Cereal grain, rachis and pulse seed amino acid δ15N values as indicators of plant nitrogen metabolism (original) (raw)
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The central role of amino acids on nitrogen utilization and plant growth
Journal of Plant Physiology, 1996
Plant nitrogen metabolism is regulated by nitrogen supply and by plant demand for growth. In recent years it has become evident that many of the processes and metabolic pathways of plant nitrogen metabolism are regulated by the concentration of all or several amino acids and amides. The role of amino acids and amides in the regulation of nitrate and ammonium uptake, nitrate reduction, ammonium incorporation, protein metabolism and N remobilization is discussed. It is proposed that as the free amino-acid concentrations are dependent on the plant N status, changes in their cytoplasmic concentration may be involved in the regulation of plant growth and N utpake.
Protoplasma, 2017
Sustainable development of cellular organisms depends on a precise coordination between the carbon and nitrogen metabolisms within the living system. Inorganic N is assimilated into amino acids which serve as an important N source for various regulatory metabolic pathways in plants. This study investigates the role of amino acids in C/N balance by examining changes in amino acid profile in the leaves and roots of low-N-tolerant (PHEM-2) and low-N-sensitive (HM-4) maize genotypes grown hydroponically under N-sufficient (4.5 mM), N-deficient (0.05 mM) and N-restoration conditions. N application effectively altered the level of cysteine, methionine, asparagine, arginine, phenylalanine, glycine, glutamine, aspartate and glutamate in both genotypes. Under low N (0.05 mM), the asparagine and glutamine contents increased, while those of glutamate, phenylalanine and aspartate decreased in both genotypes. However, serine content increased in PHEM-2 but decreased in HM-4. Resupply of N to low...
Plant, Soil and Environment, 2010
In two-year field experiments, nitrogen (N) in the form of urea (0, 120 and 240 kg N/ha) was applied to grain maize (Zea mays L.) hybrid KWS 2376. The two-year mean content of total grain N at harvest was 1.54%. The highest N dose reduced most of the 17 amino acids (AA) analysed in the grain compared with the other treatments. Possible reasons for this could be an adverse effect on the tricarboxylic acid cycle or deficiency of carbon skeletons for the assimilation of NH4+ into amides and amino acids. The content of the limiting amino acid lysine was not influenced by N fertilisation, with a mean two-year content of 2.02 mg/g DM. Taking into account the differences in fertilisation, the effect of the year was seen in the maximal accumulation of amino acids serine, proline, methionine, threonine, arginine and lysine. Increasing rates of nitrogen reduced the accumulation of asparagine and glycine, and, on the contrary, increased the accumulation of tyrosine. Nitrogen rates have a signi...
Co-ordination of leaf minor amino acid contents in crop species: significance and interpretation
Journal of Experimental Botany, 2002
The question of whether general control of amino acid synthesis exists in plants remains to be resolved. It is not known whether there is overall co-ordination of the biosynthesis of amino acids that are formed through distinct pathways. In this work, amino acid contents were measured in a large number of samples taken from wheat, potato and barley leaves under different photosynthetic conditions. The variability in total soluble amino acid contents between samples was approximately 6-fold in wheat and potato. Subtracting the major amino acids from the total soluble amino acids showed that the variability in summed minor amino acid contents was approximately 20-fold. This variability was not correlated with short-term changes in primary carbon and nitrogen metabolism, and only poorly correlated with total leaf amino acids. By contrast, striking linear relationships between the contents of most minor amino acids were observed, demonstrating that the contents of many minor amino acids vary in concert. These observations show that amino acid contents are co-ordinated across biosynthetic families. While these data might be interpreted as an indication of cross-pathway regulation of the expression of key biosynthetic enzymes, the impact of factors such as protein degradation and storage cannot be ignored.
Amino Acid Transport and Metabolism in Relation to the Nitrogen Economy of a Legume Leaf
PLANT PHYSIOLOGY, 1983
ABSTRACI Net balances of amino acids were constructed for stages of development of a leaf of white lupin (Lupinus abus L.) using data on the N economy of the leaf, its exchanges of amino acids through xylem and phloem, and net changes in its soluble and protein-bound amino acids. Asparagine, aspartate, and y-aminobutyrate were delivered to the leaf in excess of amounts consumed in growth and/or phloem export. Glutamine was supplied in excess until full leaf expansion (20 days) but was later synthesized in large amounts in association with mobilization of N from the leaf. Net requirements for glutamate, threonine, serine, proline, glycine, alanine, valine, isoleucine, leucine, tyrosine, phenylalanine, histidine, lysine, and arginine were met mainly or entirely by synthesis within the leaf. Amides furnished the bulk of the N for amino acid synthesis, asparagine providing from 24 to 68%. In vitro activity of asparaginase (EC 3.5.1.1) exceeded that of asparagine:pyruvate aminotransferase (EC 2.6.1.14) during early leaf expansion, when in vivo estimates of asparagine metabolism were highest. Thereafter, aminotransferase activity greatly exceeded that of asparaginase. Rates of activity of one or both asparagine-utilizing enzymes exceeded estimated rates of asparagine catabolism throughout leaf development. In vitro activities of glutamine synthetase (EC 6.3.1.2) and glutamate synthase (EC 1.4.7.1) were consistently much higher than that of glutamate dehydrogenase (EC 1.4.13), and activities of the former two enzymes more than accounted for estimated rates of ammonia release in photorespiration and deamidation of asparagine.
