Characterization and regulation of ammonium transport systems in Citrus plants.
Identifieur interne : 000043 ( Ncbi/Checkpoint ); précédent : 000042; suivant : 000044Characterization and regulation of ammonium transport systems in Citrus plants.
Auteurs : M. Cerezo [Espagne] ; P. Tillard ; A. Gojon ; E. Primo-Millo ; P. García-AgustínSource :
- Planta [ 0032-0935 ] ; 2001.
English descriptors
- KwdEn :
- Biological Transport (physiology), Citrus (physiology), Down-Regulation, Hydrogen-Ion Concentration, Hydroponics, Ionophores, Kinetics, Nitrogen Isotopes, Plant Roots (physiology), Proton-Translocating ATPases (antagonists & inhibitors), Quaternary Ammonium Compounds (administration & dosage), Quaternary Ammonium Compounds (antagonists & inhibitors), Quaternary Ammonium Compounds (metabolism), Up-Regulation.
- MESH :
- chemical , administration & dosage : Quaternary Ammonium Compounds.
- chemical , antagonists & inhibitors : Proton-Translocating ATPases, Quaternary Ammonium Compounds.
- chemical , metabolism : Quaternary Ammonium Compounds.
- chemical : Ionophores, Nitrogen Isotopes.
- physiology : Biological Transport, Citrus, Plant Roots.
- Down-Regulation, Hydrogen-Ion Concentration, Hydroponics, Kinetics, Up-Regulation.
Abstract
We have investigated both the kinetics and regulation of 15NH4+ influx in roots of 3-month-old hydroponically grown Citrus (Citrus sinensis L. Osbeck x Poncirus trifoliata Blanco) seedlings. The 15NH4+ influx is saturable below an external ammonium concentration of 1 mM, indicating the action of a high-affinity transport system (HATS). The HATS is under feedback repression by the N status of the plant, being down-regulated in plants adequately supplied with N during growth, and up-regulated by N-starvation. When assayed between 1 and 50 mM [15NH4+]0, the 15NH4+ influx showed a linear response typical of a low-affinity transport system (LATS). The activity of the LATS increased in plants supplied with NH4+ as compared with plants grown on an N-free medium. Transfer of the plants to N-free solution resulted in a marked decrease in the LATS-mediated 15NH4+ influx. Accordingly, resupply of NH4+ after N-starvation triggered a dramatic stimulation of the activity of the LATS. These data provide evidence that in Citrus plants, the LATS or at least one of its components is inducible by NH4+. Even when up-regulated, both the HATS and the LATS displayed a limited capacity, as compared with that usually found in herbaceous species. The use of various metabolic uncouplers or inhibitors indicated that 15NH4+ influx mediated by the HATS is strongly dependent on energy metabolism and H+ transmembrane electrochemical gradient. By contrast, the LATS is not affected by protonophores or inhibitors of the H(+)-ATPase, suggesting that its activity is mostly driven by the NH4+/NH3 transmembrane gradient. In agreement with these hypotheses, the HATS-mediated 15NH4+ influx was strongly inhibited when the solution pH was raised from 4 to 7, whereas influx mediated by the LATS was slightly stimulated.
PubMed: 11762176
Affiliations:
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Tillard</name></author><author><name sortKey="Gojon, A" sort="Gojon, A" uniqKey="Gojon A" first="A" last="Gojon">A. Gojon</name></author><author><name sortKey="Primo Millo, E" sort="Primo Millo, E" uniqKey="Primo Millo E" first="E" last="Primo-Millo">E. Primo-Millo</name></author><author><name sortKey="Garcia Agustin, P" sort="Garcia Agustin, P" uniqKey="Garcia Agustin P" first="P" last="García-Agustín">P. García-Agustín</name></author></titleStmt><publicationStmt><idno type="wicri:source">PubMed</idno><date when="2001">2001</date><idno type="RBID">pubmed:11762176</idno><idno type="pmid">11762176</idno><idno type="wicri:Area/PubMed/Corpus">000E86</idno><idno type="wicri:Area/PubMed/Curation">000E86</idno><idno type="wicri:Area/PubMed/Checkpoint">000E86</idno><idno type="wicri:Area/Ncbi/Merge">000043</idno><idno type="wicri:Area/Ncbi/Curation">000043</idno><idno type="wicri:Area/Ncbi/Checkpoint">000043</idno></publicationStmt><sourceDesc><biblStruct><analytic><title xml:lang="en">Characterization and regulation of ammonium transport systems in Citrus plants.</title><author><name sortKey="Cerezo, M" sort="Cerezo, M" uniqKey="Cerezo M" first="M" last="Cerezo">M. Cerezo</name><affiliation wicri:level="2"><nlm:affiliation>Unidad de Fisiología Vegetal, Departamento de Ciencias Experimentales, Escuela Superior de Tecnologia y Ciencias Experimentales, Universitat Jaume I, 12071 Castellón, Spain.