Papel de mtmtp2 y mtatx1 en el tráfico intracelular de metales en nódulos de medicago truncatula

Abstract

Abstract Symbiotic nitrogen fixation is a primary source of assimilable nitrogen in natural ecosystems. The interaction established between legumes and diazotrophic bacteria known as rhizobia is one of the best understood. In this relationship, new organs are developed, the root nodules, where symbiotic nitrogen fixation takes place. The process requires relatively large amounts of transition metal as cofactors of many of the enzymes participating in it. In this PhD Thesis, we characterized two genes in the M. truncatula and S. meliloti symbiosis related with zinc and copper homeostasis (MtMTP2 and MtATX1, respectively). MtMTP2 is nodule-induced Zn-effiux protein that was localized in the endoplasmic reticulum in root epidermal and endodermal cells, as well as in nodule cells. Loss of MtMTP2 function resulted in altered nodule development and bacteroid differenciation, changes in zinc homeostasis and a severe reduction of nitrogenase activity. MtATX1 is a nodule-specific Cu+-chaperone that is expressed in nodule cells. Its abscense reduces plant growth and nitrogenase activity. Both genes are required for effective symbiotic nitrogen fixation in M truncatula.