Cd-Stress on Nitrogen Assimilation
Identifieur interne : 001887 ( Istex/Corpus ); précédent : 001886; suivant : 001888Cd-Stress on Nitrogen Assimilation
Auteurs : N. Boussama ; O. Ouariti ; A. Suzuki ; M. H. GhorbalSource :
- Journal of Plant Physiology [ 0176-1617 ] ; 1999.
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Abstract
Summary: Nitrate assimilation in higher plants is the principal biosynthetic pathway leading to glutamate, required for synthesis of particular metabolites that participate in mechanisms of biochemical adaptation to heavy metal stress such as cadmium. Exposure of maize (Zea mays L.) seedlings to increasing cadmium concentrations for 12 days resulted in a significant decrease in nitrate content coupled to inhibition in activities of the enzymes nitrate reductase (EC 1.6.6.1), nitrite reductase (EC 1.6.6.4), glutamine synthetase (EC 6.3.1.2), ferredoxin-glutamate synthase (EC 1.4.7.1), and NADH-glutamate synthase (EC 1.4.1.14). Patterns of NADH- (aminating) and NAD+- (deaminating) glutamate dehydrogenase (EC 1.4.1.2) activities were opposed, with a great increase in the aminating direction. Concurrently, cadmium treatments promoted an increase in protease activity as well as accumulation of ammonia in tissues. These changes in enzyme activities were accompanied by a loss in total amino acids and proteins in both shoots and roots. However, of all amino acids quantified, glutamate, proline, lysine, methionine, and glycine showed a remarkable accumulation in cadmium treated plants, in comparison to control ones. The increased level of glutamate paralleled the elevated contents of γ-glutamylcysteine and glutathione in response to cadmium treatments. The magnitude of changes in all parameters investigated was concentration-dependent. Considered together, metabolite analysis and enzymatic measurements showed that cadmium induces a substantial shift in the operative pathways of ammonia assimilation, and suggested that the induction of NADH-glutamate dehydrogenase activity under cadmium stress may provide glutamate required for enhancing the synthesis of proline, γ-glutamylcysteine and glutathione, which is a common response to cadmium stress conditions. The possible association of these findings with cadmium-binding peptides is discussed.
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DOI: 10.1016/S0176-1617(99)80110-2
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<record><TEI wicri:istexFullTextTei="biblStruct"><teiHeader><fileDesc><titleStmt><title xml:lang="en">Cd-Stress on Nitrogen Assimilation</title><author><name sortKey="Boussama, N" sort="Boussama, N" uniqKey="Boussama N" first="N." last="Boussama">N. Boussama</name><affiliation><mods:affiliation>Laboratoire de Physiologie Végétale «Nutrition et Métabolisme Azotés» (E 20/C 09), Département des Sciences Biologiques, Faculté des Sciences de Tunis, Campus Universitaire-1060 Tunis, Tunisia</mods:affiliation></affiliation></author><author><name sortKey="Ouariti, O" sort="Ouariti, O" uniqKey="Ouariti O" first="O." last="Ouariti">O. Ouariti</name><affiliation><mods:affiliation>Laboratoire de Physiologie Végétale «Nutrition et Métabolisme Azotés» (E 20/C 09), Département des Sciences Biologiques, Faculté des Sciences de Tunis, Campus Universitaire-1060 Tunis, Tunisia</mods:affiliation></affiliation></author><author><name sortKey="Suzuki, A" sort="Suzuki, A" uniqKey="Suzuki A" first="A." last="Suzuki">A. Suzuki</name><affiliation><mods:affiliation>Laboratoire du Métabolisme et de la Nutrition des Plantes, INRA, Route de Saint-Cyr, Versailles F-78026 Cedex, France</mods:affiliation></affiliation></author><author><name sortKey="Ghorbal, M H" sort="Ghorbal, M H" uniqKey="Ghorbal M" first="M. H." last="Ghorbal">M. H. Ghorbal</name><affiliation><mods:affiliation>Laboratoire de Physiologie Végétale «Nutrition et Métabolisme Azotés» (E 20/C 