scholarly journals Nitrogen Regulating the Expression and Localization of Four Glutamine Synthetase Isoforms in Wheat (Triticum aestivum L.)

2020 ◽  
Vol 21 (17) ◽  
pp. 6299
Author(s):  
Yihao Wei ◽  
Xiaochun Wang ◽  
Zhiyong Zhang ◽  
Shuping Xiong ◽  
Xiaodan Meng ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Assimilation ◽  
Vascular Tissue ◽  
Mrna Level ◽  
Triticum Aestivum L ◽  
Kinetic Properties ◽  
High Catalytic Activity ◽  
Root Tips ◽  
Plant Nitrogen ◽  
Key Enzyme

Glutamine synthetase (GS), the key enzyme in plant nitrogen assimilation, is strictly regulated at multiple levels, but the most relevant reports focus on the mRNA level. Using specific antibodies as probes, the effects of nitrogen on the expression and localization of individual wheat GS (TaGS) isoforms were studied. In addition to TaGS2, TaGS1;1 with high affinity to substrate and TaGS1;3 with high catalytic activity were also localized in mesophyll, and may participate in cytoplasmic assimilation of ammonium (NH4+) released from photorespiration or absorbed by roots; TaGS1;2 was localized in xylem of leaves. In roots, although there were hundreds of times more TaGS1;1 than TaGS1;2 transcripts, the amount of TaGS1;1 subunit was not higher than that of TaGS1;2; NH4+ inhibited TaGS1;1 expression but stimulated TaGS1;3 expression. In root tips, nitrate stimulated TaGS1;1, TaGS1;3, and TaGS2 expression in meristem, while NH4+ promoted tissue differentiation and TaGS1;2 expression in endodermis and vascular tissue. Only TaGS1;2 was located in vascular tissue of leaves and roots, and was activated by glutamine, suggesting a role in nitrogen transport. TaGS1;3 was induced by NH4+ in root endodermis and mesophyll, suggesting a function in relieving NH4+ toxicity. Thus, TaGS isoforms play distinct roles in nitrogen assimilation for their different kinetic properties, tissue locations, and response to nitrogen regimes.

scholarly journals A New Perspective on the Role of Glutamine Synthetase in Nitrogen Remobilization in Wheat (Triticum aestivum L.)

2021 ◽  
Vol 22 (20) ◽  
pp. 11083
Author(s):  
Yihao Wei ◽  
Lulu Wang ◽  
Butan Qin ◽  
Huiqiang Li ◽  
Xiaoran Wang ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Vascular System ◽  
Grain Filling ◽  
Triticum Aestivum L ◽  
Nitrogen Remobilization ◽  
Plant Nitrogen ◽  
Key Enzyme ◽  
N Remobilization ◽  
New Perspective ◽  
Ureide Degradation

Glutamine synthetase (GS), a key enzyme in plant nitrogen metabolism, is closely related to nitrogen remobilization. However, how GS isoforms participate in nitrogen remobilization remains unclear. Here, the spatiotemporal expression of the TaGS gene family after anthesis was investigated, and the results showed that TaGS1;1 was mainly encoded by TaGS1;1-6A, while the other isozymes were mainly encoded by TaGS localized on the A and D subgenomes. TaGS1;2-4A/4D had the highest expression level, especially in rachis and peduncle. Furthermore, immunofluorescence showed TaGS1;2 was located in the phloem of rachis and peduncle. GUS (β-glucuronidase) staining confirmed that ProTaGS1;2-4A/4D::GUS activity was mainly present in the vascular system of leaves, roots, and petal of Arabidopsis. Ureides, an important transport form of nitrogen, were mainly synthesized in flag leaves and transported to grains through the phloem of peduncle and rachis during grain filling. TaAAH, which encodes the enzyme that degrades ureides to release NH4+, had a higher expression in rachis and peduncle and was synchronized with the increase in NH4+ concentration in phloem, indicating that NH4+ in phloem is from ureide degradation. Taking the above into account, TaGS1;2, which is highly expressed in the phloem of peduncle and rachis, may participate in N remobilization by assimilating NH4+ released from ureide degradation.

