Journal Article

Medicago truncatula Molybdate Transporter type 1 (MtMOT1.3) is a plasma membrane molybdenum transporter required for nitrogenase activity in root nodules under molybdenum deficiency

Patricia Gil-Díez, Kirankumar S. Mysore, Jiangqi Wen, Manuel Tejada-Jiménez, Juan Imperial, Javier León-Mediavilla, Manuel González-Guerrero

2017

Overview

Molybdenum, as a component of the iron-molybdenum cofactor of nitrogenase, is essential for symbiotic nitrogen fixation. This nutrient has to be provided by the host plant through molybdate transporters. Members of the molybdate transporter family Molybdate Transporter type 1 (MOT1) were identified in the model legume Medicago truncatula and their expression in nodules was determined. Yeast toxicity assays, confocal microscopy, and phenotypical characterization of a Transposable Element from Nicotiana tabacum (Tnt1) insertional mutant line were carried out in the one M. truncatula MOT1 family member specifically expressed in nodules. Among the five MOT1 members present in the M. truncatula genome, MtMOT1.3 is the only one uniquely expressed in nodules. MtMOT1.3 shows molybdate transport capabilities when expressed in yeast. Immunolocalization studies revealed that MtMOT1.3 is located in the plasma membrane of nodule cells. A mot1.3-1 knockout mutant showed impaired growth concomitant with a reduction of nitrogenase activity. This phenotype was rescued by increasing molybdate concentrations in the nutritive solution, or upon addition of an assimilable nitrogen source. Furthermore, mot1.3-1 plants transformed with a functional copy of MtMOT1.3 showed a wild-type-like phenotype. These data are consistent with a model in which MtMOT1.3 is responsible for introducing molybdate into nodule cells, which is later used to synthesize functional nitrogenase.

• Publisher: New Phytologist Trust,Wiley Subscription Services, Inc
• Subject: Alfalfa / Anion Transport Proteins - metabolism / Cells / Confocal microscopy / enzyme activity / genome / Genomes / Host plants / legumes / Medicago truncatula / Medicago truncatula - metabolism / metal transport / Microscopy / Mineral nutrients / Molybdate / molybdate transport / molybdates / Molybdenum / Molybdenum - metabolism / mutants / Nicotiana tabacum / Nitrogen / Nitrogen fixation / Nitrogenase / Nitrogenase - metabolism / Nodules / nutrient solutions / phenotype / Phenotypes / Plant Proteins - metabolism / plasma membrane / Root nodules / Root Nodules, Plant - metabolism / Symbionts / symbiotic nitrogen fixation / Toxicity / transporters / Transposons / Yeast / Yeasts