Biology Reference
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Figure 7.7
Proposed models for the putative OPX-encoding genes in cyanobacteria.
The phylogenetic tree of the cyanobacterial 16S rRNA sequences was generated by
Maximum-likelihood analysis in MEGA 5.05 (
Tamura et al., 2011
), using the Jurkes-Can-
tor model (
Jukes & Cantor, 1969
) with a gamma-distributed rate of variation across sites.
To assure statistic significance, 1000 bootstraps were used in the computation of each
tree. The number of
opx
homologues present in each organism is indicated in brackets.
The predicted evolutionary events are also depicted. HGT: horizontal gene transfer; LCA:
last common ancestor.
of the
Gloeobacter
sequences is included in clusters I and III (related to the
opxA
and
opxB
ancestor paralogues, respectively) may be related with the
early branching of
Gloeothece
within the radiation of cyanobacteria, which
resulted in the accumulation of numerous mutations in the
opx
genes. This
hypothesis is also coherent with the works reporting that this strain pos-
sesses unique characteristics within the cyanobacterial phylum (
Nakamura
et al., 2003
). Similar to the events predicted for
pcp
, the
Cyanobacterium
also
lost the two ancestor
opx
paralogues during the contraction of its genome.
Interestingly,
Cyanothece
PCC 7822 possesses three OPX. One of the