Studies on possible routes of ammonium assimilation in soybean root nodule bacteroids

1973 ◽  
Vol 19 (12) ◽  
pp. 1493-1499 ◽  
Author(s):  
Stanley D. Dunn ◽  
Robert V. Klucas
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Assimilation ◽  
Reductive Amination ◽  
Root Nodule ◽  
Root Nodules ◽  
Ammonium Assimilation ◽  
Kinetic Properties ◽  
Transferase Activity ◽  
Soybean Root

Glutamine amide–2-oxoglutarate aminotransferase NAD+ oxidoreductase (GOGAT), glutamine synthetase (GS), glutamate dehydrogenase (GD), and alanine dehydrogenase (AD) were studied in soybean root nodules. GS, GOGAT, and AD were present in bacteroids at levels that could account for ammonium assimilation, but GD activity was quite low. The total activities of GS and GD were higher in the cytosol than in the bacteroids by factors of 20 and 7, respectively, whereas GOGAT was not detected in the cytosol. GS (transferase activity) was inhibited by alanine, CTP, glycine, and tryptophan at 5 mM but was relatively unaffected by asparagine, aspartic acid, CMP, glucosamine, and histidine at 5 mM. GOGAT activity was unaffected by ATP, ADP, 8-hydroxyquinoline, and 1,10-phenanthroline but was inhibited by EDTA, citrate, and parachloromercuribenzoate. GOGAT activity (reductive amination) was also inhibited 97% by preincubation with 10−4 M azaserine for 30 min but GD activity was inhibited only 13%. The apparent Km values for NH4+ by AD was 7.4 × 10−3 M and by GD was 7.3 × 10−2 M while for glutamine by GOGAT it was 9.3 × 10−5 M. Activities and kinetic properties for these enzymes may suggest potential routes of nitrogen assimilation in vivo.

scholarly journals Elucidation of the role of glutamine synthetase seed isoform GLN1;5 in Arabidopsis thaliana (L.) with a reverse genetics approach

2019 ◽  
Vol 71 (3) ◽  
pp. 443-453
Author(s):  
Milan Dragicevic ◽  
Katarina Cukovic ◽  
Snezana Zdravkovic-Korac ◽  
Ana Simonovic ◽  
Milica Bogdanovic ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Glutamine Synthetase ◽  
Reverse Genetics ◽  
Technological Development ◽  
Expression Patterns ◽  
Dry Weight ◽  
Grain Filling ◽  
Kinetic Properties ◽  
Plant Nitrogen

Glutamine synthetase (E.C. 6.3.1.2) is a key enzyme of plant nitrogen metabolism that assimilates ammonia into glutamine. The Arabidopsis thaliana genome encodes one chloroplastic (GLN2) and five cytosolic (GLN1;1 ? GLN1;5) isoforms with different expression patterns, kinetic properties, regulation and functions. Physiological roles of different isoforms have been elucidated mainly by studying knockout mutants. However, the role of GLN1;5, which is expressed in dry seeds, remains unknown. To clarifty the function of GLN1;5, we studied a GLN1;5 knockout line (GLN1;5KO) homozygous for T-DNA insertion within the GLN1;5. GLN1;5 deficiency results in a phenotype with slightly delayed bolting and fewer siliques. The dry weight of GLN1;5KO seeds was 73.3% of wild-type (WT) seed weight, with seed length 90.9% of WT seeds. Finally, only 18.33% of the mutant seeds germinated in water within 10 days in comparison to 34.67% of WT seeds. KNO3 strongly stimulated germination of both GLN1;5KO and WT seeds, while germination in the presence of increasing NH4Cl concentrations potentiated the differences between the two genotypes. It can be concluded that GLN1;5 activity supports silique development and grain filling and that it has a role in ammonium reassimilation in the seed, as well as assimilation and/or detoxification of ammonium from the environment. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. ON173024 and Grant no. ON173015]

scholarly journals How do three cytosolic glutamine synthetase isozymes of wheat perform N assimilation and translocation?

2019 ◽  
Author(s):  
Yihao Wei ◽  
Xiaochun Wang ◽  
Zhiyong Zhang ◽  
Shuping Xiong ◽  
Yiming Zhang ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Assimilation ◽  
Root Tip ◽  
Kinetic Properties ◽  
Meristematic Zone ◽  
Ammonium Toxicity ◽  
Vascular Tissues ◽  
High Affinity ◽  
N Assimilation ◽  
Cytosolic Glutamine Synthetase

