title: Elevated CO(2) modifies N acquisition of Medicago truncatula by enhancing N fixation and reducing nitrate uptake from soil.
abstract: The effects of elevated CO2 (750 ppm vs. 390 ppm) were evaluated on nitrogen (N) acquisition and assimilation by three Medicago truncatula genotypes, including two N-fixing-deficient mutants (dnf1-1 and dnf1-2) and their wild-type (Jemalong). The proportion of N acquisition from atmosphere and soil were quantified by (15)N stable isotope, and N transportation and assimilation-related genes and enzymes were determined by qPCR and biochemical analysis. Elevated CO2 decreased nitrate uptake from soil in all three plant genotypes by down-regulating nitrate reductase (NR), nitrate transporter NRT1.1 and NR activity. Jemalong plant, however, produced more nodules, up-regulated N-fixation-related genes and enhanced percentage of N derived from fixation (%Ndf) to increase foliar N concentration and N content in whole plant (Ntotal Yield) to satisfy the requirement of larger biomass under elevated CO2. In contrast, both dnf1 mutants deficient in N fixation consequently decreased activity of glutamine synthetase/glutamate synthase (GS/GOGAT) and N concentration under elevated CO2. Our results suggest that elevated CO2 is likely to modify N acquisition of M. truncatula by simultaneously increasing N fixation and reducing nitrate uptake from soil. We propose that elevated CO2 causes legumes to rely more on N fixation than on N uptake from soil to satisfy N requirements.
authors: State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, People's Republic of China ; University of Chinese Academy of Sciences, Beijing, People's Republic of China.
authors: Huijuan
authors: H
authors: Guo
authors: Yucheng
authors: Y
authors: Sun
authors: Yuefei
authors: Y
authors: Li
authors: Xianghui
authors: X
authors: Liu
authors: Qin
authors: Q
authors: Ren
authors: Keyan
authors: K
authors: Zhu-Salzman
authors: Feng
authors: F
authors: Ge
mesh_terms: D001272:Atmosphere / Q000737:chemistry; D001692:Biological Transport / Q000187:drug effects; D015415:Biomarkers / Q000378:metabolism; D050260:Carbohydrate Metabolism / Q000187:drug effects; D002245:Carbon Dioxide / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005838:Genotype; D046913:Medicago truncatula / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D009586:Nitrogen Fixation / Q000187:drug effects* / Q000235:genetics; D053204:Root Nodules, Plant / Q000254:growth & development; D012987:Soil / Q000737:chemistry*
chemical_list: D015415:Biomarkers; D009566:Nitrates; D012987:Soil; D002245:Carbon Dioxide; D009584:Nitrogen