title: Tissue-specific down-regulation of LjAMT1;1 compromises nodule function and enhances nodulation in Lotus japonicus.
abstract: Plant ammonium transporters of the AMT1 family are involved in N-uptake from the soil and ammonium transport, and recycling within the plant. Although AMT1 genes are known to be expressed in nitrogen-fixing nodules of legumes, their precise roles in this specialized organ remain unknown. We have taken a reverse-genetic approach to decipher the physiological role of LjAMT1;1 in Lotus japonicus nodules. LjAMT1;1 is normally expressed in both the infected zone and the vascular tissue of Lotus nodules. Inhibition of LjAMT1;1 gene expression, using an antisense gene construct driven by a leghemoglobin promoter resulted in a substantial reduction of LjAMT1;1 transcript in the infected tissue but not the vascular bundles of transgenic plants. As a result, the nitrogen-fixing activity of nodules was partially impaired and nodule number increased compared to control plants. Expression of LjAMT1;1-GFP fusion protein in plant cells indicated a plasma-membrane location for the LjAMT1;1 protein. Taken together, the results are consistent with a role of LjAMT1;1 in retaining ammonium derived from symbiotic nitrogen fixation in plant cells prior to its assimilation.
authors.affiliation: Institute of Genetics and Biophysics A. Buzzati Traverso, Via P. Castellino 12, 80131, Napoli, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Rogato
authors.forename: Enrica
authors.initials: E
authors.lastname: D'Apuzzo
authors.forename: Ani
authors.initials: A
authors.lastname: Barbulova
authors.forename: Selim
authors.initials: S
authors.lastname: Omrane
authors.forename: Catalina
authors.initials: C
authors.lastname: Stedel
authors.forename: Ulrike
authors.initials: U
authors.lastname: Simon-Rosin
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Katinakis
authors.forename: Manolis
authors.initials: M
authors.lastname: Flemetakis
authors.forename: Michael
authors.initials: M
authors.lastname: Udvardi
authors.forename: Maurizio
authors.initials: M
authors.lastname: Chiurazzi
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D015536:Down-Regulation; D017403:In Situ Hybridization; D000070116:Lotus / Q000502:physiology*; D009586:Nitrogen Fixation / Q000502:physiology*; D010940:Plant Proteins / Q000502:physiology*; D030821:Plants, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D010940:Plant Proteins
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