Sucrose synthase in cyanobacteria and its relationship with hypoxic stress

KOLMAN, M.A.; SALERNO, G.L.

Austin, Texas

Congreso; Plant Biology 2012; 2012

American Association of Plant Biologists

Higher plants and cyanobacteria metabolize sucrose (Suc) by a similar set of enzymes. Suc utilization requires the breakdown of the glycosidic bond, which depends on the action of Suc synthase (SuS, U/ADP-glucose: D-fructose 2-a-D-glucosyl transferase, EC 2.4.1.13), a readily reversible glucosyltransferase that yields a sugar nucleotide and fructose, or of invertases. In plants SuS plays a critical function in long-distance carbon allocation, stress responses, symbiotic interactions and in Suc to polysaccharides interconversion. Whereas in plants SuS is ubiquitous, its occurrence in cyanobacteria has been only reported in filamentous heterocyst-forming strains and in some unicellular strains with unusual characteristics. Following recent reports in plants on the importance of SuS during and after exposure to hypoxia/anoxia conditions, we analyzed the effect of hypoxia on SuS gene expression in different cyanobacteria. Transcript levels increased after hypoxic treatment either in unicellular (M. aeruginosa PCC 7806 and G. violaceus PCC 7421) or heterocyst-forming (Anabaena sp. PCC 7119) strains, being a reversible effect. Also we followed the growth of the wild-type (PCC 7119 strain) and of two derivative mutants (susA- and susA+, lacking or over-expressing SuS, respectively) after hypoxia, and after oxygen supply restoration. We conclude that SuS is important in the recovery of growth after the stress. Similarly to plants, these results indicate that SuS is involved in Suc utilization in metabolically highly active cells where ATP synthesis may be limited by low oxygen tension. Supported by CONICET (PIP 134 and CEBB-INBA), UNMdP (EXA552/11), and FIBA.