Is nitrate reductase a major player in the plant NO (nitric oxide) game?

Meyer, Christian; Lea, Unni S.; Provan, Fiona; Kaiser, Werner M.; Lillo, Cathrine

doi:10.1007/s11120-004-3548-3

Cited by 123 publications

(86 citation statements)

References 56 publications

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“…Apparently, plants have various ways to assure that nitrate is not reduced in excess under conditions (e.g. in the dark) where toxic levels of nitrite or side products of the NR reaction might accumulate due to reduced metabolism of nitrite (Meyer et al, 2005). At 1 mM external nitrate, the uptake rate was apparently balanced with the assimilation rate, and S521D then reduced almost all the nitrate in the leaves.…”

Section: Discussionmentioning

confidence: 99%

Posttranslational Regulation of Nitrate Reductase Strongly Affects the Levels of Free Amino Acids and Nitrate, whereas Transcriptional Regulation Has Only Minor Influence

et al. 2006

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Diurnal variations in nitrate reductase (NR) activity and nitrogen metabolites were examined in wild-type Nicotiana plumbaginifolia and transformants with various degrees of NR deregulation. In the C1 line, NR was only deregulated at the transcriptional level by placing the NR gene under the control of the cauliflower mosaic virus 35S RNA promoter. In the Del8 and S521D lines, NR was additionally deregulated at the posttranslational level either by a deletion mutation in the N-terminal domain or by a mutation of the regulatory phosphorylation site (serine-521). Posttranslational regulation was essential for pronounced diurnal variations in NR activity. Low nitrate content was related to deregulation of NR, whereas the level of total free amino acids was much higher in plants with fully deregulated NR. Abolishing transcriptional and posttranslational regulation (S521D plants) resulted in an increase of glutamine and asparagine by a factor of 9 and 14, respectively, compared with wild type, whereas abolishing transcriptional regulation (C1 plants) only resulted in increases of glutamine and asparagine by factors ,2. Among the minor amino acids, isoleucine and threonine, in particular, showed enhanced levels in S521D. Nitrate uptake rates were the same in S521D and wild type as determined with 15 N feeding. Deregulation of NR appears to set the level of certain amino acids, whereas diurnal variations were still determined by light/dark. Generally, deregulation of NR at the transcriptional level did not have much influence on metabolite levels, but additional deregulation at the posttranslational level resulted in profound changes of nitrogen metabolite levels.

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Section: Discussionmentioning

confidence: 99%

Posttranslational Regulation of Nitrate Reductase Strongly Affects the Levels of Free Amino Acids and Nitrate, whereas Transcriptional Regulation Has Only Minor Influence

et al. 2006

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“…In contrast, NiR-deficient plants, which accumulate high nitrite levels, display chlorosis and dramatically reduced growth in tobacco (Nicotiana tabacum; Vaucheret et al, 1992) and rapid death in barley (Hordeum vulgare; Duncanson et al, 1993) if grown with nitrate. Such plants also produce high levels of nitric oxide (NO; Morot- Gaudry-Talarmain et al, 2002) because nitrite serves as a substrate for the formation of NO (Yamasaki et al, 1999;Rockel et al, 2002;Lea et al, 2004;Meyer et al, 2005;Planchet et al, 2005). It should be noted that nitrite can have a beneficial effect because it protects maize (Zea mays) roots from anoxia by reducing cytoplasmic acidosis (Libourel et al, 2006).…”

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confidence: 99%

Nitrite Acts as a Transcriptome Signal at Micromolar Concentrations in Arabidopsis Roots

2007

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Nitrate serves as a potent signal to control gene expression in plants and algae, but little is known about the signaling role of nitrite, the direct product of nitrate reduction. Analysis of several nitrate-induced genes showed that nitrite increases mRNA levels as rapidly as nitrate in nitrogen-starved Arabidopsis (Arabidopsis thaliana) roots. Both nitrite and nitrate induction are apparent at concentrations as low as 100 nM. The response at low nitrite concentrations was not due to contaminating nitrate, which was present at ,1% of the nitrite concentration. High levels of ammonium (20 mM) in the growth medium suppressed induction of several genes by nitrate, but had varied effects on the nitrite response. Transcriptome analysis using 250 or 5 mM nitrate or nitrite showed that over one-half of the nitrate-induced genes, which included genes involved in nitrate and ammonium assimilation, energy production, and carbon and nitrogen metabolism responded equivalently to nitrite; however, the nitrite response was more robust and there were many genes that responded specifically to nitrite. Thus, nitrite can serve as a signal as well as if not better than nitrate.

