Chlamydomonas
625
an internal symbiotic relationship with
the ancestor of eukaryotic plants and
green algae. Other similarities between
chloroplasts and photosynthetic bacteria
supporting this theory are discussed in the
paragraphs that follow.
Sequencing of the chloroplast genome of
C. reinhardtii
has revealed that it contains
99 genes. They include genes involved in
photosynthesis, genes of the components
of the chloroplast gene expression system,
genes involved in posttranslational steps,
and other genes of unknown function
(F
ig
.3
,Tab
le2
)
.Manyo
fthesegenesare
also found in the plastid genomes of higher
and lower plants. Although the chloroplast
genome of
C. reinhardtii
is larger than
those of land plants, it has lost numer-
ous coding regions that are still present
in other chloroplast genomes. The large
size of the chloroplast genome of
C. rein-
hardtii
is due to the presence of many
2791
psbC
petL
psaC
F
M
H
N
rpoC1-2
rpoC1-1
271
140
V
R
P
E
Wendy
polA
petD
chlB
psbK
tudA
C
T
R2
S
W
rpl20
clpP
petB
L
IR
A
IR
B
5
4
3
2
1
psbA
psbD
psaA exon 2
psbJ
atpl
psaJ
rps12
1995
atpB
16S
l
A
7S
3S
23S-1
23S-2
5S
tscA
rbcL
G
S
atpE
ycf12
rps7
rps14
psbM
psbZ
ccsA
psaA exon 3
psbH
psbT
psbB
L
E
D
rpoA
rps2-2
rps2-1
rps18
ycf3
ycf4
rps9
rboB-2
rboB-1
psbE
M
chlL
rpl36
rpl23
rpl2
rps19
rpl16
rpl14
rpl15
rps8
psaA exon 1
G
M
rps4
16S
l
A
7S
3S
23S-1
23S-2
5S
psbN
5
4
3
2
1
psbA
ch/N
K
atpF
atpH
cemA (
g
ct10)
psbl
atpA
psaB
rpo C2
rps3
petG
psbL
psbF
Q
Y
Fig. 3
Map of the chloroplast genome of
C.
reinhardtii
with transcribed regions. See Table 2
for gene nomenclature. The outer circle indicates
the transcribed regions: monocistronic RNAs
(black), polycistronic RNAs (gray). [Reproduced
with permission from Lilly et al.
Plant Cell
14
,
2681–2708 (2002).]
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