Current Protocols in Plant Biology, 2018
The human body contains approximately 3.2% nitrogen (N), mainly present as protein and amino acids. Although N exists at a high concentration (78%) in the air, it is not readily available to animals and most plants. Plants are however able to take up both nitrate (NO 3 −) and ammonium (NH 4 +) ions from the soil and convert them to amino acids and proteins, which are excellent sources for all animals. Most N is available as the stable isotope 14 N, but a second form, 15 N, is present in very low concentrations. 15 N can be detected in extracts of plants by gas chromatography followed by mass spectrometry (GC/MS). In this protocol, the methods are described for tracing the pathway by which plants are able to take up 15 N-labeled nitrate and ammonium and convert them into amino acids and proteins. A protocol for extracting and quantifying amino acids and 15 N enrichment in maize (Zea mays L.) leaves labeled with 15 NH 4 + is described. Following amino acid extraction, purification, and separation by GC/MS, a calculation of the 15 N enrichment of each amino acid is carried out on a relative basis to identify any differences in the dynamics of amino acid accumulation. This will allow a study of the impact of genetic modifications or mutations on key reactions involved in primary nitrogen and carbon metabolism.
2011
Hard red winter wheat seedlings (Triticum aestivum cv "Winoka") grown in sand were fertilized with a medium containing 15 NH 4 15 NO 3 as the sole source of N. The 15 N coupled with gas chromatography-mass spectrometry (GC-MS) was used to track amino acid synthesis. 15 N incorporation was determined for both the 1st and 2nd leaves harvested separately from each seedling. In well-watered (WW) conditions for the 1st leaf, the greatest percentage of 15 N incorporation was observed for Ile (61%), Gln (60%), Ser (57%), and Leu (55%) and in the 2nd leaf, the greatest 15 N incorporation was observed for Asn (66%), Ser (61%), and Ile (55%). There was a significant decline of 15 N incorporation between the 2nd and 1st leaf for Trp, Gln, and Met and a significant increase for Cys and Asn. Under drought-stressed conditions for the 1st leaf, there was a significant increase of 15 N incorporation for Trp and Tyr and a significant decline of 15 N incorporation for Gln, Lys, Met, Cys, and Phe. Similarly, under drought conditions for the 2nd leaf, 15 N incorporation was significantly decreased for Cys and Ala and there was a significant increase for Phe, Asp, Gly, Met, Gln, and Trp. We are now positioned to examine the incorporation of the 15 N amino acids into proteins and then to study protein turnover in response to drought.
The effect of manuring on cereal and pulse amino acid δ(15)N values
Phytochemistry, 2014
a b s t r a c t Amino acid d 15 N values of barley (Hordeum vulgare) and bread wheat (Triticum aestivum) grains and rachis and broad bean (Vicia faba) and pea (Pisum sativum) seeds, grown in manured and unmanured soil at the experimental farm stations of Rothamsted, UK and Bad Lauchstädt, Germany, were determined by GC-C-IRMS. Manuring was found to result in a consistent 15 N-enrichment of cereal grain amino acid d 15 N values, indicating that manuring did not affect the metabolic routing of nitrogen (N) into cereal grain amino acids. The increase in cereal grain d 15 N values with manuring is therefore due to a 15 N-enrichment in the d 15 N value of assimilated inorganic-N. Greater variation was observed in the 15 N-enrichment of rachis amino acids with manuring, possibly due to enhanced sensitivity to changes in growing conditions and higher turnover of N in rachis cells compared to cereal grains. Total amino acid d 15 N values of manured and unmanured broad beans and peas were very similar, indicating that the legumes assimilated N 2 from the atmosphere rather than N from the soil, since there was no evidence for routing of 15 N-enriched manure N into any of the pulse amino acids. Crop amino acid d 15 N values thus provide insights into the sources of N assimilated by non N 2 -fixing and N 2 -fixing crops grown on manured and unmanured soils, and reveal an effect of manure on N metabolism in different crop species and plant parts.
Zemdirbyste-Agriculture, 2015
University to determine the effect of different concentrations of amino acids on the dynamics of nitrogen, phosphorus and potassium in spring barley leaves and on grain productivity under the water deficit conditions. The following experimental design was used: factor A − different concentrations of amino acid solutions: the control (unsprayed), sprayed with water, sprayed with 0.5, 1.0, 1.5, 1.5 % with microelements and 2.0% amino acid solutions; factor B -time of fertilization with the amino acids: BBCH 21-23 and 26-29 growth stages. Topsoil moisture content decreased from 14.5% to 8.7% during the BBCH 21-49 stages and thus it was considered as water deficiency conditions. The amino acid solutions of different concentrations, used for spring barley fertilization under the water deficiency conditions during the BBCH 21-23 or 26-29 stages, significantly increased the nitrogen, phosphorus and potassium content in the plants during the BBCH 26-29 and 32-35 stages in comparison to the control plants that were not sprayed with water. In many cases, the water spray stimulated nitrogen uptake to the same extent as amino acids application. Having analysed the effect of spring barley fertilization with the amino acids, it was found that the content of nitrogen did not reach the optimal level in the leaves of plants. However, the content of phosphorus reached the minimal limit of the optimal content at the BBCH 26-29 stage. A significant yield increase (0.15-0.47 t ha -1 ) was obtained when the spring barley had been fertilized with the 1.0% concentration of amino acids solution during the BBCH 21-23 stage.
New Phytologist, 2006
In wheat the period of grain filling is characterized by a transition for all vegetative organs from sink to source status. • To study this transition, the progression of physiological markers and enzyme activities representative of nitrogen metabolism was monitored from the vegetative stage to maturity in different leaf stages and stem sections of two wheat ( Triticum aestivum ) cultivars grown at high and low levels of N fertilization. • In the two cultivars examined, we found a general decrease of the metabolic and enzyme markers occurred during leaf ageing, and that this decrease was enhanced when plants were N-limited. Both correlation studies and principal components analysis (PCA) showed that there was a strong relationship among total N, chlorophyll, soluble protein, ammonium, amino acids and glutamine synthetase (GS) activity.