<sup>15</sup>N NUCLEAR MAGNETIC RESONANCE STUDY OF AMMONIUM ION ASSIMILATION BY <i>LEMNA GIBBA</i> L.

Monselise, Edna Ben-Izhak; Kost, Daniel; Porath, Dan; Tal, Moshe

doi:10.1111/j.1469-8137.1987.tb00186.x

Cited by 16 publications

(12 citation statements)

References 15 publications

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“…As demonstrated by a number ofstudies on bacterial, fungal (12,13,16) and plant (9,17,19,22) As we have observed in the short term perfusion experiments with P. glauca buds, ammonia first enters the Gln amine pool and subsequently appears in the Glu aNH2 group (Figs. 5 and 6).…”

Section: Discussionmentioning

confidence: 89%

“…It is possible to use both '4N and '5N in noninvasive high resolution NMR studies (1,(11)(12)(13)(14)(15)(16)(17). Although solid state 'sN NMR has been used quite extensively (see [3] and references therein), only few high resolution studies utilizing '4N (1, 13) and '5N NMR (17,19) probing metabolism in plants have been reported. As we will show here, the study of both nuclei can provide useful information that is often complimentary.…”

mentioning

confidence: 99%

“…Moreover, it has the advantage that potentially one can follow metabolism in the same specimen and can be in a better position to correlate physiological findings with subsequent behavior (14,22,27). It is possible to use both '4N and '5N in noninvasive high resolution NMR studies (1,(11)(12)(13)(14)(15)(16)(17). Although solid state 'sN NMR has been used quite extensively (see [3] and references therein), only few high resolution studies utilizing '4N (1, 13) and '5N NMR (17,19) probing metabolism in plants have been reported.…”

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confidence: 99%

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A ¹⁴N and ¹⁵N Nuclear Magnetic Resonance Study of Nitrogen Metabolism in Shoot-Forming Cultures of White Spruce (Picea glauca) Buds

Thorpe

Bagh²,

Cutler³

et al. 1989

Plant Physiol.

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Nitrogen-14 and nitrogen-15 nuclear magnetic resonance (NMR) spectra were recorded for freshly dissected buds of Picea glauca and for buds grown for 3, 6 and 9 weeks on shoot-forming medium. Resonances for Glu (and other aNH2 groups), Pro, Ala, and the side chain groups in Gin, Arg, Om, and 'y-aminobutyric acid could be detected in in vivo 15N NMR spectra. Peaks for aamino groups, Pro, N03-and NH4 could also be identified in 14N NMR spectra. Perfusion experiments performed for up to 20 hours in the NMR spectrometer showed that 15N-labeled NH4 and N03-are first incorporated into the amide group of Gin and then in the aNH2 pool. Subsequently, it also emerges in Ala and Arg. These data suggest that the glutamine synthetase/ glutamate synthase pathway functions under these conditions. The assimilation of NH4+ is much faster than that of N03-. Consequently after 10 days of growth more than 70% of the newly synthesized intemal free amino acid pool derives its nitrogen from NH4+ rather than N03-. If NH4+ is omitted from the medium, no N03-is taken up during 9 weeks and the buds support limited growth by utilizing their endogenous amino acid pools. It is concluded that NH4 and N03-are both required for the induction of nitrate-and nitrite reductase.The use of tissue culture technology in the micropropagation of plants is the widest application of this technology to date (5, 26). The process of de novo organ formation in tissue cultures can be manipulated by the judicious choice of the explant, medium and culture environment. The medium manipulation includes the selection of a proper mineral salt formulation, a key component of which is the concentration of inorganic nitrogen and the ratio of NO3-to NH4' (9). Differences in nitrogen assimilation and amino acid metabolism may lead to a change in the content and spectrum of amino acids and both structural and enzymatic proteins in

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Section: Discussionmentioning

confidence: 89%

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confidence: 99%

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A ¹⁴N and ¹⁵N Nuclear Magnetic Resonance Study of Nitrogen Metabolism in Shoot-Forming Cultures of White Spruce (Picea glauca) Buds

Thorpe

Bagh²,

Cutler³

et al. 1989

Plant Physiol.