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“…The excess NO, which can be emitted via the stomata, may come from the reaction between NaR and nitrite. Meyer et al (2005) suggested that essential plant functions such as stomatal control would probably not be regulated by a reaction this uncertain: NaR strongly prefers NO 3 -over NO 2 -and moreover, not all plant leaves contain NO 2 -, since in some species and under some conditions NO 3 -is already assimilated in the roots. Hence, Meyer et al speculated that the NO produced by NaR is only an unnecessary side product.…”

Section: No Y Emissionmentioning

confidence: 99%

UV-induced NO<sub>y</sub> emissions in gas-exchange chambers enclosing Scots pine shoots: an analysis on their origin and significance

Raivonen¹

2008

Diss. For.

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3 Raivonen, M. 2008. UV-induced NO y emissions in gas-exchange chambers enclosing Scots pine shoots: an analysis on their origin and significance. Dissertationes Forestales 71. 50 p. Available at http://www.metla.fi/dissertationes/df71.htm ABSTRACTIt is essential to have a thorough understanding of the sources and sinks of oxidized nitrogen (NO y ) in the atmosphere, since it has a strong influence on the tropospheric chemistry and the eutrophication of ecosystems. One unknown component in the balance of gaseous oxidized nitrogen is vegetation. Plants absorb nitrogenous species from the air via the stomata, but it is not clear whether plants can also emit them at low ambient concentrations. The possible emissions are small and difficult to measure.The aim of this thesis was to analyse an observation made in southern Finland at the SMEAR II station: solar ultraviolet radiation (UV) induced NO y emissions in chambers measuring the gas exchange of Scots pine (Pinus sylvestris L.) shoots. Both measuring and modelling approaches were used in the study. The measurements were performed under noncontrolled field conditions at low ambient NO y concentrations.The chamber blank i.e. artefact NO y emissions from the chamber walls, was dependent on the UV irradiance and increased with time after renewing the Teflon film on chamber surfaces. The contribution of each pine shoot to the total NO y emissions in the chambers was determined by testing whether the emissions decrease when the shoots are removed from their chambers. Emissions did decrease, but only when the chamber interior was exposed to UV radiation. It was concluded that also the pine shoots emit NO y . The possible effects of transpiration on the chamber blank are discussed in the summary part of the thesis, based on previously unpublished data.The possible processes underlying the UV-induced NO y emissions were reviewed. Surface reactions were more likely than metabolic processes. Photolysis of nitrate deposited on the needles may have generated the NO y emissions; the measurements supported this hypothesis. In that case, the emissions apparently would consist mainly of nitrogen dioxide (NO 2 ), nitric oxide (NO) and nitrous acid (HONO). Within studies on NO y exchange of plants, the gases most frequently studied are NO 2 and NO (=NO x ). In the present work, the implications of the emissions for the NO x exchange of pine were analysed with a model including both NO y emissions and NO y absorption. The model suggested that if the emissions exist, pines can act as an NO x source rather than a sink, even under relatively high ambient concentrations.

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Is nitrate reductase a major player in the plant NO (nitric oxide) game?

Cited by 123 publications

References 56 publications

Posttranslational Regulation of Nitrate Reductase Strongly Affects the Levels of Free Amino Acids and Nitrate, whereas Transcriptional Regulation Has Only Minor Influence

Posttranslational Regulation of Nitrate Reductase Strongly Affects the Levels of Free Amino Acids and Nitrate, whereas Transcriptional Regulation Has Only Minor Influence

Nitrite Acts as a Transcriptome Signal at Micromolar Concentrations in Arabidopsis Roots

UV-induced NO<sub>y</sub> emissions in gas-exchange chambers enclosing Scots pine shoots: an analysis on their origin and significance

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