REGULATION OF GLUTAMINE SYNTHETASE ISOFORMS BY NITROGEN AND CYTOKININS

CARLA CAPUTO; M. ALEJANDRA GELSO; M. VICTORIA CRIADO; IRMA N.ROBERTS; ATILIO J. BARNEIX

Mar del Plata

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.; 2007

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.

Glutamine synthetase plays a central role in the assimilation and re-assimilation of ammonia. We studied the regulation of platidic (GS2) and cytosolic (GS1) isoforms in leaves of wheat plants supplies with the synthetic cytokinin 6- benzylaminopurine  (BAP). Plants were cultivated for 15 d in controlled conditions with 10 mM N in the nutrient solution before the beginning of 48 h of N deficiency and/or BAP. The expression analysis was carried out by semi-quantitative RT-PCR, proteins were visualised by western blot using a pine antibody anti-recombinant GS1 and the activity was determined by the transferase method after the separation of the isoforms in an anion exchange chromatography (Q-sepharose). When N deficiency was imposed to plants (N-), GS2 mRNA, polipeptide and activity decreased. These effect could be reverted with the addition of 20 µM BAP. However BAP supply to N+ plants did not produce any significant change. However, N starvation and BAP addition both induced an increment in GS1 mRNA, polipeptide and activity, which was higher in BAP plants, but no additive effect between treatments was observed. The data support the concept that GS1 and GS2 play a central but different role in N allocation and highlight the need for further studies of its physiological role in wheat. Supported by grants from CONICET and ANPCyT