Biology Reference
In-Depth Information
of genome segments and LGT events as the probable causes but attributed the large genome size
due to whole genome duplication (Sugaya
et al
., 2004).
xv) Genome of Nostoc azollae 0708
:
Ran
et al
. (2010) published the complete genome sequence of the
endosymbiont of
Azolla fi liculoides
and reported complete genome erosion in
N
.
azollae
0708. It has
a circular chromosome of 5,846,145 bp with a low G+C content (38.3%) with two circular plasmids
(Fig. 7). Of the 5,337 ORFs, the number of functional coding sequences is 3,668 while the rest of
them are represented by pseudogenes. The proportion of pseudogenes to the number of predicted
genes has been found to be highest in one of the plasmids P1 (63:51) followed by the chromosome
(1623:3206) whereas in the second plasmid P2 it was 3:11. The accumulation of pseudogenes in
certain important processes of DNA replication (
dnaA
) on the main chromosome and on the plasmid,
Chromosome
Coding sequences
Pseudogenes
Remains of insertion elements
Figure 7:
Map of the main chromosome, and plasmids (P1, P2) of the '
Nostoc azollae
' 0708 genome. The distribution of
pseudogenes (red) and remains of insertion elements (blue) are indicated. Predicted genes are indicated by grey color. The
highest level of gene erosion (number of pseudogenes:number of predicted genes) is found in the plasmid P1. Note that the
occurrence of insertion elements appears to be correlated with the distribution of pseudogenes. The P1 and P2 plasmids only
contain two and one remains of insertion elements, respectively. With the kind permission of B. Bergman, Department of
Botany, Stockholm University, Stockholm, Sweden. [Ran
et al
. (2010)
PLoS ONE
5(7):
e11486. doi:10.1371/journal.pone.0011486]
doi:10.1371/journal.pone.0011486.g003.
Color image of this figure appears in the color plate section at the end of the topic.