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“…The mass range scanned was 50 -650 atomic mass units for electron ionization studies. The specific isotopic abundance of Phe, Gln, and Glu was determined by plotting extracted ion current profiles and calculating ratios from the following ion clusters: Phe ( 18 O, 29 Si, and 30 Si as follows (34). Si 2 )} I 431 SCHEME 1.…”

Section: Nhmentioning

confidence: 99%

Nitrogen Metabolism in Lignifying Pinus taeda Cell Cultures

Heerden¹,

Towers²,

Lewis

1996

Journal of Biological Chemistry

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The primary metabolic fate of phenylalanine, following its deamination in plants, is conscription of its carbon skeleton for lignin, suberin, flavonoid, and related metabolite formation. Since this accounts for ϳ30 -40% of all organic carbon, an effective means of recycling the liberated ammonium ion must be operative. In order to establish how this occurs, the uptake and metabolism of various N NMR, and gas chromatography-mass spectrometry analyses. It was found that the ammonium ion released during active phenylpropanoid metabolism was not made available for general amino acid/protein synthesis. Rather it was rapidly recycled back to regenerate phenylalanine, thereby providing an effective means of maintaining active phenylpropanoid metabolism with no additional nitrogen requirement. These results strongly suggest that, in lignifying cells, ammonium ion reassimilation is tightly compartmentalized.The successful colonization of land by vascular plants, from their aquatic forerunners, was in large measure due to elaboration of the phenylpropanoid/phenylpropanoid-acetate pathways. At this critical juncture in evolution, phenylalanine (tyrosine) became the portal entry of phenols into lignins, lignans, flavonoids, suberins, and proanthocyanidins. Vascular plants thus have a very high Phe/Tyr turnover, since ϳ30 -40% of all assimilated carbon in photosynthesis is of phenylpropanoid/ phenylpropanoid-acetate origin (1-5).Phenylpropanoid metabolism is not only a feature of normal development, but can also be induced. For example, when loblolly pine (Pinus taeda) cell suspension cultures are exposed to high levels of sucrose (6), there is an induction of lignin synthesis. Curiously, little attention has been paid to the issue of the relationship between phenylpropanoid and nitrogen metabolism (7). This is surprising since there are many indications from physiological studies of significant metabolic relations between nitrogen depletion and the build-up of aromatic compounds, e.g. Lotus pendunculatus produces flavolans under nitrogen-limiting conditions, but not when nitrogen is provided (8).Scrutiny of the prearomatic pathway, leading to Phe/Tyr, and subsequent phenylpropanoid/phenylpropanoid-acetate metabolism reveals some noteworthy features. First, prephenate accepts an amino group from glutamate via transamination, constituting the point whereby nitrogen is introduced (9 -15). Second, when Phe/Tyr are committed to phenylpropanoid metabolism, rather than to protein or alkaloid synthesis, nitrogen (as the ammonium ion) is immediately removed via the appropriate lyase reaction (16 -18) (Scheme 1). Third, for every mole of cinnamate (p-hydroxycinnamate) formed, an equimolar amount of ammonium ion is generated. Consequently, an efficient means of nitrogen recycling must exist within cells undergoing active phenylpropanoid metabolism, otherwise severe nitrogen deficiency would result. A possible mechanism for recycling is shown in Scheme 2, where the ammonium ion released during lysis is metabolized via glutamine synthet...

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“…The first observations of intracellular 15N-amino acids in higher plants using 15N-NMR spectroscopy have been published only recently (Neeman et al 1985;Monselise et al 1987; Thorpe et al 1989;Robinson et al 1991;Amancio and Santos 1992). In this paper we report on a comparative study of NH2 uptake by two duckweeds (Lemnaceae): Wolffia arrhiza (L.) Hork.…”

Section: Introductionmentioning

confidence: 99%

Different ammonium-ion uptake, metabolism and detoxification efficiencies in two Lemnaceae