09), Département des Sciences Biologiques, Faculté des Sciences de Tunis, Campus Universitaire-1060 Tunis, Tunisia</mods:affiliation></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">ISTEX</idno><idno type="RBID">ISTEX:F3C0073941998680620E4A242C734587C4DCBC27</idno><date when="1999" year="1999">1999</date><idno type="doi">10.1016/S0176-1617(99)80110-2</idno><idno type="url">https://api.istex.fr/document/F3C0073941998680620E4A242C734587C4DCBC27/fulltext/pdf</idno><idno type="wicri:Area/Istex/Corpus">001887</idno><idno type="wicri:explorRef" wicri:stream="Istex" wicri:step="Corpus" wicri:corpus="ISTEX">001887</idno></publicationStmt><sourceDesc><biblStruct><analytic><title level="a" type="main" xml:lang="en">Cd-Stress on Nitrogen Assimilation</title><author><name sortKey="Boussama, N" sort="Boussama, N" uniqKey="Boussama N" first="N." last="Boussama">N. Boussama</name><affiliation><mods:affiliation>Laboratoire de Physiologie Végétale «Nutrition et Métabolisme Azotés» (E 20/C 09), Département des Sciences Biologiques, Faculté des Sciences de Tunis, Campus Universitaire-1060 Tunis, Tunisia</mods:affiliation></affiliation></author><author><name sortKey="Ouariti, O" sort="Ouariti, O" uniqKey="Ouariti O" first="O." last="Ouariti">O. Ouariti</name><affiliation><mods:affiliation>Laboratoire de Physiologie Végétale «Nutrition et Métabolisme Azotés» (E 20/C 09), Département des Sciences Biologiques, Faculté des Sciences de Tunis, Campus Universitaire-1060 Tunis, Tunisia</mods:affiliation></affiliation></author><author><name sortKey="Suzuki, A" sort="Suzuki, A" uniqKey="Suzuki A" first="A." last="Suzuki">A. Suzuki</name><affiliation><mods:affiliation>Laboratoire du Métabolisme et de la Nutrition des Plantes, INRA, Route de Saint-Cyr, Versailles F-78026 Cedex, France</mods:affiliation></affiliation></author><author><name sortKey="Ghorbal, M H" sort="Ghorbal, M H" uniqKey="Ghorbal M" first="M. H." last="Ghorbal">M. H. Ghorbal</name><affiliation><mods:affiliation>Laboratoire de Physiologie Végétale «Nutrition et Métabolisme Azotés» (E 20/C 09), Département des Sciences Biologiques, Faculté des Sciences de Tunis, Campus Universitaire-1060 Tunis, Tunisia</mods:affiliation></affiliation></author></analytic><monogr></monogr><series><title level="j">Journal of Plant Physiology</title><title level="j" type="abbrev">JPLPH</title><idno type="ISSN">0176-1617</idno><imprint><publisher>ELSEVIER</publisher><date type="published" when="1999">1999</date><biblScope unit="volume">155</biblScope><biblScope unit="issue">3</biblScope><biblScope unit="page" from="310">310</biblScope><biblScope unit="page" to="317">317</biblScope></imprint><idno type="ISSN">0176-1617</idno></series></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0176-1617</idno></seriesStmt></fileDesc><profileDesc><textClass><keywords scheme="KwdEn" xml:lang="en"><term>GDH</term><term>GOGAT</term><term>GS</term><term>GSH</term><term>NR</term><term>NiR</term><term>Zea mays</term><term>amino acids</term><term>cadmium stress</term><term>glutamate</term><term>glutathione</term><term>nitrate</term><term>nitrogen assimilating enzymes</term><term>proline</term><term>γ-EC</term><term>γ-glutamylcysteine</term></keywords></textClass><langUsage><language ident="en">en</language></langUsage></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">Summary: Nitrate assimilation in higher plants is the principal biosynthetic pathway leading to glutamate, required for synthesis of particular metabolites that participate in mechanisms of biochemical adaptation to heavy metal stress such as cadmium. Exposure of maize (Zea mays L.) seedlings to increasing cadmium concentrations for 12 days resulted in a significant decrease in nitrate content coupled to inhibition in activities of the enzymes nitrate reductase (EC 1.6.6.1), nitrite reductase (EC 1.6.6.4), glutamine synthetase (EC 6.3.1.2), ferredoxin-glutamate