Medicago truncatula Zinc‐Iron Permease6 provides zinc to rhizobia‐infected nodule cells

Zinc is a micronutrient required for symbiotic nitrogen fixation. It has been proposed that in model legume Medicago truncatula, zinc is delivered by the root vasculature into the nodule and released in the infection/differentiation zone. There, transporters must introduce this element into rhizobia...

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Published in:Plant, cell and environment cell and environment, 2017-11, Vol.40 (11), p.2706-2719
Main Authors: Abreu, Isidro, Saéz, Ángela, Castro‐Rodríguez, Rosario, Escudero, Viviana, Rodríguez‐Haas, Benjamín, Senovilla, Marta, Larue, Camille, Grolimund, Daniel, Tejada‐Jiménez, Manuel, Imperial, Juan, González‐Guerrero, Manuel
Format: Article
Language:English
Subjects:
Alfalfa
Cell Differentiation
Cell Membrane - metabolism
Cytosol
Differentiation
Environmental Sciences
Gene Expression Regulation, Plant
Heavy metals
Homeostasis
Host plants
Infections
Iron
Legumes
Life Sciences
Medicago truncatula
Medicago truncatula - enzymology
Medicago truncatula - genetics
Medicago truncatula - microbiology
Models, Biological
Nitrogen
Nitrogen fixation
Nitrogenase
nodule
Nodules
Nutrients
Permease
Phenotype
Plant Proteins - genetics
Plant Proteins - metabolism
Rhizobium - physiology
RNA Interference
RNA-mediated interference
Root nodules
Root Nodules, Plant - cytology
Root Nodules, Plant - enzymology
Root Nodules, Plant - genetics
Subcellular Fractions - metabolism
symbiotic nitrogen fixation
Transition metals
Vegetal Biology
Zinc
Zinc - metabolism
Zinc‐Iron Permease
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Summary:Zinc is a micronutrient required for symbiotic nitrogen fixation. It has been proposed that in model legume Medicago truncatula, zinc is delivered by the root vasculature into the nodule and released in the infection/differentiation zone. There, transporters must introduce this element into rhizobia‐infected cells to metallate the apoproteins that use zinc as a cofactor. MtZIP6 (Medtr4g083570) is an M. truncatula Zinc‐Iron Permease (ZIP) that is expressed only in roots and nodules, with the highest expression levels in the infection/differentiation zone. Immunolocalization studies indicate that it is located in the plasma membrane of nodule rhizobia‐infected cells. Down‐regulating MtZIP6 expression levels with RNAi does not result in any strong phenotype when plants are fed mineral nitrogen. However, these plants displayed severe growth defects when they depended on nitrogen fixed by their nodules, losing of 80% of their nitrogenase activity. The reduction of this activity was likely an indirect effect of zinc being retained in the infection/differentiation zone and not reaching the cytosol of rhizobia‐infected cells. These data are consistent with a model in which MtZIP6 would be responsible for zinc uptake by rhizobia‐infected nodule cells in the infection/differentiation zone. Symbiotic nitrogen fixation carried out in legume nodules requires relatively large levels of essential transition metals. These nutrients have to be provided by the host plant through dedicated metal transporters. Here, we have determined the role of MtZIP6 in providing zinc to rhizobia‐infected cells in Medicago truncatula nodules and shown that efficient zinc supply is required for nodule nitrogenase activity.
ISSN:0140-7791
1365-3040
DOI:10.1111/pce.13035