INBA   12521
INSTITUTO DE INVESTIGACIONES EN BIOCIENCIAS AGRICOLAS Y AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
ROLE OF SUCROSE IN DIFFERENT CYANOBACTERIA
Autor/es:
KOLMAN, M.A. ; PEREZ CENCI, M.,; NISHI, N.C ; SALERNO, G.L
Reunión:
Workshop; 8th European Workshop on the Molecular Biology of Cyanobacteria. Naantali; 2011
Resumen:
Sucrose (Suc) is one of the most common non-reducing disaccharides in nature, produced by oxygenic photosynthetic organisms. Suc metabolism has been extensively studied in plants and more recently in cyanobacteria. Suc is biosynthesized through a two-step pathway involving sucrose-phosphate synthase (an αD-glucosyltransferase) and sucrose-phosphate phosphatase (a phospho-hydrolase) in both unicellular and  filamentous cyanobacterium strains. Suc  is hydrolysed either by alkaline/neutral invertases (Inv) or sucrose synthase (SuS) (mainly present in filamentous heterocyst-forming cyanobacteria). To investigate the role of Suc in different cyanobacteria we analysed the presence  and localization of its metabolism  enes in genomes sequenced to date, in addition to the functional characterization of key species genes and analyses of null mutants. While in most strains, genes are scattered in the genomes, in a few cases, genes of the biosynthesis pathway are grouped. A particular case is found in the unicellular bloom-forming strain Microcystis  aeruginosa PCC 7806 where the three functionally characterized genes of Suc metabolism are grouped. Moreover, in Synechococcus sp. PCC 7002, the two genes were shown to be cotranscribed.Investigations carried out with null mutants in Suc biosynthesis or hydrolysis encoding genes led us to conclude that Suc is likely not to be essential in unicellular strains, which it does not seem to be the case for filamentous diazotrophic strains. Importantly, in these cyanobacterianitrogen fixation entirely depends on Suc hydrolysis. Suc seems to play an important role in early stages of a salt treatment in unicellular strains (like Synechocystis sp. PCC 6803) but it is dispensable for stress tolerance, which may be ascribed to the presence of other compatible solutes. Importantly, in  filamenous strains, we showed a salt sensitive phenotype related to  the lack of polymers derived from Suc.Taken together our  results suggest  that  in cyanobacteria  the acquisition of Suc metabolism gave some advantage to cyanobacteria to cope with salt/stress conditions, but not as an essential molecule, which, in turn, might have led to its lost in some unicellular marine strains. Later gene reacquisition events, probably by lateral gene transfer either from other cyanobacteria or from proteobacteria that might  have acted as gene reservoirs, might  have given origin to novel roles in some bloom forming and in filament diazotrophic strains. Supported by grants from CONICET (PIP Nº 134), University of Mar del Plata and FIBA