synthase (EC 1.4.7.1), and NADH-glutamate synthase (EC 1.4.1.14). Patterns of NADH- (aminating) and NAD+- (deaminating) glutamate dehydrogenase (EC 1.4.1.2) activities were opposed, with a great increase in the aminating direction. Concurrently, cadmium treatments promoted an increase in protease activity as well as accumulation of ammonia in tissues. These changes in enzyme activities were accompanied by a loss in total amino acids and proteins in both shoots and roots. However, of all amino acids quantified, glutamate, proline, lysine, methionine, and glycine showed a remarkable accumulation in cadmium treated plants, in comparison to control ones. The increased level of glutamate paralleled the elevated contents of γ-glutamylcysteine and glutathione in response to cadmium treatments. The magnitude of changes in all parameters investigated was concentration-dependent. Considered together, metabolite analysis and enzymatic measurements showed that cadmium induces a substantial shift in the operative pathways of ammonia assimilation, and suggested that the induction of NADH-glutamate dehydrogenase activity under cadmium stress may provide glutamate required for enhancing the synthesis of proline, γ-glutamylcysteine and glutathione, which is a common response to cadmium stress conditions. The possible association of these findings with cadmium-binding peptides is discussed.</div></front></TEI><istex><corpusName>elsevier</corpusName><author><json:item><name>N. Boussama</name><affiliations><json:string>Laboratoire de Physiologie Végétale «Nutrition et Métabolisme Azotés» (E 20/C 09), Département des Sciences Biologiques, Faculté des Sciences de Tunis, Campus Universitaire-1060 Tunis, Tunisia</json:string></affiliations></json:item><json:item><name>O. Ouariti</name><affiliations><json:string>Laboratoire de Physiologie Végétale «Nutrition et Métabolisme Azotés» (E 20/C 09), Département des Sciences Biologiques, Faculté des Sciences de Tunis, Campus Universitaire-1060 Tunis, Tunisia</json:string></affiliations></json:item><json:item><name>A. Suzuki</name><affiliations><json:string>Laboratoire du Métabolisme et de la Nutrition des Plantes, INRA, Route de Saint-Cyr, Versailles F-78026 Cedex, France</json:string></affiliations></json:item><json:item><name>M.H. Ghorbal</name><affiliations><json:string>Laboratoire de Physiologie Végétale «Nutrition et Métabolisme Azotés» (E 20/C 09), Département des Sciences Biologiques, Faculté des Sciences de Tunis, Campus Universitaire-1060 Tunis, Tunisia</json:string></affiliations></json:item></author><subject><json:item><lang><json:string>eng</json:string></lang><value>Zea mays</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>amino acids</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>cadmium stress</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>glutamate</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>glutathione</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>γ-glutamylcysteine</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>nitrate</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>nitrogen assimilating enzymes</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>proline</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>γ-EC : γ-glutamylcysteine</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>GDH : glutamate dehydrogenase</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>GOGAT : glutamate synthase</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>GS : glutamine synthetase</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>GSH : glutathione</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>NiR : nitrite reductase</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>NR : nitrate reductase</value></json:item></subject><articleId><json:string>80110</json:string></articleId><language><json:string>eng</json:string></language><originalGenre><json:string>Full-length