Benzylaminopurine (BAP) modifies the source-sink relation in wheat by inhibition of sugar and amino acids export to phloem

M. VICTORIA CRIADO; CARLA CAPUTO; IRMA N.ROBERTS; SUSANA PASSERON; ATILIO J. BARNEIX

Pinamar, Buenos Aires, Argentina

Congreso; X Congress PABMB, XLI Reunión anual de la SAIB; 2005

Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular

Nitrogen (N) deficiency stimulates protein degradation and N remobilization from old to young leaves. When N deficiency was imposed to wheat plants (N-plants), there was a fast decrease in protein and amino acids and an increase in sugar concentrations in the third fully expanded leaf. In the phloem exudates there was a decrease in amino acids but not in sugar concentrations. After four days of N starvation, the expanding leaves showed a lower protein and chlorophyll content than in the N+ plants. Glutamine synthetase (GS1), but not GS2 and glutamate dehydrogenase (GDH) activities increased in the N-plants. However, when plants were supplied with 20 µM BAP, soluble proteins and sugars content increased in the third leaf, while soluble sugars and amino acids concentration decreased in the phloem exudates in both conditions. In expanding leaves a decrease in proteins and chlorophyll, but not in amino acids and sugars could be observed with or without N supply. BAP addition also increased GS1 but not GS2 and GDH activity. These results suggest that BAP affects the source/sink relationship in the plant by decreasing the amino acids and sugars phloem loading, and that GS1 is involved in amino acids cycling within the cell.