INBA   12521
INSTITUTO DE INVESTIGACIONES EN BIOCIENCIAS AGRICOLAS Y AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Relationship between carbon and nitrogen metabolism in the marine photosynthetic picoeukaryote Ostreococcus tauri.
Autor/es:
G.F. CALÓ; H.G. PONTIS; G.L. SALERNO
Lugar:
San Miguel de Tucumán
Reunión:
Congreso; VII Congreso Argentino de Microbiología General; 2011
Institución organizadora:
Universidad Nacional de Tucumán
Resumen:
Picoeukaryotes are a taxonomically diverse group of microorganisms
with less than 2 micrometers in diameter. In this group photosynthetic
picoeukaryotes (PPEs) are widely distributed from temperate to polar marine habitats, being
significant contributors to primary production. PPEs, Prasinophytes are marine
planktonic green algae with a phylogenetic position branching near the base of
the green lineage that evolved after the endosymbiosis event that gave rise to
photosynthetic eukaryotes. Marine PPEs of the genus Ostreococcus thrive in ecosystems ranging from oligotrophic to
eutrophic environments and could be key organisms for biogeochemical fluxes of
modern oceans during climate change. In the green lineage the most important
soluble disaccharide is Sucrose (Suc), which mainly occurs in oxygenic
photosynthetic organisms, including land plants, unicellular algae and
cyanobacteria. Trehalose (Tre) is another important non-reductant disaccharide
distributed in nature, is accumulated mainly in bacteria, fungi, and arthropods,
but not in land plants. In addition to its role as energy and carbon source,
accumulation of Tre has been associated with improved stress tolerance towards
both biotic and abiotic stress situations. Its role in the green lineage is still controversial. The aim of this study
was to investigate which are the important soluble carbohydrates in O. tauri and its relationship with
nitrogen assimilation. Preliminary experiments showed that Tre but not Suc is
the main soluble sugar in this Prasinophyte. Tre content increases in O. tauri cells grown under nitrogen
deficiency in a time-dependent manner. Total reducing sugars and starch levels
were measured in parallel. An
opposite pattern was observed with total sugars reducing content. On the other hand, starch content also showed a high increase under
nitrogen deficiency. Reversion of that condition restored carbohydrates to
basal levels. The enzyme activity responsible
of Tre synthesis (TPS, Tre-Phosphate Synthase) and expression at the mRNA level
paralleled the accumulation of the disaccharide. We conclude that Tre plays an important
physiological role as principal soluble sugar interconnecting carbon and nitrogen
metabolism in O. tauri.