title: Functional assessment of the Medicago truncatula NIP/LATD protein demonstrates that it is a high-affinity nitrate transporter.
abstract: The Medicago truncatula NIP/LATD (for Numerous Infections and Polyphenolics/Lateral root-organ Defective) gene encodes a protein found in a clade of nitrate transporters within the large NRT1(PTR) family that also encodes transporters of dipeptides and tripeptides, dicarboxylates, auxin, and abscisic acid. Of the NRT1(PTR) members known to transport nitrate, most are low-affinity transporters. Here, we show that M. truncatula nip/latd mutants are more defective in their lateral root responses to nitrate provided at low (250 μm) concentrations than at higher (5 mm) concentrations; however, nitrate uptake experiments showed no discernible differences in uptake in the mutants. Heterologous expression experiments showed that MtNIP/LATD encodes a nitrate transporter: expression in Xenopus laevis oocytes conferred upon the oocytes the ability to take up nitrate from the medium with high affinity, and expression of MtNIP/LATD in an Arabidopsis chl1(nrt1.1) mutant rescued the chlorate susceptibility phenotype. X. laevis oocytes expressing mutant Mtnip-1 and Mtlatd were unable to take up nitrate from the medium, but oocytes expressing the less severe Mtnip-3 allele were proficient in nitrate transport. M. truncatula nip/latd mutants have pleiotropic defects in nodulation and root architecture. Expression of the Arabidopsis NRT1.1 gene in mutant Mtnip-1 roots partially rescued Mtnip-1 for root architecture defects but not for nodulation defects. This suggests that the spectrum of activities inherent in AtNRT1.1 is different from that possessed by MtNIP/LATD, but it could also reflect stability differences of each protein in M. truncatula. Collectively, the data show that MtNIP/LATD is a high-affinity nitrate transporter and suggest that it could have another function.
authors.affiliation: Department of Biological Sciences, University of North Texas, Denton, Texas 76203, USA.
authors.forename: Rammyani
authors.initials: R
authors.lastname: Bagchi
authors.forename: Mohammad
authors.initials: M
authors.lastname: Salehin
authors.forename: O Sarah
authors.initials: OS
authors.lastname: Adeyemo
authors.forename: Carolina
authors.initials: C
authors.lastname: Salazar
authors.forename: Vladimir
authors.initials: V
authors.lastname: Shulaev
authors.forename: D Janine
authors.initials: DJ
authors.lastname: Sherrier
authors.forename: Rebecca
authors.initials: R
authors.lastname: Dickstein
mesh_terms: D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000378:metabolism; D000483:Alleles; D000818:Animals; D027321:Anion Transport Proteins / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D001692:Biological Transport; D002704:Chlorates / Q000378:metabolism / Q000494:pharmacology; D017343:Genes, Plant; D005816:Genetic Complementation Test; D046913:Medicago truncatula / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D000091285:Nitrate Transporters; D009566:Nitrates / Q000378:metabolism* / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D055170:Plant Root Nodulation; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology; D017680:Potassium Compounds / Q000494:pharmacology; D055550:Protein Stability; D016962:Sinorhizobium meliloti / Q000254:growth & development; D013559:Symbiosis; D053719:Tandem Mass Spectrometry; D014170:Transformation, Genetic; D014982:Xenopus laevis / Q000235:genetics / Q000378:metabolism
chemical_list: D027321:Anion Transport Proteins; D002704:Chlorates; C101492:NRT1.1 protein, Arabidopsis; D000091285:Nitrate Transporters; D009566:Nitrates; D010940:Plant Proteins; D017680:Potassium Compounds; C023844:potassium nitrate; C006568:ammonium nitrate