</nlm:affiliation><country xml:lang="fr">Espagne</country><wicri:regionArea>Unidad de Fisiología Vegetal, Departamento de Ciencias Experimentales, Escuela Superior de Tecnologia y Ciencias Experimentales, Universitat Jaume I, 12071 Castellón</wicri:regionArea><placeName><region nuts="2" type="communauté">Communauté valencienne</region></placeName></affiliation></author><author><name sortKey="Tillard, P" sort="Tillard, P" uniqKey="Tillard P" first="P" last="Tillard">P. Tillard</name></author><author><name sortKey="Gojon, A" sort="Gojon, A" uniqKey="Gojon A" first="A" last="Gojon">A. Gojon</name></author><author><name sortKey="Primo Millo, E" sort="Primo Millo, E" uniqKey="Primo Millo E" first="E" last="Primo-Millo">E. Primo-Millo</name></author><author><name sortKey="Garcia Agustin, P" sort="Garcia Agustin, P" uniqKey="Garcia Agustin P" first="P" last="García-Agustín">P. García-Agustín</name></author></analytic><series><title level="j">Planta</title><idno type="ISSN">0032-0935</idno><imprint><date when="2001" type="published">2001</date></imprint></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass><keywords scheme="KwdEn" xml:lang="en"><term>Biological Transport (physiology)</term><term>Citrus (physiology)</term><term>Down-Regulation</term><term>Hydrogen-Ion Concentration</term><term>Hydroponics</term><term>Ionophores</term><term>Kinetics</term><term>Nitrogen Isotopes</term><term>Plant Roots (physiology)</term><term>Proton-Translocating ATPases (antagonists & inhibitors)</term><term>Quaternary Ammonium Compounds (administration & dosage)</term><term>Quaternary Ammonium Compounds (antagonists & inhibitors)</term><term>Quaternary Ammonium Compounds (metabolism)</term><term>Up-Regulation</term></keywords><keywords scheme="MESH" type="chemical" qualifier="administration & dosage" xml:lang="en"><term>Quaternary Ammonium Compounds</term></keywords><keywords scheme="MESH" type="chemical" qualifier="antagonists & inhibitors" xml:lang="en"><term>Proton-Translocating ATPases</term><term>Quaternary Ammonium Compounds</term></keywords><keywords scheme="MESH" type="chemical" qualifier="metabolism" xml:lang="en"><term>Quaternary Ammonium Compounds</term></keywords><keywords scheme="MESH" type="chemical" xml:lang="en"><term>Ionophores</term><term>Nitrogen Isotopes</term></keywords><keywords scheme="MESH" qualifier="physiology" xml:lang="en"><term>Biological Transport</term><term>Citrus</term><term>Plant Roots</term></keywords><keywords scheme="MESH" xml:lang="en"><term>Down-Regulation</term><term>Hydrogen-Ion Concentration</term><term>Hydroponics</term><term>Kinetics</term><term>Up-Regulation</term></keywords></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">We have investigated both the kinetics and regulation of 15NH4+ influx in roots of 3-month-old hydroponically grown Citrus (Citrus sinensis L. Osbeck x Poncirus trifoliata Blanco) seedlings. The 15NH4+ influx is saturable below an external ammonium concentration of 1 mM, indicating the action of a high-affinity transport system (HATS). The HATS is under feedback repression by the N status of the plant, being down-regulated in plants adequately supplied with N during growth, and up-regulated by N-starvation. When assayed between 1 and 50 mM [15NH4+]0, the 15NH4+ influx showed a linear response typical of a low-affinity transport system (LATS). The activity of the LATS increased in plants supplied with NH4+ as compared with plants grown on an N-free medium. Transfer of the plants to N-free solution resulted in a marked decrease in the LATS-mediated 15NH4+ influx. Accordingly, resupply of NH4+ after N-starvation triggered a dramatic stimulation of the activity of the LATS. These data provide evidence that in Citrus plants, the LATS or at least one of its components is inducible by NH4+. Even when up-regulated, both the HATS and the LATS displayed a limited capacity, as compared with that usually found in herbaceous species. The use of various metabolic uncouplers or inhibitors indicated that 15NH4+ influx mediated by the HATS is strongly dependent on energy metabolism and H+ transmembrane electrochemical gradient. By contrast, the LATS is not affected by protonophores or inhibitors of the H(+)-ATPase, suggesting that its activity is mostly driven by the NH4+/NH3 transmembrane gradient. In agreement with these hypotheses, the HATS-mediated 15NH4+ influx was strongly inhibited when the solution pH was raised from 4 to 7, whereas influx mediated by the LATS was slightly stimulated.</div></front></TEI><affiliations><list><country><li>Espagne</li></country><region><li>Communauté valencienne</li></region></list><tree><noCountry><name sortKey="Garcia Agustin, P" sort="Garcia Agustin, P" uniqKey="Garcia Agustin P" first="P" last="García-Agustín">P. García-Agustín</name><name sortKey="Gojon, A" sort="Gojon, A" uniqKey="Gojon A" first="A" last="Gojon">A. Gojon</name><name sortKey="Primo Millo, E" sort="Primo Millo, E" uniqKey="Primo Millo E" first="E" last="Primo-Millo">E. Primo-Millo</name><name sortKey="Tillard, P" sort="Tillard, P" uniqKey="Tillard P" first="P" last="Tillard">P. Tillard</name></noCountry><country name="Espagne"><region name="Communauté valencienne"><name sortKey="Cerezo, M" sort="Cerezo, M" uniqKey="Cerezo M" first="M" last="Cerezo">M. Cerezo</name></region></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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