title: Morphological and genetic changes induced by excess Zn in roots of Medicago truncatula A17 and a Zn accumulating mutant.
abstract: BACKGROUND
  Nutrient fluxes associated with legume-rhizobia symbioses are poorly understood and little is known regarding the influence of abiotic stresses on development and maintenance of N-fixing nodules and root system architecture (RSA). We examined effects of Zn on nodule development and structure, root architecture, and expression of nodulation-related miRNAs in Medicago truncatula and the mutant, raz (requires additional Zn).
  
  
  RESULTS
  Excess Zn increased root and shoot associated Zn in both genotypes, however, raz plants had lower root associated Zn than WT plants. Roots of raz plants exposed to excess Zn had less volume, surface area, and total length compared to WT plants. Raz plants had lower lateral root number than WT plants. Excess Zn was found to increase root diameter in both genotypes. The Mn Translocation Factor (TfMn) increased in response to Zn in both genotypes; this was more pronounced in raz plants. TfZn was higher in raz plants and reduced in both genotypes in response to Zn. Nodulation was not influenced by Zn treatment or plant genotype. MicroRNA166 was upregulated under excess Zn in WT plants.
  
  
  CONCLUSIONS
  Neither the raz mutation nor Zn treatment affected nodulation, however, raz plants had altered RSA compared with WT and responded differently to Zn, implying the mutation potentially modulates RSA responses to Zn but doesn't play a direct role in nodulation. MicroRNA166 was significantly induced in WT plants by excess Zn, warranting further investigation into the potential role it plays in controlling RSA.
authors.affiliation: Rhizosphere Science Laboratory, Department of Plant and Soil Science, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: Ricky W
authors.initials: RW
authors.lastname: Lewis
authors.forename: Guiliang
authors.initials: G
authors.lastname: Tang
authors.forename: David H
authors.initials: DH
authors.lastname: McNear
mesh_terms: D002413:Cations, Divalent; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005838:Genotype; D046913:Medicago truncatula / Q000033:anatomy & histology / Q000187:drug effects* / Q000235:genetics; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D010937:Plant Growth Regulators / Q000378:metabolism* / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D055170:Plant Root Nodulation / Q000187:drug effects* / Q000235:genetics; D012231:Rhizobium / Q000254:growth & development; D053204:Root Nodules, Plant / Q000033:anatomy & histology / Q000187:drug effects* / Q000235:genetics; D016962:Sinorhizobium meliloti / Q000254:growth & development; D013559:Symbiosis; D015032:Zinc / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D002413:Cations, Divalent; D035683:MicroRNAs; D010937:Plant Growth Regulators; D010940:Plant Proteins; D015032:Zinc