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Kaur A, Goyal M. Metabolic adjustments in forage oat ( Avena sativa L.) genotypes under different sowing windows. PHYSIOLOGY AND MOLECULAR BIOLOGY OF PLANTS : AN INTERNATIONAL JOURNAL OF FUNCTIONAL PLANT BIOLOGY 2021; 27:2709-2725. [PMID: 35035131 PMCID: PMC8720123 DOI: 10.1007/s12298-021-01118-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 09/07/2021] [Accepted: 12/07/2021] [Indexed: 06/14/2023]
Abstract
The current investigation was aimed to study the influence of planting dates (9 Oct, 24 Oct, 13 Nov, 26 Nov, 11 Dec, and 26 Dec) and maturity stages (40, 50, and 60 DAS) on nitrogen metabolic enzymes and biochemical constituents. The experiment was laid out in randomized block design during the winter season of 2019 by using two oat genotypes (OL-10 and OL-11) with variable growing ability. The activity pattern of studied enzymes revealed upregulated nitrate assimilation during optimum (Oct 24) and sub-optimum (Oct 9 and Nov 13) planting dates but a reverse trend was observed during late planting dates; LPD (Nov 26, Dec 11, and Dec 26). The environmental constraints during LPD resulted in the accrual of nitrate above toxic levels (> 2000 ppm). The regression analysis depicted a significant relationship of nitrate assimilating enzymes and nitrate-N with temperature and sunshine hour. Examination of ammonia assimilation and transaminases suggested that the enzyme activities got uplifted during late planting dates but were stable or slightly low at optimum and sub-optimum ones. Additionally, OL-10 proved to be an N-efficient genotype in comparison with the OL-11 genotype because of its high N assimilation potential. Therefore, gaining a better understanding of planting time is crucial for sustainable livestock production.
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Affiliation(s)
- Aanchaldeep Kaur
- Department of Biochemistry, Punjab Agricultural University, Ludhiana, Punjab India
| | - Meenakshi Goyal
- Department of Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana, Punjab India
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Identification of a Novel Gene Encoding the Specialized Alanine Decarboxylase in Tea ( Camellia sinensis) Plants. Molecules 2019; 24:molecules24030540. [PMID: 30717241 PMCID: PMC6384637 DOI: 10.3390/molecules24030540] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 01/18/2019] [Accepted: 01/27/2019] [Indexed: 11/17/2022] Open
Abstract
Theanine, a unique amino acid in Camellia sinensis, accounts for more than 50% of total free amino acids in tea and has a significant contribution to the quality of green tea. Previous research indicated that theanine is synthesized from glutamic acid (Glu) and ethylamine mainly in roots, and that theanine accumulation depends on the availability of ethylamine which is derived from alanine (Ala) decarboxylation catalyzed by alanine decarboxylase (AlaDC). However, the specific gene encoding AlaDC protein remains to be discovered in tea plants or in other species. To explore the gene of AlaDC in tea plants, the differences in theanine contents and gene expressions between pretreatment and posttreatment of long-time nitrogen starvation were analyzed in young roots of two tea cultivars. A novel gene annotated as serine decarboxylase (SDC) was noted for its expression levels, which showed high consistency with theanine content, and the expression was remarkably high in young roots under sufficient nitrogen condition. To verify its function, full-length complementary DNA (cDNA) of this candidate gene was cloned from young roots of tea seedlings, and the target protein was expressed and purified from Escherichia coli (E. coli). The enzymatic activity of the protein for Ala and Ser was measured in vitro using ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS). The results illustrated that the target protein could catalyze the decarboxylation of Ala despite of its high similarity with SDC from other species. Therefore, this novel gene was identified as AlaDC and named CsAlaDC. Furthermore, the gene expression levels of CsAlaDC in different tissues of tea plants were also quantified with quantitative real-time PCR (qRT-PCR). The results suggest that transcription levels of CsAlaDC in root tissues are significantly higher than those in leaf tissues. That may explain why theanine biosynthesis preferentially occurs in the roots of tea plants. The expression of the gene was upregulated when nitrogen was present, suggesting that theanine biosynthesis is regulated by nitrogen supply and closely related to nitrogen metabolism for C. sinensis. The results of this study are significant supplements to the theanine biosynthetic pathway and provide evidence for the differential accumulation of theanine between C. sinensis and other species.
