INVESTIGADORES
VARGAS Walter Alberto
congresos y reuniones científicas
Título:
Sucrose degradation in salt-treated cyanobacteria
Autor/es:
NICHI, CN; KOLMAN, MA; VARGAS, WA; SALERNO, GL
Lugar:
Porto
Reunión:
Simposio; 14th International Symposium on Photosynthetic Prokaryotes; 2012
Resumen:
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All organisms have to cope
to the constantly changing environment in order to survive, and cyanobacteria
are by no means the exception to that. In particular, cyanobacteria can grow
under a wide range of environmental conditions, including salinity. Stenohaline
cyanobacteria (with low salt tolerance) accumulate various low molecular osmolytes
mainly sucrose (Suc), trehalose and sucroglucans. Suc is one of the most abundant
disaccharide in nature and was reported to be present in oxygenic
photosynthetic organisms. In particular, Suc metabolism has been biochemically,
functionally and physiologically characterized in unicellular and
heterocyst-forming cyanobacterial strains. In Anabaena sp. PCC 7120, Suc can be hydrolysed by two
alkaline-neutral invertase isoforms (Inv-A and Inv-B) [1,2] or cleaved by
sucrose synthase (SuS) [3]. In contrast, in the unicellular strain Microcystis aeruginosa PCC 7806 only SuS
is responsible of Suc catabolism [4]. The aim of this study was to investigate
the effect of a salt treatment on the expression of Suc degradative proteins
and the role of Inv-A and Inv-B in Anabanea
cells submitted to a salt stress. The expression of SuS or Inv encoding genes
increased after salt addition. Also, Inv-A or Inv-B were not essential to cope
the stress, when the growth of insertional mutants (lacking Inv-A or Inv-B) was
determined. However, the accumulation of sucroglucans and glycogen was affected
by the presence of NaCl. In the case of M.
aeruginosa, both Suc accumulation and Suc cleavage by SuS increased with
the salt treatment, indicating a sugar cycling during the stress. Taken
together, our results suggest that Suc in not a mere salt-response osmolyte, and
that a Suc cycling mechanism may be operating in both filamentous
heterocyst-forming and unicellular bloom-forming strains in response to salnity