AbstractTo understand how the three cytosolic glutamine synthetase (GS1) isozymes of wheat (Triticum aestivum L., TaGS1) perform nitrogen assimilation and translocation, we studied the kinetic properties of TaGS1 isozymes, the effects of nitrogen on the expression and localization of TaGS1 isozymes with specific antibodies, and the nitrogen metabolism. The results showed TaGS1;1, the dominant TaGS1 isozyme, had a high affinity for substrates, and was widely localized in the mesophyll cells, root pericycle and root tip meristematic zone, suggesting it was the primary isozyme for N assimilation. TaGS1;2, with a high affinity for Glu, was activated by Gln, and was mainly localized in the around vascular tissues, indicating that TaGS1;2 catalyzed Gln synthesis in low Glu concentration, then the Gln returned to activate TaGS1;2, which may lead to the rapid accumulation of Gln around the vascular tissues. TaGS1;3 had low affinity for substrates but the highest Vmax among TaGS1, was mainly localized in the root tip meristematic zone; exogenous NH4+ could promote TaGS1;3 expressing, indicating that TaGS1;3 could rapidly assimilate NH4+ to relieve NH4+ toxicity. In conclusion, TaGS1;1, TaGS1;2 and TaGS1;3 have different role in N assimilation, Gln translocation and relieving ammonium toxicity, respectively, and synergistically perform nitrogen assimilation and translocation.HighlightThree cytosolic glutamine synthase isozymes of wheat have different role and synergistically perform nitrogen assimilation and translocation.

Glutamine Synthetase ( GS ): A Key Enzyme for Nitrogen Assimilation in The Macroalga Gracilariopsis lemaneiformis (Rhodophyta)

2019 ◽  
Vol 55 (5) ◽  
pp. 1059-1070 ◽  
Author(s):  
Xiaojuan Liu ◽  
Zhongyan Huan ◽  
Qingfang Zhang ◽  
Mingqi Zhong ◽  
Weizhou Chen ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Assimilation ◽  
Gracilariopsis Lemaneiformis ◽  
Key Enzyme

Elemental Analysis of Phloem Tissue in Lemna Minor Root Tips

1980 ◽  
Vol 38 ◽  
pp. 798-799
Author(s):  
Patrick Echlin ◽  
Thomas Hayes ◽  
Clifford Lai ◽  
Greg Hook
Keyword(s):  
Vascular Tissue ◽  
Lemna Minor ◽  
Atomic Weight ◽  
Companion Cell ◽  
Root Tips ◽  
Phloem Tissue ◽  
Cell Stage ◽  
Phloem Parenchyma ◽  
Parenchyma Cells ◽  
Xylem Element

Studies (1—4) have shown that it is possible to distinguish different stages of phloem tissue differentiation in the developing roots of Lemna minor by examination in the transmission, scanning, and optical microscopes. A disorganized meristem, immediately behind the root-cap, gives rise to the vascular tissue, which consists of single central xylem element surrounded by a ring of phloem parenchyma cells. This ring of cells is first seen at the 4-5 cell stage, but increases to as many as 11 cells by repeated radial anticlinal divisions. At some point, usually at or shortly after the 8 cell stage, two phloem parenchyma cells located opposite each other on the ring of cells, undergo an unsynchronized, periclinal division to give rise to the sieve element and companion cell. Because of the limited number of cells involved, this developmental sequence offers a relatively simple system in which some of the factors underlying cell division and differentiation may be investigated, including the distribution of diffusible low atomic weight elements within individual cells of the phloem tissue.

scholarly journals Chromatid and chromosome type breakage-fusion-bridge cycles in wheat (Triticum aestivum L.).

Genetics ◽  
1995 ◽  
Vol 140 (3) ◽  
pp. 1069-1085 ◽  
Author(s):  
A J Lukaszewski
Keyword(s):  
Triticum Aestivum ◽  
Ring Chromosome ◽  
Triticum Aestivum L ◽  
Aleurone Layer ◽  
Meiotic Pairing ◽  
Chromosome Type ◽  
Root Tips ◽  
Morphological Marker ◽  
Bfb Cycle ◽  
Tandem Duplications