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Ma G, Liu W, Li S, Zhang P, Wang C, Lu H, Wang L, Xie Y, Ma D, Kang G. Determining the Optimal N Input to Improve Grain Yield and Quality in Winter Wheat With Reduced Apparent N Loss in the North China Plain. FRONTIERS IN PLANT SCIENCE 2019; 10:181. [PMID: 30853966 PMCID: PMC6396033 DOI: 10.3389/fpls.2019.00181] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 02/05/2019] [Indexed: 05/06/2023]
Abstract
Excessive or improper nitrogen (N) application rates negatively affect crop production and thereby environmental quality, particularly for winter wheat production in the North China Plain. Therefore, it is very important to optimize N fertilizer input to balance grain yield, environmental risk, and benefits under irrigated conditions. Three long-term stationary field experiments including five N levels, from 0 to 300 kg ha-1 [0 (N0), 90 (N90), 180 (N180), 240 (N240), and 300 (N300) kg ha-1] were carried out to investigate the effects of N regime on wheat yield, photosynthesis, and N balance at different sites. The grain yield and protein content increased quadratically with N rate, and the maximum values were 8087 kg ha-1 and 13.9% at N application rates of 250 and 337 kg N ha-1, respectively. N application increased the photosynthetic fluorescence parameters (Pn, Gs, and Tr) and N metabolism enzyme activities (NR and GS) which then increased grain yield. The leaching of soil nitrate into the deeper soil layers ( > 100 cm) increased with higher N fertilization and experimental years. The partial factor productivity (PFPN) was decreased by N because the apparent N loss increased with N application rate. In order to balance grain yield, N use efficiency (NUE), and N loss, the recommended N rate should be 120-171 kg N ha-1, and the corresponding yields and apparent N loss were 7278-7787 ka ha-1 and 22-37 kg ha-1, respectively.
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Affiliation(s)
- Geng Ma
- College of Agronomy, Henan Agricultural University, Zhengzhou, China
| | - Weixing Liu
- College of Agronomy, Henan Agricultural University, Zhengzhou, China
| | - Shasha Li
- College of Agronomy, Henan Agricultural University, Zhengzhou, China
| | - Panpan Zhang
- College of Agronomy, Henan Agricultural University, Zhengzhou, China
| | - Chenyang Wang
- College of Agronomy, Henan Agricultural University, Zhengzhou, China
- State Key Laboratory of Wheat and Maize Crop Science, Henan Agricultural University, Zhengzhou, China
- National Engineering Research Centre for Wheat, Henan Agricultural University, Zhengzhou, China
- *Correspondence: Chenyang Wang,
| | - Hongfang Lu
- College of Agronomy, Henan Agricultural University, Zhengzhou, China
- State Key Laboratory of Wheat and Maize Crop Science, Henan Agricultural University, Zhengzhou, China
- National Engineering Research Centre for Wheat, Henan Agricultural University, Zhengzhou, China
| | - Lifang Wang
- College of Agronomy, Henan Agricultural University, Zhengzhou, China
- State Key Laboratory of Wheat and Maize Crop Science, Henan Agricultural University, Zhengzhou, China
- National Engineering Research Centre for Wheat, Henan Agricultural University, Zhengzhou, China
| | - Yingxin Xie
- College of Agronomy, Henan Agricultural University, Zhengzhou, China
- State Key Laboratory of Wheat and Maize Crop Science, Henan Agricultural University, Zhengzhou, China
- National Engineering Research Centre for Wheat, Henan Agricultural University, Zhengzhou, China
