Ammonium transport and CitAMT1 expression are regulated by N in Citrus plants
2008
Camañes, Gemma | Cerezo García, Miguel | Primo Millo, Eduardo | Gojon, Alain | García Agustín, Pilar
Citrus seedlings (Citrus sinensis L. Osbeck × Poncirus trifoliata Blanco) were used to describe the effects of different N treatments on the NH4 + influx mediated by high- and low-affinity transport systems (HATS and LATS, respectively) and CitAMT1 gene expression. Results show that Citrus plants favor NH4 + over NO3 − influx mediated by HATS and LATS when both N sources are present in the nutrient solution and Citrus plants display a much higher capacity to take up NH4 + than NO3 −. Furthermore, NH4 + exerts a regulatory effect on NH4 + HATS activity and CitAMT1 expression, both are down-regulated by high N status of the plant, but specifically stimulated by NH4 + and the balance between these two opposite effects depends on the prior nutrition regime of the plant. On the other hand, supply of NO3 − inhibitsCitAMT1 expression but doesn’t affect NH4 + HATS activity on the roots. To explain this discrepancy, it is possible that other CitAMT1 transporters, up-regulated by N limitation, but not repressed by NO3 − could be involved in the stimulation of NH4 + HATS activity under pure NO3 − nutrition or CitAMT1 transporter could be regulated at the post-transcriptional level
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