article</json:string></originalGenre><abstract>Summary: Nitrate assimilation in higher plants is the principal biosynthetic pathway leading to glutamate, required for synthesis of particular metabolites that participate in mechanisms of biochemical adaptation to heavy metal stress such as cadmium. Exposure of maize (Zea mays L.) seedlings to increasing cadmium concentrations for 12 days resulted in a significant decrease in nitrate content coupled to inhibition in activities of the enzymes nitrate reductase (EC 1.6.6.1), nitrite reductase (EC 1.6.6.4), glutamine synthetase (EC 6.3.1.2), ferredoxin-glutamate synthase (EC 1.4.7.1), and NADH-glutamate synthase (EC 1.4.1.14). Patterns of NADH- (aminating) and NAD+- (deaminating) glutamate dehydrogenase (EC 1.4.1.2) activities were opposed, with a great increase in the aminating direction. Concurrently, cadmium treatments promoted an increase in protease activity as well as accumulation of ammonia in tissues. These changes in enzyme activities were accompanied by a loss in total amino acids and proteins in both shoots and roots. However, of all amino acids quantified, glutamate, proline, lysine, methionine, and glycine showed a remarkable accumulation in cadmium treated plants, in comparison to control ones. The increased level of glutamate paralleled the elevated contents of γ-glutamylcysteine and glutathione in response to cadmium treatments. The magnitude of changes in all parameters investigated was concentration-dependent. Considered together, metabolite analysis and enzymatic measurements showed that cadmium induces a substantial shift in the operative pathways of ammonia assimilation, and suggested that the induction of NADH-glutamate dehydrogenase activity under cadmium stress may provide glutamate required for enhancing the synthesis of proline, γ-glutamylcysteine and glutathione, which is a common response to cadmium stress conditions. The possible association of these findings with cadmium-binding peptides is discussed.</abstract><qualityIndicators><score>9.75</score><pdfVersion>1.7</pdfVersion><pdfPageSize>568.8 x 792 pts</pdfPageSize><refBibsNative>true</refBibsNative><keywordCount>16</keywordCount><abstractCharCount>1963</abstractCharCount><pdfWordCount>4750</pdfWordCount><pdfCharCount>29704</pdfCharCount><pdfPageCount>8</pdfPageCount><abstractWordCount>264</abstractWordCount></qualityIndicators><title>Cd-Stress on Nitrogen Assimilation</title><pii><json:string>S0176-1617(99)80110-2</json:string></pii><genre><json:string>research-article</json:string></genre><serie><volume>Vol. 16</volume><editor><json:item><name>P.K. Stumpf</name></json:item><json:item><name>E.E. 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Exposure of maize (Zea mays L.) seedlings to increasing cadmium concentrations for 12 days resulted in a significant decrease in nitrate content coupled to inhibition in activities of the enzymes nitrate reductase (EC 1.6.6.1), nitrite reductase (EC 1.6.6.4), glutamine synthetase (EC 6.3.1.2), ferredoxin-glutamate synthase (EC 1.4.7.1), and NADH-glutamate synthase (EC 1.4.1.14). Patterns of NADH- (aminating) and NAD+- (deaminating) glutamate dehydrogenase (EC 1.4.1.2) activities were opposed, with a great increase in the aminating direction. Concurrently, cadmium treatments promoted an increase in protease activity as well as accumulation of ammonia in tissues. These changes in enzyme activities were accompanied by a loss in total amino acids and proteins in both shoots and roots. However, of all amino acids quantified, glutamate, proline, lysine, methionine, and glycine showed a remarkable accumulation in cadmium treated plants, in comparison to control ones. The increased level of glutamate paralleled the elevated contents of γ-glutamylcysteine and glutathione in response to cadmium treatments. The magnitude