| | - Dongyun Ma
- College of Agronomy, Henan Agricultural University, Zhengzhou, China
- State Key Laboratory of Wheat and Maize Crop Science, Henan Agricultural University, Zhengzhou, China
- National Engineering Research Centre for Wheat, Henan Agricultural University, Zhengzhou, China
| | - Guozhang Kang
- College of Agronomy, Henan Agricultural University, Zhengzhou, China
- State Key Laboratory of Wheat and Maize Crop Science, Henan Agricultural University, Zhengzhou, China
- National Engineering Research Centre for Wheat, Henan Agricultural University, Zhengzhou, China
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Trucillo Silva I, Abbaraju HKR, Fallis LP, Liu H, Lee M, Dhugga KS. Biochemical and genetic analyses of N metabolism in maize testcross seedlings: 1. Leaves. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2017; 130:1453-1466. [PMID: 28444412 DOI: 10.1007/s00122-017-2900-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 03/27/2017] [Indexed: 05/18/2023]
Abstract
Aside from the identification of 32 QTL for N metabolism in the seedling leaves of a maize testcross population, alanine aminotransferase was found to be a central enzyme in N assimilation. Excessive application of nitrogen (N) fertilizer to grow commercial crops like maize is a cause of concern because of the runoff of excess N into streams and rivers. Breeding maize with improved N use efficiency (NUE) would reduce environmental pollution as well as input costs for the farmers. An understanding of the genetics underlying N metabolism is key to breeding for NUE. From a set of 176 testcrosses derived from the maize IBMsyn10 population grown in hydroponics, we analyzed the youngest fully expanded leaf at four-leaf stage for enzymes and metabolites related to N metabolism. Three enzymes, along with one metabolite explained 24% of the variation in shoot dry mass. Alanine aminotransferase (AlaAT) stood out as the key enzyme in maintaining the cellular level of glutamate as it alone explained 58% of the variation in this amino acid. Linkage mapping revealed 32 quantitative trait loci (QTL), all trans to the genomic positions of the structural genes for various enzymes of N assimilation. The QTL models for different traits accounted for 7-31% of the genetic variance, whereas epistasis was generally not significant. Five coding regions underlying 1-LOD QTL confidence intervals were identified for further validation studies. Our results provide evidence for the key role of AlaAT in N assimilation likely through homeostatic control of glutamate levels in the leaf cells. The two QTL identified for this enzyme would help to select desirable recombinants for improved N assimilation.
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Affiliation(s)
| | - Hari Kishan R Abbaraju
- Trait Discovery and Technology, DuPont Pioneer, Johnston, IA, 50131, USA
- AVX Corporation, One AVX Blvd., Fountain Inn, SC, 29644, USA
| | - Lynne P Fallis
- Trait Discovery and Technology, DuPont Pioneer, Johnston, IA, 50131, USA
- Department of Genetics, Developmental and Cell Biology, Iowa State University, Ames, IA, 50011, USA
| | - Hongjun Liu
- State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai'an, 271018, China
| | - Michael Lee
- Department of Agronomy, Iowa State University, Ames, IA, 50011, USA.
| | - Kanwarpal S Dhugga
- Trait Discovery and Technology, DuPont Pioneer, Johnston, IA, 50131, USA.
- International Center for Maize and Wheat Improvement (CIMMYT), El Batan, 56237, E.d. Mexico, Mexico.
