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Characterization of the Plasma Membrane proton pump ATPases (PM-H+-ATPasas) in potato plants (Solanum tuberosum L.)STRITZLER Margarita, MUÑIZ GARCÍA María Noelia, MURO María Catalina, CAPIATI Daniela AndreaInstituto de Investigaciones en Ingeniería Genética y Biología Molecular ?Dr. Héctor N. Torres? (INGEBI-CONICET). Ciudad de Buenos Aires, Argentina. e-mail: mstritzler@dna.uba.arThe Plasma Membrane proton pump ATPases (PM-H+-ATPases) of plant cells act as primary transporters. Coupled with ATP hydrolysis, they pump protons from the cytoplasm to the apoplast, thus establishing the proton electrochemical gradient that contributes to the maintenance of pH and drives the secondary transport of ions and metabolites. PM-H+-ATPases are involved in many physiological processes in higher plants, as phloem loading, nutrient uptake by the roots, stomatal opening and closure, osmotolerance and stress response. PM-H+-ATPases in higher plants are encoded by a multigene family. We identified seven sequences for putative PM-H+ATPases in the S. tuberosum Phureja genome (PHA1-7) and corroborated de expression of six of them in different tissues of S. tuberosum cv. Spunta. The aim of this work was to determine the role of PM-H+-ATPasas in the tuberization process and stress responses. The expression of PM-H+ATPases during tuberization and in response to hormones that regulate this process (gibberelic acid, abscisic acid and auxins) was determined. The involvement of the PM-H+ATPases in tuber formation was analyzed using specific inhibitors and activators in potato plants. Expression of PM-H+ATPases under different abiotic stress conditions was determined. A transgenic potato plant over-expressing PHA1 was generated to determine the physiological role of this particular isoform.