of changes in all parameters investigated was concentration-dependent. Considered together, metabolite analysis and enzymatic measurements showed that cadmium induces a substantial shift in the operative pathways of ammonia assimilation, and suggested that the induction of NADH-glutamate dehydrogenase activity under cadmium stress may provide glutamate required for enhancing the synthesis of proline, γ-glutamylcysteine and glutathione, which is a common response to cadmium stress conditions. The possible association of these findings with cadmium-binding peptides is discussed.</p></abstract><textClass xml:lang="en"><keywords scheme="keyword"><list><head>Key words</head><item><term>Zea mays</term></item><item><term>amino acids</term></item><item><term>cadmium stress</term></item><item><term>glutamate</term></item><item><term>glutathione</term></item><item><term>γ-glutamylcysteine</term></item><item><term>nitrate</term></item><item><term>nitrogen assimilating enzymes</term></item><item><term>proline</term></item></list></keywords></textClass><textClass xml:lang="en"><keywords scheme="keyword"><list><head>Abbreviations</head><item><term>γ-EC</term><term>γ-glutamylcysteine</term></item><item><term>GDH</term><term>glutamate dehydrogenase</term></item><item><term>GOGAT</term><term>glutamate synthase</term></item><item><term>GS</term><term>glutamine synthetase</term></item><item><term>GSH</term><term>glutathione</term></item><item><term>NiR</term><term>nitrite reductase</term></item><item><term>NR</term><term>nitrate reductase</term></item></list></keywords></textClass></profileDesc><revisionDesc><change when="1999">Published</change></revisionDesc></teiHeader></istex:fulltextTEI><json:item><extension>txt</extension><original>false</original><mimetype>text/plain</mimetype><uri>https://api.istex.fr/document/F3C0073941998680620E4A242C734587C4DCBC27/fulltext/txt</uri></json:item></fulltext><metadata><istex:metadataXml wicri:clean="Elsevier doc found" wicri:toSee="Elsevier, no converted or simple article"><istex:xmlDeclaration>version="1.0" encoding="UTF-8" </istex:xmlDeclaration><istex:docType PUBLIC="-//ES//DTD journal article DTD version 5.1.0//EN//XML" URI="art510.dtd" name="istex:docType"></istex:docType><istex:document><article version="5.1" xml:lang="en" docsubtype="fla"><item-info><jid>JPLPH</jid><aid>80110</aid><ce:pii>S0176-1617(99)80110-2</ce:pii><ce:doi>10.1016/S0176-1617(99)80110-2</ce:doi><ce:copyright type="other" year="1999">Urban & Fischer Verlag</ce:copyright></item-info><head><ce:title>Cd-Stress on Nitrogen Assimilation</ce:title><ce:author-group><ce:author><ce:given-name>N.</ce:given-name><ce:surname>Boussama</ce:surname><ce:cross-ref refid="aff1"><ce:sup>1</ce:sup></ce:cross-ref></ce:author><ce:author><ce:given-name>O.</ce:given-name><ce:surname>Ouariti</ce:surname><ce:cross-ref refid="aff1"><ce:sup>1</ce:sup></ce:cross-ref></ce:author><ce:author><ce:given-name>A.</ce:given-name><ce:surname>Suzuki</ce:surname><ce:cross-ref refid="aff2"><ce:sup>2</ce:sup></ce:cross-ref></ce:author><ce:author><ce:given-name>M.H.</ce:given-name><ce:surname>Ghorbal</ce:surname><ce:cross-ref refid="aff1"><ce:sup>1</ce:sup></ce:cross-ref></ce:author><ce:affiliation id="aff1"><ce:label>1</ce:label><ce:textfn>Laboratoire de Physiologie Végétale «Nutrition et Métabolisme Azotés» (E 20/C 09), Département des Sciences Biologiques, Faculté des Sciences de Tunis, Campus Universitaire-1060 Tunis, Tunisia</ce:textfn></ce:affiliation><ce:affiliation id="aff2"><ce:label>2</ce:label><ce:textfn>Laboratoire du Métabolisme et de la Nutrition des Plantes, INRA, Route de Saint-Cyr, Versailles F-78026 Cedex, France</ce:textfn></ce:affiliation></ce:author-group><ce:date-received day="11" month="9" year="1998"></ce:date-received><ce:date-accepted day="2" month="2" year="1999"></ce:date-accepted><ce:abstract