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Zhang M, Ma D, Ma G, Wang C, Xie X, Kang G. Responses of glutamine synthetase activity and gene expression to nitrogen levels in winter wheat cultivars with different grain protein content. J Cereal Sci 2017. [DOI: 10.1016/j.jcs.2017.01.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Yang H, Meng Y, Chen B, Zhang X, Wang Y, Zhao W, Zhou Z. How Integrated Management Strategies Promote Protein Quality of Cotton Embryos: High Levels of Soil Available N, N Assimilation and Protein Accumulation Rate. FRONTIERS IN PLANT SCIENCE 2016; 7:1118. [PMID: 27532007 PMCID: PMC4969568 DOI: 10.3389/fpls.2016.01118] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 07/13/2016] [Indexed: 05/24/2023]
Abstract
Cottonseed is widely used as a source of ruminant feed and for industrial purposes. Therefore, there is a tremendous need to improve the nutritional value of cotton embryos. In this study, a conventional management (CM) and two integrated cotton management strategies (IMS1, IMS2) were performed at two soil fertility levels to study the relationships among soil N, N assimilation, embryonic protein accumulation and protein quality. The levels of proteins, essential amino acids, and semi-essential amino acids, especially those of glutamate, lysine, and methionine, were higher in IMS1 and IMS2 embryos than in CM embryos. These changes were significantly positively correlated with the soil-available N content, glutamine synthetase activity and peak value of protein accumulation rate and were negatively correlated with the free amino acid level. These results illustrated that integrated management strategies, especially the rates and timing of N application, raise the level of soil available N, which is beneficial for N assimilation in developing cotton embryos. The protein content was limited by the rate of protein accumulation rather than by the free amino acid content. The combination of target yield fertilization, a growth-driven N application schedule, a high plant density and the seedling raising with bio-organic fertilizer can substantially improve protein quality in cotton embryos, especially at a soil with low soil organic matter and total nitrogen.
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Affiliation(s)
| | | | - BingLin Chen
- Key Laboratory of Crop Physiology and Ecology, Ministry of Agriculture, Nanjing Agricultural University and Jiangsu Collaborative Innovation Center for Modern Crop ProductionNanjing, China
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Seth CS, Misra V. Changes in C-N metabolism under elevated CO2 and temperature in Indian mustard (Brassica juncea L.): an adaptation strategy under climate change scenario. JOURNAL OF PLANT RESEARCH 2014; 127:793-802. [PMID: 25246072 DOI: 10.1007/s10265-014-0664-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 07/26/2014] [Indexed: 06/03/2023]
Abstract
The present study was performed to investigate the possible role of carbon (C) and nitrogen (N) metabolism in adaptation of Indian mustard (Brassica juncea L.) growing under ambient (370 ± 15 ppm) and elevated CO2 (700 ± 15 ppm), and jointly in elevated CO2 and temperature (30/22 °C for day/night). The key enzymes responsible for C-N metabolism were studied in different samples of Brassica juncea L. collected from ambient (AMB), elevated (ELE) and ELExT growth conditions. Total percent amount of C and N in leaves were particularly estimated to establish a clear understanding of aforesaid metabolism in plant adaptation. Furthermore, key morphological and physiological parameters such as plant height, leaf area index, dry biomass, net photosynthetic rate, stomatal conductance, transpiration, total protein and chlorophyll contents were also studied in relation to C/N metabolism. The results indicated that the C-metabolizing enzymes, such as (ribulose-1,5-bisphosphate carboxylase/oxygenase, phosphoenolpyruvate carboxylase, malate dehydrogenase, NAD-malic enzyme, NADP-malic enzyme and citrate synthase) and the N-metabolizing enzymes, such as (aspartate amino transferase, glutamine synthetase, nitrate reductase and nitrite reductase) showed significantly (P < 0.05) higher activities along with the aforesaid physiological and biochemical parameters in order of ELE > ELExT > AMB growth conditions. This is also evident by significant (P < 0.05) increase in percent contents of C and N in leaves as per said order. These findings suggested that improved performance of C-N metabolism could be a possible approach for CO2 assimilation and adaptation in Brassica juncea L. against elevated CO2 and temperature prevailing in climate change scenarios.
