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Research Paper

Regulation of Nitrate Transport in Citrus Rootstocks Depending of Nitrogen Availability

Miguel Cerezo, Gemma Camañes, Victor Flors, Eduardo Primo-Millo and Pilar García-Agustín

volume 2 | issue 5

september/october
Pages: 337 - 342

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Previously, we reported that in Citrus plants, nitrate influx through the plasmalemma of roots cells follows a biphasic pattern, suggesting the existence of at least two different uptake systems, a high and low affinity transport system (HATS and LATS, respectively). Here, we describe a novel inducible high affinity transport system (iHATS). This new nitrate transport system has a high capacity to uptake nitrate in two different Citrus rootstocks (Cleopatra mandarin and Troyer citrange). The iHATS was saturable, showing higher affinity than constitutive high affinity transport system (cHATS) to the substrate NO3-. The Vmax for this saturable component iHATS was higher than cHATS, reaching similar values in both rootstocks.

Additionally, we studied the regulation of root NO3- uptake mediated by both HATS (iHATS and cHATS) and LATS. In both rootstocks, cHATS is constitutive and independent of N-status. Concerning the regulation of iHATS, this system is up-regulated by NO3- and down-regulated by the N status and by NO3- itself when plants are exposed to it for a longer period of time. LATS in Cleopatra mandarin and Troyer citrange rootstocks is repressed by the N-status.

The use of various metabolic uncouplers or inhibitors indicated that NO3- net uptake mediated by iHATS and LATS was an active transport system in both rootstocks.

Authors

Miguel Cerezo

Universitat Jaume I; Castellón, Spain

Gemma Camañes

Universitat Jaume I; Castellón, Spain

Victor Flors

University of Jaume; Castellón, Spain

Eduardo Primo-Millo

Instituto Valenciano de Investigaciones Agrarias; Moncada, Spain

Pilar García-Agustín