Functional Assessment of the Medicago truncatula NIP/LATD Protein Demonstrates That It Is a High-Affinity Nitrate Transporter Bagchi, Rammyani Salehin, Mohammad Adeyemo, O. Sarah Salazar, Carolina Shulaev, Vladimir Sherrier, D. Janine Dickstein, Rebecca American Society of Plant Biologists 2012-10 English This article discusses a functional assessment of the Medicago truncatula NIP/LATD. 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, the authors show that M. truncatula nip/latd mutants are more defective in their lateral root responses to nitrate provided at low (250 μм) concentrations than at higher (5mм) 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, 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 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. genes proteins medicago truncatula nitrogen Plant Physiology, 2012, Rockville: American Society of Plant Biologists, pp. 906-916 Public Article 11 p. Text doi: 10.1104/pp.112.196444 http://digital.library.unt.edu/ark:/67531/metadc130185/ ark: ark:/67531/metadc130185