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Barbosa JM, Singh NK, Cherry JH, Locy RD. Nitrate uptake and utilization is modulated by exogenous gamma-aminobutyric acid in Arabidopsis thaliana seedlings. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2010; 48:443-50. [PMID: 20303774 DOI: 10.1016/j.plaphy.2010.01.020] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Revised: 01/20/2010] [Accepted: 01/27/2010] [Indexed: 05/19/2023]
Abstract
Exogenously applied GABA modulates root growth by inhibition of root elongation when seedlings were grown in vitro on full-strength Murashige and Skoog (MS) salts, but root elongation was stimulated when seedlings were grown on 1/8 strength MS salts. When the concentration of single ions in MS salts was individually varied, the control of growth between inhibition and stimulation was found to be related to the level of nitrate (NO(3)(-)) in the growth medium. At NO(3)(-) concentrations below 40 mM (full-strength MS salts level), root growth was stimulated by the addition of GABA to the growth medium; whereas at concentrations above 40 mM NO(3)(-), the addition of GABA to the growth medium inhibited root elongation. GABA promoted NO(3)(-) uptake at low NO(3)(-), while GABA inhibited NO(3)(-) uptake at high NO(3)(-). Activities of several enzymes involved in nitrogen and carbon metabolism including nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (NADH-GOGAT), NADP-dependent isocitrate dehydrogenase (NADP-ICDH), and phosphoenol pyruvate carboxylase (PEPCase) were regulated by GABA in the growth medium. Supplementing 1/8 strength MS medium with 50 mM GABA enhanced the activities of all of the above enzymes except ICDH activities in root tissues. However, at full-strength MS, GABA showed no inhibitory effect on the activities of these enzymes, except on GS in both root and shoot tissues, and PEPCase activity in shoot tissues. Exogenous GABA increased the amount of NR protein rather than its activation status in the tissues. This study shows that GABA affects the growth of Arabidopsis, possibly by acting as a signaling molecule, modulating the activity of enzymes involved in primary nitrogen metabolism and nitrate uptake.
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Affiliation(s)
- Jose M Barbosa
- Department of Biology & Environmental Sciences, 615 McCallie Ave, University of Tennessee at Chattanooga, Chattanooga, TN 37403, USA
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Bernard SM, Møller ALB, Dionisio G, Kichey T, Jahn TP, Dubois F, Baudo M, Lopes MS, Tercé-Laforgue T, Foyer CH, Parry MAJ, Forde BG, Araus JL, Hirel B, Schjoerring JK, Habash DZ. Gene expression, cellular localisation and function of glutamine synthetase isozymes in wheat (Triticum aestivum L.). PLANT MOLECULAR BIOLOGY 2008; 67:89-105. [PMID: 18288574 DOI: 10.1007/s11103-008-9303-y] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Accepted: 01/28/2008] [Indexed: 05/25/2023]
Abstract
We present the first cloning and study of glutamine synthetase (GS) genes in wheat (Triticum aestivum L.). Based on sequence analysis, phylogenetic studies and mapping data, ten GS sequences were classified into four sub-families: GS2 (a, b and c), GS1 (a, b and c), GSr (1 and 2) and GSe (1 and 2). Phylogenetic analysis showed that the wheat GS sub-families together with the GS genes from other monocotyledonous species form four distinct clades. Immunolocalisation studies in leaves, stems and rachis in plants at flowering showed GS protein to be present in parenchyma, phloem companion and perifascicular sheath cells. In situ localisation confirmed that GS1 transcripts were present in the perifascicular sheath cells whilst those for GSr were confined to the vascular cells. Studies of the expression and protein profiles showed that all GS sub-families were differentially expressed in the leaves, peduncle, glumes and roots. Expression of GS genes in leaves was developmentally regulated, with both GS2 and GS1 assimilating or recycling ammonia in leaves during the period of grain development and filling. During leaf senescence the cytosolic isozymes, GS1 and GSr, were the predominant forms, suggesting major roles in assimilating ammonia during the critical phases of remobilisation of nitrogen to the grain. A preliminary analysis of three different wheat genotypes showed that the ratio of leaf GS2 protein to GS1 protein was variable. Use of this genetic variation should inform future efforts to modulate this enzyme for pre-breeding efforts to improve nitrogen use in wheat.