Monselise

Kost

1993

Planta

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lSN.Nuclea r magnetic resonance spectroscopy was used to follow nitrogen assimilation and amino-acid production in Wolffia arrhiza (L.) Hork. ex. Wimmer, clone Golan exposed to 4.0 mM 15NH4C1 solutions for 24 h. The main 15N_labelled metabolites were asparagine and glutamine, as well as substantial amounts of unreacted, intracellular NH~. These results were compared with those of a previous study on Lemna 9ibba L. clone Hurfeish (Monselise et al., 1987, New Phytol. 10, 341-345) with regard to NH2 uptake, assimilation and detoxification efficiencies. Both species, grown under continuous white light, were capable of preferential uptake of NH2 in the presence of nitrate. Relative growth rates indicate that both species tolerate increased levels of NH +, up to 10 -2 mol" 1-1, with L. 9ibba showing a slightly greater tolerance. No 15N-labelled free NH2 was detectable in L. 9ibba, while in W. arrhiza excess NH2 was found within the cells. This fact indicates that L. 9ib -ba is more efficient in detoxification than W. arrhiza, presumably because of inability of W. arrhiza to regenerate the "NH + traps", glutamate and aspartate, rapidly enough. This is also evident from the observation that addition of a-ketoglutarate to the medium caused nearly complete assimilation of intracellular NH + in W. arrhiza. In both plants, addition of a-ketoglutarate increased both NH2 uptake and assimilation. Addition of L-methionine DL-sulfoximine, an inhibitor of glutamine synthetase inhibited NH + assimilation, while addition of azaserine, an inhibitor of glutamate synthase, resulted in 15N incorporation into the glutamine-amide position only. These results are consistent with the glutamine synthetase-glutamate synthase pathway being the * This article is dedicated to Professor Bernhard Schrader on the occasion of his 60th birthday Abbreviations: AZA = azaserine (O-diazoacetyl-L-serine) ; GOGAT=glutamine oxoglutarate amine transferase=glutamate synthase E.C. 1.4.7. and E.C. 1.4.1.13. ; GS = glutamine synthetase E.C. 6.3.1.2. ; a-KG = c~-ketoglutarate = 2-oxoglutarate; MSO = Lmethionine DL-sulphoximine; NMR -nuclear magnetic resonance; RGR = relative growth rate major route of NH2 assimilation in the two plants under the conditions used.

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¹⁵N NUCLEAR MAGNETIC RESONANCE STUDY OF AMMONIUM ION ASSIMILATION BY LEMNA GIBBA L.

Cited by 16 publications

References 15 publications

A ¹⁴N and ¹⁵N Nuclear Magnetic Resonance Study of Nitrogen Metabolism in Shoot-Forming Cultures of White Spruce (Picea glauca) Buds

A ¹⁴N and ¹⁵N Nuclear Magnetic Resonance Study of Nitrogen Metabolism in Shoot-Forming Cultures of White Spruce (Picea glauca) Buds

Nitrogen Metabolism in Lignifying Pinus taeda Cell Cultures

Different ammonium-ion uptake, metabolism and detoxification efficiencies in two Lemnaceae

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15N NUCLEAR MAGNETIC RESONANCE STUDY OF AMMONIUM ION ASSIMILATION BY LEMNA GIBBA L.

Cited by 16 publications

References 15 publications

A 14N and 15N Nuclear Magnetic Resonance Study of Nitrogen Metabolism in Shoot-Forming Cultures of White Spruce (Picea glauca) Buds

A 14N and 15N Nuclear Magnetic Resonance Study of Nitrogen Metabolism in Shoot-Forming Cultures of White Spruce (Picea glauca) Buds

Nitrogen Metabolism in Lignifying Pinus taeda Cell Cultures

Different ammonium-ion uptake, metabolism and detoxification efficiencies in two Lemnaceae

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¹⁵N NUCLEAR MAGNETIC RESONANCE STUDY OF AMMONIUM ION ASSIMILATION BY LEMNA GIBBA L.

A ¹⁴N and ¹⁵N Nuclear Magnetic Resonance Study of Nitrogen Metabolism in Shoot-Forming Cultures of White Spruce (Picea glauca) Buds

A ¹⁴N and ¹⁵N Nuclear Magnetic Resonance Study of Nitrogen Metabolism in Shoot-Forming Cultures of White Spruce (Picea glauca) Buds