Characterization and regulation of ammonium transport systems in Citrus plants
We have investigated both the kinetics and regulation of (NH4+)-N-15 influx in roots of 3-month-old hydroponically grown Citrus (Citrus sinensis L. Osbeck x Poncirus trifoliata Blanco) seedlings. The (NH4+)-N-15 influx is saturable below an external ammonium concentration of 1 mM, indicating the act...
| Main Authors: | , , , , |
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| Format: | Artículo |
| Language: | Inglés |
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2017
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| Online Access: | http://hdl.handle.net/20.500.11939/5003 |
| _version_ | 1855491849961078784 |
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| author | Cerezo, Miguel Tillard, P. Gojon, Alain Primo-Millo, Eduardo Garcia-Agustin, P. |
| author_browse | Cerezo, Miguel Garcia-Agustin, P. Gojon, Alain Primo-Millo, Eduardo Tillard, P. |
| author_facet | Cerezo, Miguel Tillard, P. Gojon, Alain Primo-Millo, Eduardo Garcia-Agustin, P. |
| author_sort | Cerezo, Miguel |
| collection | ReDivia |
| description | We have investigated both the kinetics and regulation of (NH4+)-N-15 influx in roots of 3-month-old hydroponically grown Citrus (Citrus sinensis L. Osbeck x Poncirus trifoliata Blanco) seedlings. The (NH4+)-N-15 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 downregulated in plants adequately supplied with N during growth, and up-regulated by N-starvation. When assayed between 1 and 50 mM [(NH4+)-N-15](0), the (NH4+)-N-15 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 (NH4+)-N-15 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 (NH4+)-N-15 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 (NH4+)-N-15 influx was strongly inhibited when the solution pH was raised from 4 to 7, whereas influx mediated by the LATS was slightly stimulated. |
| format | Artículo |
| id | ReDivia5003 |
| institution | Instituto Valenciano de Investigaciones Agrarias (IVIA) |
| language | Inglés |
| publishDate | 2017 |
| publishDateRange | 2017 |
| publishDateSort | 2017 |
| record_format | dspace |
| spelling | ReDivia50032025-04-25T14:45:07Z Characterization and regulation of ammonium transport systems in Citrus plants Cerezo, Miguel Tillard, P. Gojon, Alain Primo-Millo, Eduardo Garcia-Agustin, P. We have investigated both the kinetics and regulation of (NH4+)-N-15 influx in roots of 3-month-old hydroponically grown Citrus (Citrus sinensis L. Osbeck x Poncirus trifoliata Blanco) seedlings. The (NH4+)-N-15 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 downregulated in plants adequately supplied with N during growth, and up-regulated by N-starvation. When assayed between 1 and 50 mM [(NH4+)-N-15](0), the (NH4+)-N-15 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 (NH4+)-N-15 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 (NH4+)-N-15 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 (NH4+)-N-15 influx was strongly inhibited when the solution pH was raised from 4 to 7, whereas influx mediated by the LATS was slightly stimulated. 2017-06-01T10:11:32Z 2017-06-01T10:11:32Z 2001 NOV 2001 article Cerezo, M., Tillard, P., Gojon, A., Primo-Millo, E., Garcia-Agustin, P. (2001). Characterization and regulation of ammonium transport systems in Citrus plants. Planta, 214(1), 97-105. 0032-0935 http://hdl.handle.net/20.500.11939/5003 10.1007/s004250100590 en openAccess Impreso |
| spellingShingle | Cerezo, Miguel Tillard, P. Gojon, Alain Primo-Millo, Eduardo Garcia-Agustin, P. Characterization and regulation of ammonium transport systems in Citrus plants |
| title | Characterization and regulation of ammonium transport systems in Citrus plants |
| title_full | Characterization and regulation of ammonium transport systems in Citrus plants |
| title_fullStr | Characterization and regulation of ammonium transport systems in Citrus plants |
| title_full_unstemmed | Characterization and regulation of ammonium transport systems in Citrus plants |
| title_short | Characterization and regulation of ammonium transport systems in Citrus plants |
| title_sort | characterization and regulation of ammonium transport systems in citrus plants |
| url | http://hdl.handle.net/20.500.11939/5003 |
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