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Affiliation(s)
- Stéphanie M Bernard
- Plant Science Department, Centre for Crop Genetic Improvement, Rothamsted Research, Harpenden, Hertfordshire, UK
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Habash DZ, Bernard S, Schondelmaier J, Weyen J, Quarrie SA. The genetics of nitrogen use in hexaploid wheat: N utilisation, development and yield. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2007; 114:403-19. [PMID: 17180378 DOI: 10.1007/s00122-006-0429-5] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Accepted: 10/06/2006] [Indexed: 05/13/2023]
Abstract
A genetic study is presented for traits relating to nitrogen use in wheat. Quantitative trait loci (QTLs) were established for 21 traits relating to growth, yield and leaf nitrogen (N) assimilation during grain fill in hexaploid wheat (Triticum aestivum L.) using a mapping population from the cross Chinese Spring x SQ1. Glutamine synthetase (GS) isozymes and estimated locations of 126 genes were placed on the genetic map. QTLs for flag leaf GS activity, soluble protein, extract colour and fresh weight were found in similar regions implying shared control of leaf metabolism and leaf size. Flag leaf traits were negatively associated with days to anthesis both phenotypically and genetically, demonstrating the complex interactions of metabolism with development. One QTL cluster for GS activity co-localised with a GS2 gene mapped on chromosome 2A, and another with the mapped GSr gene on 4A. QTLs for GS activity were invariably co-localised with those for grain N, with increased activity associated with higher grain N, but with no or negative correlations with grain yield components. Peduncle N was positively correlated, and QTLs co-localised, with grain N and flag leaf N assimilatory traits, suggesting that stem N can be indicative of grain N status in wheat. A major QTL for ear number per plant was identified on chromosome 6B which was negatively co-localised with leaf fresh weight, peduncle N, grain N and grain yield. This locus is involved in processes defining the control of tiller number and consequently assimilate partitioning and deserves further examination.
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Affiliation(s)
- Dimah Z Habash
- Crop Performance and Improvement Division, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.
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Kumar N, Kumar S, Vats SK, Ahuja PS. Effect of altitude on the primary products of photosynthesis and the associated enzymes in barley and wheat. PHOTOSYNTHESIS RESEARCH 2006; 88:63-71. [PMID: 16450048 DOI: 10.1007/s11120-005-9028-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2005] [Accepted: 10/19/2005] [Indexed: 05/06/2023]
Abstract
There is little information available on the primary products of photosynthesis and the change in the activity of the associated enzymes with altitude. We studied the same in varieties of barley and wheat grown at 1300 (low altitude, LA) and 4200 m (high altitude, HA) elevations above mean sea level in the western Himalayas. Plants at both the locations had similar photosynthetic rates, leaf water potential and the chlorophyll fluorescence kinetics. The short-term radio-labelling experiments in leaves showed appearance of (14)CO(2) in phosphoglyceric acid and sugar phosphates in plants at both the LA and HA, suggesting a major role of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in CO(2) fixation in the plants at two altitudes, whereas the appearance of labelled carbon in aspartate (Asp) and glutamate (Glu) at HA suggested a role of phosphoenolpyruvate carboxylase (PEPCase) in photosynthesis metabolism. Plants at HA had significantly higher activities of PEPCase, carboxylase and oxygenase activity of Rubisco, aspartate aminotransferase (AspAT), and glutamine synthetase (GS). However, the activities of malate dehydrogenase, NAD-malic enzyme and citrate synthase were similar at the two locations. Such an altered metabolism at HA suggested that PEPCase probably captured CO(2) directly from the atmosphere and/or that generated metabolically e.g. from photorespiration at HA. Higher oxygenase activity at HA suggests high photorespiratory activity. OAA thus produced could be additionally channelised for Asp synthesis using Glu as a source of ammonia. Higher GS activity ensures higher assimilation rate of NH(3) and the synthesis of Glu through GS-GOGAT (glutamine:2-oxoglutarate aminotransferase) pathway, also as supported by the appearance of radiolabel in Glu at HA. Enhanced PEPCase activity coupled with higher activities of AspAT and GS suggests a role in conserving C and N in the HA environment.
