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Descripción
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| Symbiotic nitrogen fixation (SNF) between legumes and rhizobia lead to the development of new organs, the root nodules. Although nodules represent less than 5% of the plant biomass, it contains up to 60% of the iron and 30% of the zinc content. This implies an important trafficking of metals to nitrogen fixing organs, although it currently remains unknown how they are delivered (1). It has been proposed that zinc should be transported through vascular bundles to the aposplast of the apical zone of the nodule, where a zinc transporter located at the plasma membrane of infected cells would mediate the acquisition of zinc (1), as previously described for iron through MtNRAMP1 (2, 3). MtZIP6 was previously described as a Zn transporter. Using qPCR and a GUS transcriptional reporter line we found that MtZIP6 is highly expressed in nodules, spatially restricted to the zone where bacteria differentiates into bacteroid, and at a minor extent also in roots. MtZIP6 is located in the plasma membrane of rhizobia-infected cells, as determined by fusing to MtZIP6 a C-terminus 3xHA tag. To determine the role of MtZIP6 we transformed M. truncatula plants with a MtZIP6 RNAi construction resulting in an average 80% reduction of MtZIP6 expression. mtzip6 RNAi plants showed no significant differences under non-symbiotic conditions. In contrast, mtzip6 RNAi plants inoculated with S. meliloti 2011 showed a significant reduction in nitrogenase activity, accompanied by a decrease in plant growth. To further characterize the phenotype of MtZIP6 in planta we analyzed both content and distribution of transition metals in control and silenced plants using Zinpyr1 Zn probe and Synchrotron-X Ray Fluorescence. Zinc was accumulated at the apical zone of the nodule and reduced in nitrogen-fixing cells in mtzip6 RNAi plants, suggesting that MtZIP6 participates in Zn homeostasis. Our results support a model in which MtZIP6 would be mediating the acquisition of Zn by rhizobia-infected cells. Its absence would lead to an accumulation of Zn in the apoplast of the apical regions of the nodule, and an impairment of nitrogen fixation due to the lack of a still-unknown essential zinc-metalloprotein. | |
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Internacional
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Si |
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Nombre congreso
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International Nitrogen Fixation Conference |
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Tipo de participación
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970 |
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Lugar del congreso
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Granada |
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Revisores
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Si |
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ISBN o ISSN
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0000000000 |
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DOI
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Fecha inicio congreso
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03/09/2017 |
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Fecha fin congreso
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07/09/2017 |
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Desde la página
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153 |
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Hasta la página
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153 |
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Título de las actas
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International Nitrogen Fixation Conference |