id="ab1" xml:lang="en"><ce:section-title>Summary</ce:section-title><ce:abstract-sec><ce:simple-para id="SP0005">Nitrate assimilation in higher plants is the principal biosynthetic pathway leading to glutamate, required for synthesis of particular metabolites that participate in mechanisms of biochemical adaptation to heavy metal stress such as cadmium. Exposure of maize (<ce:italic>Zea mays</ce:italic> L.) seedlings to increasing cadmium concentrations for 12 days resulted in a significant decrease in nitrate content coupled to inhibition in activities of the enzymes nitrate reductase (EC 1.6.6.1), nitrite reductase (EC 1.6.6.4), glutamine synthetase (EC 6.3.1.2), ferredoxin-glutamate synthase (EC 1.4.7.1), and NADH-glutamate synthase (EC 1.4.1.14). Patterns of NADH- (aminating) and NAD<ce:sup>+</ce:sup>- (deaminating) glutamate dehydrogenase (EC 1.4.1.2) activities were opposed, with a great increase in the aminating direction. Concurrently, cadmium treatments promoted an increase in protease activity as well as accumulation of ammonia in tissues. These changes in enzyme activities were accompanied by a loss in total amino acids and proteins in both shoots and roots. However, of all amino acids quantified, glutamate, proline, lysine, methionine, and glycine showed a remarkable accumulation in cadmium treated plants, in comparison to control ones. The increased level of glutamate paralleled the elevated contents of γ-glutamylcysteine and glutathione in response to cadmium treatments. The magnitude of changes in all parameters investigated was concentration-dependent. Considered together, metabolite analysis and enzymatic measurements showed that cadmium induces a substantial shift in the operative pathways of ammonia assimilation, and suggested that the induction of NADH-glutamate dehydrogenase activity under cadmium stress may provide glutamate required for enhancing the synthesis of proline, γ-glutamylcysteine and glutathione, which is a common response to cadmium stress conditions. The possible association of these findings with cadmium-binding peptides is discussed.</ce:simple-para></ce:abstract-sec></ce:abstract><ce:keywords class="keyword"><ce:section-title>Key words</ce:section-title><ce:keyword><ce:text>Zea mays</ce:text></ce:keyword><ce:keyword><ce:text>amino acids</ce:text></ce:keyword><ce:keyword><ce:text>cadmium stress</ce:text></ce:keyword><ce:keyword><ce:text>glutamate</ce:text></ce:keyword><ce:keyword><ce:text>glutathione</ce:text></ce:keyword><ce:keyword><ce:text>γ-glutamylcysteine</ce:text></ce:keyword><ce:keyword><ce:text>nitrate</ce:text></ce:keyword><ce:keyword><ce:text>nitrogen assimilating enzymes</ce:text></ce:keyword><ce:keyword><ce:text>proline</ce:text></ce:keyword></ce:keywords><ce:keywords class="abr"><ce:section-title>Abbreviations</ce:section-title><ce:keyword><ce:text>γ-EC</ce:text><ce:keyword><ce:text>γ-glutamylcysteine</ce:text></ce:keyword></ce:keyword><ce:keyword><ce:text>GDH</ce:text><ce:keyword><ce:text>glutamate dehydrogenase</ce:text></ce:keyword></ce:keyword><ce:keyword><ce:text>GOGAT</ce:text><ce:keyword><ce:text>glutamate synthase</ce:text></ce:keyword></ce:keyword><ce:keyword><ce:text>GS</ce:text><ce:keyword><ce:text>glutamine synthetase</ce:text></ce:keyword></ce:keyword><ce:keyword><ce:text>GSH</ce:text><ce:keyword><ce:text>glutathione</ce:text></ce:keyword></ce:keyword><ce:keyword><ce:text>NiR</ce:text><ce:keyword><ce:text>nitrite reductase</ce:text></ce:keyword></ce:keyword><ce:keyword><ce:text>NR</ce:text><ce:keyword><ce:text>nitrate reductase</ce:text></ce:keyword></ce:keyword></ce:keywords></head><tail><ce:bibliography id="R0005"><ce:section-title>References</ce:section-title><ce:bibliography-sec id="RS0005"><ce:bib-reference id="bib1"><ce:label>Bradford, 1976</ce:label><sb:reference><sb:contribution><sb:authors><sb:author><ce:given-name>M.M.