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Affiliation(s)
- Narinder Kumar
- Biotechnology Division, Institute of Himalayan Bioresource Technology, 176 061, Palampur, HP, India
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Chaffei C, Gouia H, Masclaux C, Ghorbel MH. [Reversibility of the effects of cadmium on the growth and nitrogen metabolism in the tomato(Lycopersicon esculentum)]. C R Biol 2003; 326:401-12. [PMID: 12892045 DOI: 10.1016/s1631-0691(03)00119-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In order to better understand the effects of heavy metals on the growth of plants, we decided to perform recovering experiments by following both chemical and physiological parameters in cadmium pre-stressed tomato seedlings after cadmium had been removed from the nutrient solution. The work shows that cadmium suppression results in resumption of growth activity. The biomass of leaves and stems rose steadily. The increase in root biomass exceeded those of leaves and stems. At the same time, nitrate content was increased to reach the level obtained with unstressed controls. In all the organs studied, the activities of the enzymes involved in the anabolic nitrogen primary assimilation pathways (nitrate reductase (NR), nitrite reductase (NiR) and glutamine synthetase (GS) soared after that cadmium had been removed. While NAD(+)-dependent glutamate dehydrogenase (GDH-NAD+) activity also rose progressively during the recovering time, the cognate NADH-dependent glutamate dehydrogenase (GDH-NADH) activity decreased. This result allows us to propose that the ammonia produced by the stress-induced protein catabolism is detoxified and re-assimilated by the GDH-NADH isoenzyme. On the basis of these results, we will discuss the ability of the plant to dilute the effects of pollutants during the recovering period. An important outcome of this work is that a transient contamination of the culture medium by pollutants is not necessarily followed by a significant depreciation in product yield or quality.
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Affiliation(s)
- Chiraz Chaffei
- Laboratoire de physiologie végétale, Unité de recherche Nutrition et métabolisme azotés et protéines de stress, Département des sciences biologiques, Université de Tunis El Manar, 1060 Tunis, Tunisie.
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Fuentes SI, Allen DJ, Ortiz-Lopez A, Hernández G. Over-expression of cytosolic glutamine synthetase increases photosynthesis and growth at low nitrogen concentrations. JOURNAL OF EXPERIMENTAL BOTANY 2001; 52:1071-81. [PMID: 11432923 DOI: 10.1093/jexbot/52.358.1071] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Nitrogen, which is a major limiting nutrient for plant growth, is assimilated as ammonium by the concerted action of glutamine synthetase (GS) and glutamate synthase (GOGAT). GS catalyses the critical incorporation of inorganic ammonium into the amino acid glutamine. Two types of GS isozymes, located in the cytosol (GS1) and in the chloroplast (GS2) have been identified in plants. Tobacco (Nicotiana tabacum) transformants, over-expressing GS1 driven by the constitutive CaMV 35S promoter were analysed. GS in leaves of GS-5 and GS-8 plants was up-regulated, at the level of RNA and proteins. These transgenic plants had six times higher leaf GS activity than controls. Under optimum nitrogen fertilization conditions there was no effect of GS over-expression on photosynthesis or growth. However, under nitrogen starvation the GS transgenics had c. 70% higher shoot and c. 100% greater root dry weight as well as 50% more leaf area than low nitrogen controls. This was achieved by the maintenance of photosynthesis at rates indistinguishable from plants under high nitrogen, while photosynthesis in control plants was inhibited by 40-50% by nitrogen deprivation. It was demonstrated that manipulation of GS activity has the potential to maintain crop photosynthetic productivity while reducing nitrogen fertilization and the concomitant pollution.
