title: Nitrate application or P deficiency induce a decline in Medicago truncatula N2-fixation by similar changes in the nodule transcriptome.
abstract: Nitrogen fixation of Medicago truncatula is regulated by the nitrogen status of leaves through inducing a repeatedly occurring 24-h nodule activity rhythm that reduces per day nitrogen fixation. The hypotheses of the present study were that (1) long-term moderate whole-plant P deficiency in Medicago truncatula induces an according daily rhythm in nitrogenase activity comparable to that induced by nitrate application and (2), the changes in the nodule transcriptome that go along with a strong nitrogenase activity decline during the afternoon would be similar under P deficiency or after nitrate supply. The nodules of plants in a low P treatment developed a rhythmic pattern of activity that resembled the pattern following nitrate application. A comprehensive, RNAseq-based comparative transcriptome profiling of nodules during a repeated part of the rhythm revealed similarities between P deficiency versus nitrate supply. Under both treatments, the formation of nitrogenase was targeted by a reduction in the expression of genes for nodule-specific cysteine-rich peptides (NCR), and possibly also by a disturbance of the inner cell iron allocation. A strong reduction in the expression of leghemoglobin is likely to have restricted the supply of oxygen for respiration.
authors.affiliation: Department of Crop Science, Section for Plant Nutrition and Crop Physiology, Faculty of Agriculture, University of Goettingen, Carl-Sprengel-Weg 1, 37075 Goettingen, Germany.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Liese
authors.affiliation: Department of Crop Science, Section for Plant Nutrition and Crop Physiology, Faculty of Agriculture, University of Goettingen, Carl-Sprengel-Weg 1, 37075 Goettingen, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Schulze
authors.affiliation: Departmento de Producción Agrícola, Facultad de Ciencias Agrarias, Universidad de Talca, Casilla 747, Talca, Chile.
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Cabeza
mesh_terms: D018533:Biomass; D018506:Gene Expression Regulation, Plant; D046913:Medicago truncatula / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D009586:Nitrogen Fixation; D010758:Phosphorus / Q000172:deficiency* / Q000378:metabolism; D053204:Root Nodules, Plant / Q000235:genetics* / Q000378:metabolism*
chemical_list: D009566:Nitrates; D010758:Phosphorus