</ce:given-name><ce:surname>Bradford</ce:surname></sb:author></sb:authors><sb:title><sb:maintitle>A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding</sb:maintitle></sb:title></sb:contribution><sb:host><sb:issue><sb:series><sb:title><sb:maintitle>Anal. 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Exposure of maize (Zea mays L.) seedlings to increasing cadmium concentrations for 12 days resulted in a significant decrease in nitrate content coupled to inhibition in activities of the enzymes nitrate reductase (EC 1.6.6.1), nitrite reductase (EC 1.6.6.4), glutamine synthetase (EC 6.3.1.2), ferredoxin-glutamate synthase (EC 1.4.7.1), and NADH-glutamate synthase (EC 1.4.1.14). Patterns of NADH- (aminating) and NAD+- (deaminating) glutamate dehydrogenase (EC 1.4.1.2) activities were opposed, with a great increase in the aminating direction. Concurrently, cadmium treatments promoted an increase in protease activity as well as accumulation of ammonia in tissues. These changes in enzyme activities were accompanied by a loss in total amino acids and proteins in both shoots and roots. However, of all amino acids quantified, glutamate, proline, lysine, methionine, and glycine showed a remarkable accumulation in cadmium treated plants, in comparison to control ones. The increased level of glutamate paralleled the elevated contents of γ-glutamylcysteine and glutathione in response to cadmium treatments. The magnitude of changes in all parameters investigated was concentration-dependent. Considered together, metabolite analysis and enzymatic measurements showed that cadmium induces a substantial shift in the operative pathways of ammonia assimilation, and suggested that the induction of NADH-glutamate dehydrogenase activity under cadmium stress may provide glutamate required for enhancing the synthesis of proline, γ-glutamylcysteine and glutathione, which is a common response to cadmium stress conditions. The possible association of these findings with cadmium-binding peptides is discussed.</abstract><subject lang="en"><genre>Key words</genre><topic>Zea mays</topic><topic>amino acids</topic><topic>cadmium stress</topic><topic>glutamate</topic><topic>glutathione</topic><topic>γ-glutamylcysteine</topic><topic>nitrate</topic><topic>nitrogen assimilating enzymes</topic><topic>proline</topic></subject><subject lang="en"><genre>Abbreviations</genre><topic>γ-EC : γ-glutamylcysteine</topic><topic>GDH : glutamate dehydrogenase</topic><topic>GOGAT : glutamate synthase</topic><topic>GS : glutamine synthetase</topic><topic>GSH : glutathione</topic><topic>NiR : nitrite reductase</topic><topic>NR : nitrate reductase</topic></subject><relatedItem type="host"><titleInfo><title>Journal of Plant Physiology</title></titleInfo><titleInfo type="abbreviated"><title>JPLPH</title></titleInfo><genre type="journal">journal</genre><originInfo><dateIssued encoding="w3cdtf">199909</dateIssued></originInfo><identifier type="ISSN">0176-1617</identifier><identifier type="PII">S0176-1617(99)X8108-9</identifier><part><date>199909</date><detail type="volume"><number>155</number><caption>vol.</caption></detail><detail type="issue"><number>3</number><caption>no.</caption></detail><extent unit="issue pages"><start>297</start><end>440</end></extent><extent unit="pages"><start>310</start><end>317</end></extent></part></relatedItem><identifier type="istex">F3C0073941998680620E4A242C734587C4DCBC27</identifier><identifier type="DOI">10.1016/S0176-1617(99)80110-2</identifier><identifier type="PII">S0176-1617(99)80110-2</identifier><identifier type="ArticleID">80110</identifier><accessCondition type="use and reproduction" contentType="copyright">©1999 Urban & Fischer Verlag</accessCondition><recordInfo><recordContentSource>ELSEVIER</recordContentSource><recordOrigin>Urban & Fischer Verlag, ©1999</recordOrigin></recordInfo></mods></metadata></istex></record>Pour manipuler ce document sous Unix (Dilib)
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