INBIOTEC   24408
INSTITUTO DE INVESTIGACIONES EN BIODIVERSIDAD Y BIOTECNOLOGIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Occurrence of sucrose metabolism in bloom-forming cyanobacteria
Autor/es:
M.A. KOLMAN; G.L. SALERNO
Lugar:
Texel
Reunión:
Workshop; 9th European Workshop on Molecular Biology of Cyanobacteria; 2014
Institución organizadora:
NIOZ and Federation of European Microbiological Societies
Resumen:
Studies in cyanobacteria and
the availability of complete genome sequences have significantly increased our
knowledge of the structure of proteins involved in sucrose (Suc) metabolism, their
origin and further evolution. Studies in nitrogen-fixing filamentous strains
and in Synechocystis sp. PCC 6803 led
us to conclude that Suc-phosphate synthase (SPS) and Suc-phosphate phosphatase
(SPP) [enzymes involved in Suc biosynthesis], and Suc synthase (SuS) [enzyme
involved in Suc degradation] are proteins with modular architectures that might
have arisen from functional domains shuffled during evolution. In cyanobacteria,
Suc was identified as the main compatible osmolyte in many fresh-water strains,
and as a minor or transient part of the total compatible solute pool in more
halotolerant strains that accumulate also other organic compounds. However, Suc
net accumulation, which can be ascribed to an increase of the expression of Suc
biosynthesis enzymes, is also accompanied by an enhancement in Suc degradation
by SuS, either in filamentous or unicellular strains. Recently, we have also
characterized SuS from unicellular strains, like Microcystis aeruginosa PCC 7806. In the present work we studied the
presence of Suc metabolism in bloom-forming cyanobacteria. In silico analyses revealed that putative SPS, SPP and SuS encoding
genes (sps-like, spp-like and sus-like)
are only present in a few bloom-forming strains. Among Nostocales and
Stigonematales the distribution of genes related to Suc metabolism is
ubiquitous, except for the strain Raphidiopsis
brokii D9. Remarkably, among Chroococcales and Oscillatoriales sps- and spp-like sequences were only found in M. aeruginosa PCC 7806, being absent in other M. aeruginosa genomes, and in Leptolyngbya
boryana PCC 6306, respectively. We functionally characterized SPS and SPP
encoding genes from M. aeruginosa PCC
7806 and demonstrated that their expression is increased in response to a salt
treatment. Moreover, the sus gene is
located between the sps and spp with an intergenic distance of 160
and 6 bp, respectively, defining a transcriptional unit named Suc cluster (suc). Among all Suc-containing
cyanobacteria whose genomes are fully sequenced to date, the gene organization
of the Suc cluster present in M.
aeruginosa PCC 7806 is unique.
A global comparison of the genome in M. aeruginosa PCC 7806 (suc+) and the rest of the M. aeruginosa genomes (suc−) do not show the presence of
syntenic regions. Our results and the cluster organization analysis of Suc
metabolism genes led us to suggest that in the bloom-forming strains Suc genes
might have been lost and later acquired by horizontal gene transfer from
filamentous strains.