Abstract During the development of disomic additions of rye (Secale cereale L.) chromosomes to wheat (Triticum aestivum L.), two reverse tandem duplications on wheat chromosomes 3D and 4A were isolated. By virtue of their meiotic pairing, the reverse tandem duplications initiated the chromatid type of the breakage-fusion-bridge (BFB) cycle. This BFB cycle continued through pollen mitoses and in the early endosperm divisions, but no clear evidence of its presence in embryo mitoses was found. The chromosome type of BFB cycle was initiated by fusion of two broken chromosome ends resulting in a dicentric or a ring chromosome. Chromosome type BFB cycles were detected in embryo mitoses and in root tips, but they did not persist until the next meiosis and were not transmitted to the progeny. Active BFB cycles induced breakage of other wheat chromosomes that resulted in additional reverse tandem duplications and dicentric and ring chromosomes. Four loci, on chromosome arms 2BS, 3DS, 4AL, and most likely on 7DL, were particularly susceptible to breakage. The BFB cycles produced high frequency of variegation for pigmentation of the aleurone layer of kernels and somatic chimeras for a morphological marker. With the exception of low mutation rate, the observed phenomena are consistent with the activity of a Ds-like element. However, it is not clear whether such an element, if indeed present, was of wheat or rye origin.

scholarly journals Rhythmic Serotonin N-Acetyltransferase mRNA Degradation Is Essential for the Maintenance of Its Circadian Oscillation

2005 ◽  
Vol 25 (8) ◽  
pp. 3232-3246 ◽  
Author(s):  
Tae-Don Kim ◽  
Jong-So Kim ◽  
Jong Heon Kim ◽  
Jihwan Myung ◽  
Hee-Don Chae ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Expression Patterns ◽  
Mrna Level ◽  
Mrna Degradation ◽  
Circadian Oscillation ◽  
Oscillatory Mechanism ◽  
Key Enzyme ◽  
Mrna Profile ◽  
Species Specific ◽  
Nuclear Ribonucleoprotein

ABSTRACT Serotonin N-acetyltransferase (arylalkylamine N-acetyltransferase [AANAT]) is the key enzyme in melatonin synthesis regulated by circadian rhythm. To date, our understanding of the oscillatory mechanism of melatonin has been limited to autoregulatory transcriptional and posttranslational regulations of AANAT mRNA. In this study, we identify three proteins from pineal glands that associate with cis-acting elements within species-specific AANAT 3′ untranslated regions to mediate mRNA degradation. These proteins include heterogeneous nuclear ribonucleoprotein R (hnRNP R), hnRNP Q, and hnRNP L. Their RNA-destabilizing function was determined by RNA interference and overexpression approaches. Expression patterns of these factors in pineal glands display robust circadian rhythm. The enhanced levels detected after midnight correlate with an abrupt decline in AANAT mRNA level. A mathematical model for the AANAT mRNA profile and its experimental evidence with rat pinealocytes indicates that rhythmic AANAT mRNA degradation mediated by hnRNP R, hnRNP Q, and hnRNP L is a key process in the regulation of its circadian oscillation.

Control of nitrogen assimilation in Stichococcus bacillaris by growth conditions

1987 ◽  
Vol 65 (3) ◽  
pp. 432-437 ◽  
Author(s):  
Iftikhar Ahmad ◽  
Johan A. Hellebust
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Assimilation ◽  
Continuous Light ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Dark Cycle ◽  
Continuous Darkness ◽  
Cell Carbon ◽  
Stichococcus Bacillaris ◽  
Mixotrophic Conditions

Stichococcus bacillaris Naeg. (Chlorophyceae) grown on a 12 h light: 12 h dark cycle divides synchronously under photoautotrophic conditions and essentially nonsynchronously under mixotrophic conditions. Photoassimilation of carbon under photoautotrophic conditions was followed by a decline in cell carbon content during the dark period, whereas under mixotrophic conditions cell carbon increased throughout the light–dark cycle. The rates of nitrogen assimilation by cultures grown on either nitrate or ammonium declined sharply during the dark, and these declines were most pronounced under photoautotrophic conditions. Photoautotrophic cells synthesized glutamine synthetase and NADPH – glutamate dehydrogenase (GDH) exclusively in the light, whereas in mixotrophic cells about 20% of the total synthesis of these enzymes during one light–dark cycle occurred in the dark. NADH–GDH was synthesized almost continuously over the entire light–dark cycle. In the dark, both under photoautotrophic and mixotrophic conditions, the alga contained more than 50% of glutamine synthetase in an inactive form, which was reactivated in vitro in the presence of mercaptoethanol and in vivo after returning the cultures to the light. The thermal stability of glutamine synthetase activity was less in light-harvested cells than in dark-harvested cells. The inactivation of glutamine synthetase did not occur in cultures growing either heterotrophically in continuous darkness or photoautotrophically in continuous light. This enzyme appears to be under thiol control only in cells grown under alternating light–dark conditions, irrespective of whether this light regime results in synchronous cell division or not.

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