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One of the biggest challenges of 21st century is the food production to be adequate enough to cover the needs of the continually increased human population. The Green Evolution was established mainly by the use of nitrogen fertilizers, fertilizers that seriously affect the environment and human health, and in addition have a high financial cost. Molecular nitrogen (N2) is extremely abundant, comprising about 79% of the atmosphere. However, plants cannot convert N2 to useful organic forms and mineral nitrogen is limited in soils, commonly restricting the plant growth.

To reduce the production cost and to guarantee that the soil, the water, the energy, and the biological natural resources are protected, there is a demand for introduction and application of Sustainable Agriculture strategies. Legumes are the sustainable agriculture’s lynch pin because they are unique among crop plants in the ability to fix N2 in symbiotic association with bacteria called rhizobia. Cultivated legumes fix 40-60 million tons of nitrogen annually, concomitantly accounting for approximately one third of the world's crop production. Food-legumes include bean, soybean, pea, and lentil, whereas alfalfa and clover are forage plants.

Symbiotic nitrogen fixation (SNF) takes place in legume root nodules, tumor-like structures where N2 fixation is catalysed by the bacterial nitrogenase, an enzyme that requires a highly regulated hypoxic microenvironment and is very sensitive to alterations in plant C and N metabolism. The produced ammonia is incorporated by the plant into important biomolecules and in return, the plant furnishes bacteroids with organic acids.

The aim of this work will be to study the nodule-specific hypoxia-related regulation of genes involved in carbon allocation and metabolism, within the symbiotic system of Medicago truncatula – Sinorhizobium meliloti, and to analyse its putative implication in the SNF. In particular, we are going to search for evidence of such a regulation in nodule-specific expressed and nodule-induced genes related to nutrient transport and metabolism, emphasizing on the corresponding sugar transporters and glycolysis enzymes isoforms. The results of this study will greatly improve our knowledge on the transcriptional regulation that governs nodule development and establishment of the symbiotic nitrogen fixation.