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Affiliation(s)
- S I Fuentes
- Centro de Investigación sobre Fijación de Nitrógeno, UNAM, Apartado Postal 565-A, Cuernavaca, Mor. México
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Mesnard F, Marty D, Gillet-Manceau F, Fliniaux MA, Monti JP. Glutamine synthetase activity in Solanaceous cell suspensions accumulating alkaloids or not. 13C NMR and enzymatic assay. COMPTES RENDUS DE L'ACADEMIE DES SCIENCES. SERIE III, SCIENCES DE LA VIE 1999; 322:743-8. [PMID: 10547716 DOI: 10.1016/s0764-4469(00)80032-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The metabolism of labelled pyruvate followed by 13C NMR and the measure of glutamine synthetase (GS) showed, according to previous results, a high activity of this enzyme in suspension cells of Nicotiana plumbaginifolia. This activity could derive glutamate from the alkaloid synthesizing pathways. However, a recent work showed that the rate of the GS gene transcription was inversely proportional to the Gln/Glu ratio. The measures of Gln and Glu concentrations in Nicotiana plumbaginifolia cells revealed that high GS activity correlates with the weak value of Gln/Glu ratio. Therefore, the hypothesis of GS dysfunctioning for the non-biosynthesis of alkaloids in N. plumbaginifolia suspension cells can be discarded. This conclusion is strengthened by the results obtained when using a GS inhibitor.
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Affiliation(s)
- F Mesnard
- Laboratoire de biophysique, faculté de pharmacie, Amiens, France
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Palomo J, Gallardo F, Suarez MF, Canovas FM. Purification and characterization of NADP+-linked isocitrate dehydrogenase from scots pine . Evidence for different physiological roles of the enzyme in primary development. PLANT PHYSIOLOGY 1998; 118:617-26. [PMID: 9765548 PMCID: PMC34838 DOI: 10.1104/pp.118.2.617] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/1998] [Accepted: 07/10/1998] [Indexed: 05/19/2023]
Abstract
NADP+-isocitrate dehydrogenase (NADP+-IDH; EC 1.1.1.42) is involved in the supply of 2-oxoglutarate for ammonia assimilation and glutamate synthesis in higher plants through the glutamine synthetase/glutamate synthase (GS/GOGAT) cycle. Only one NADP+-IDH form of cytosolic localization was detected in green cotyledons of pine (Pinus spp.) seedlings. The pine enzyme was purified and exhibited molecular and kinetic properties similar to those described for NADP+-IDH from angiosperm, with a higher catalytic efficiency (10(5) M-1 s-1) than the deduced efficiencies for GS and GOGAT in higher plants. A polyclonal antiserum was raised against pine NADP+-IDH and used to assess protein expression in the seedlings. Steady-state levels of NADP+-IDH were coordinated with GS during seed germination and were associated with GS/GOGAT enzymes during chloroplast biogenesis, suggesting that NADP+-IDH is involved in the provision of carbon skeletons for the synthesis of nitrogen-containing molecules. However, a noncoordinated pattern of NADP+-IDH and GS/GOGAT was observed in advanced stages of cotyledon development and in the hypocotyl. A detailed analysis in hypocotyl sections revealed that NADP+-IDH abundance was inversely correlated with the presence of GS, GOGAT, and ribulose-1,5-bisphosphate carboxylase/oxygenase but was associated with the differentiation of the organ. These results cannot be explained by the accepted role of the enzyme in nitrogen assimilation and strongly suggest that NADP+-IDH may have other, as-yet-unknown, biological functions.
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Affiliation(s)
- J Palomo
- Laboratorio de Bioquimica y Biologia Molecular, Facultad de Ciencias, Universidad de Malaga and Instituto Andaluz de Biotecnologia, Campus de Teatinos, E-29071 Malaga, Spain
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