Journal
PLANTA
Volume 235, Issue 5, Pages 955-964Publisher
SPRINGER
DOI: 10.1007/s00425-011-1542-5
Keywords
Gloeobacter violaceus; Hypoxia; Microcystis aeruginosa; Salt stress; Sucrose metabolism; Thermosynechococcus elongatus
Categories
Funding
- CONICET [PIP 134]
- Universidad Nacional de Mar del Plata
- FIBA
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Higher plants and cyanobacteria metabolize sucrose (Suc) by a similar set of enzymes. Suc synthase (SuS, A/UDP-glucose: d-fructose 2-alpha-d-glucosyl transferase) catalyzes a reversible reaction. However, it is in the cleavage of Suc that this enzyme plays an important role in vivo, providing sugar nucleotides for polysaccharide biosynthesis. In cyanobacteria, SuS occurrence has been reported in heterocyst-forming strains, where it was shown to be involved also in nitrogen fixation. We investigated the presence of sequences homologous to SuS-encoding genes (sus) in recently sequenced cyanobacterial genomes. In this work, we show for the first time the presence of SuS in unicellular cyanobacterium strains (Microcystis aeruginosa PCC 7806, Gloebacter violaceus PCC 7421, and Thermosynechococcus elongatus BP-1). After functional characterization of SuS encoding genes, we demonstrated an increase in their transcript levels after a salt treatment or hypoxic stress in M. aeruginosa and G. violaceus cells. Based on phylogenetic analysis and on the presence of sus homologs in the most recently radiated cyanobacterium strains, we propose that sus genes in unicellular cyanobacteria may have been acquired through horizontal gene transfer. Taken together, our data indicate that SuS acquisition by cyanobacteria might be related to open up new ecological niches.
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