determine nitrogen use efficiency and in identifying targets for improvement. Hence, much attention has focused on the regulation of key enzymes involved in the core interaction between carbon and nitrogen metabolism ( Fig. 1; Kaiser and Huber, 1994;Coschigano et al., 1998;Hirel and Lea, 2002;Hodges, 2002;Stitt et al., 2002). Numerous studies have shown that carbon and nitrogen metabolites are monitored by the cell and act together to orchestrate gene expression, thus determining transcriptome profiles that are appropriate to nutritional and metabolic status (Wang et al., 2000;Palenchar et al., 2004). Other key controls occur posttranslationally via phosphorylation of proteins such as phosphoenolpyruvate carboxylase (PEPc) and nitrate reductase (NR; Van Quy et al., 1991;Kaiser and Huber, 1994), as well as by intricate regulation of enzyme activities by metabolite effectors (Moraes and Plaxton, 2000;Smith et al., 2000).As previously emphasized by ourselves and others, the carbon/nitrogen (C/N) interaction takes place within a context of energy use and production involving cooperation between different subcellular compartments (Foyer et al., 1994a(Foyer et al., , 2003Hoefnagel et al., 1998;Noctor and Foyer, 1998a;...

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Section: Mitochondria-driven Effects On Nad Status Exert a Major Inflmentioning

confidence: 69%

Section: Leaf Nad Status Is a Key Factor In Coordinating The Supply Omentioning

confidence: 99%

mentioning

confidence: 99%

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Mitochondria-Driven Changes in Leaf NAD Status Exert a Crucial Influence on the Control of Nitrate Assimilation and the Integration of Carbon and Nitrogen Metabolism

et al. 2005

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“…3) are in agreement with those obtained by Lasa et al (2002), which showed that GS activity increases in the presence of ammonium. The relative activities of GS isoenzymes in an organ or tissue appear to be tightly linked to specific roles of primary assimilation and co-ordination of C and N metabolism (Hirel and Lea 2002). In many of the plant species examined so far, ammonium does not have any effect on chloroplastic GS activity (Migge et al 2000).…”

Section: Discussionmentioning

confidence: 99%

“…In barley plants supplemented with ammonia, an increase in GS activity has also been observed (Ma¨ck 1995). It has been suggested that the cytolosic GS could work as an ammonium stress-adaptive mechanism, during which both GS gene expression and activity are induced (Terce´-Laforgue and Hirel 2000;Hirel and Lea 2002).…”

Section: Discussionmentioning

confidence: 99%

How does glutamine synthetase activity determine plant tolerance to ammonium?

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Domínguez-Valdivia

et al. 2005

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The wide range of plant responses to ammonium nutrition can be used to study the way ammonium interferes with plant metabolism and to assess some characteristics related with ammonium tolerance by plants. In this work we investigated the hypothesis of plant tolerance to ammonium being related with the plants' capacity to maintain high levels of inorganic nitrogen assimilation in the roots. Plants of several species (Spinacia oleracea L., Lycopersicon esculentum L., Lactuca sativa L., Pisum sativum L. and Lupinus albus L.) were grown in the presence of distinct concentrations (0.5, 1.5, 3 and 6 mM) of nitrate and ammonium. The relative contributions of the activity of the key enzymes glutamine synthetase (GS; under light and dark conditions) and glutamate dehydrogenase (GDH) were determined. The main plant organs of nitrogen assimilation (root or shoot) to plant tolerance to ammonium were assessed. The results show that only plants that are able to maintain high levels of GS activity in the dark (either in leaves or in roots) and high root GDH activities accumulate equal amounts of biomass independently of the nitrogen source available to the root medium and thus are ammonium tolerant. Plant species with high GS activities in the dark coincide with those displaying a high capacity for nitrogen metabolism in the roots. Therefore, the main location of nitrogen metabolism (shoots or roots) and the levels of GS activity in the dark are an important strategy for plant ammonium tolerance. The relative contribution of each of these parameters to species tolerance to ammonium is assessed. The efficient sequestration of ammonium in roots, presumably in the vacuoles, is considered as an additional mechanism contributing to plant tolerance to ammonium nutrition.

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