Acquisition of nitrogen through mycorrhizaeThe evolution ofsymbiotic gene networksin plants[8,9] andloss of pathogenicity determinants in fungi, especially ofthose belonging to Glomeromycota order [10] enabled thedevelopment of mycorrhiza, the intraradical symbiosis providing partners with increased fitness and ecological advantage.Ecto-mycorrhiza and endo-mycorrhiza allowed plants toincrease the surface of explored soil via an extended hyphalnetwork transporting water, phosphorous and nitrogen nutrients. Studies using isotope labelling and differential gene expression showed that arbuscular mycorrhiza (AM) fungitake up ammonia from the soil and use glutamine synthetasein the extraradical mycelia (ERM) to convert the inorganicnitrogen into aminoacids via glutamine synthetase (GS) andglutamate synthase (glutamine:2-oxoglutarate aminotransferase; GOGAT) pathway