INBA   12521
INSTITUTO DE INVESTIGACIONES EN BIOCIENCIAS AGRICOLAS Y AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Regulation of photosystem expression by oxygen and light in Bradyrhizobium sp. C7T1 strain
Autor/es:
MONTECCHIA, MARCELA S.; PUCHEU, NORMA L.; KERBER, NORMA L.; GARCÍA, AUGUSTO F.
Lugar:
Los Cocos, Córdoba, Argentina
Reunión:
Congreso; XXIII Reunión Latinoamericana de Rhizobiología; 2007
Institución organizadora:
RELAR
Resumen:
Photosynthetic bradyrhizobia nodulate stems and/or roots of some Aeschynomene species. The effect of oxygen and light on the expression of the photosynthetic apparatus in an indigenous Bradyrhizobium sp. C7T1 strain was assessed. The expression of the puf operon, which encodes most of the apoproteins of light-harvesting and reaction center complexes, was estimated by the accumulation of its mRNA and bacteriochlorophyll (BChl) in cells and membrane. This strain produces photosynthetic pigments when grown under cyclic illumination or darkness. Oxygen, although absolutely required for growth, showed some inhibitory effect on the photosystem formation. A decrease in oxygen tension from 21% to 0.5% is shown to enhance puf expression and the BChl-content in cells grown under a light/dark regime. Interestingly, continuous white light illumination at 21% oxygen tension completely abolished BChl synthesis while it significantly increased the puf operon expression level compared to cells grown under a light/dark cycle, suggesting a light dependent posttranslational regulation of BChl synthesis and photosystem formation. Based on the BChl content detected in Bradyrhizobium sp. C7T1 under various light regimes we showed that the formation of the photosynthetic apparatus is not induced by far red light as shown for other strains of photosynthetic bradyrhizobia.