Biology Reference
In-Depth Information
Figure 9:
Schematic representation of the synteny within the vicinity of the
nif
gene clusters. The scheme represents the 15 kb
gene cluster containing the
nifHDK
and the other 13 nitrogen fi xation related genes in
Cylindrospermopsis raciborskii
CS-505
compared with the
nif
1 and
nif
2 gene clusters of
Anabaena variabilis
ATCC 29413 and the synteny regions between
C
.
raciborskii
CS-505 and
Raphidiopsis brookii
D9. The synteny regions between
C
.
raciborskii
CS-505 and
R
.
brookii
D9 are delimited by the
arrows.
nif
genes are represented by light grey and dashed lines. Genes in black correspond to hypothetical proteins and grey
genes to proteins with assigned function. With the kind permission of Mónica Vásquez, Department of Molecular Genetic
and Microbiology, Faculty of Biological Sciences, Pontifi cia Universidad Católica de Chile, Santiago, Chile & Millenium
Nucleus EMBA, Santiago, Chile. [Stucken
et al
. (2010)
PLoS ONE
5(2):
e9235. doi:10.1371/journal.pone.0009235] doi:10.1371/
journal.pone.0009235.g003.
freshly isolated symbionts of the former host from Senegal the 11 kb element was absent while the
symbionts of the latter (freshly isolated as well as the cultured strains) showed the presence of
xisA
gene (Meeks
et al
., 1988). There is considerable variation in the length of
nifD
element in the different
cyanobacteria examined so far. The shortest
nifD
element is found in
Anabaena
sp. strain ATCC 33047
(4 kb; Henson
et al
., 2005) and the largest (24 kb) in
N. punctiforme
ATCC 29133 (Meeks
et al
., 2001)
with the intermediate size of 11 kb detected in
Anabaena
sp. strain PCC 7120 (Golden
et al
., 1985; 1988)
and
A
.
variabilis
ATCC 29413 (Brusca
et al
., 1989). In all the
nifD
elements of these cyanobacteria the
xisA
gene is located closest to the 3'-end of
nifD
.
Anabaena
sp. strain ATCC 33047 is an exception
in possessing a changed 11-bp repeat nearest to the
xisA
by one nucleotide (CGGAGTAATTC)
while the direct repeat farthest from
xisA
is identical (CGGAGTAATCC) to the direct repeats from
all others (Henson
et al
., 2005). There appears to be considerable sequence conservation in all the
