Chlamydomonas
623
−
NH
4
+
−
NH
4
+
Gamete
Gamete
Fusion
Zygote
Vegetative zygote
Meiosis
Mitosis
Vegetative
cycle of mt
−
Vegetative
cycle of mt
+
−
−
−+
+
n
−
n
n
n
+
+
−+
−+
Fig. 2
Life cycle of
C. reinhardtii
: mt, mating-type; n, nucleus; the chloroplast is shown below
the nucleus. See text for explanation. [Reproduced with permission from J.-D. Rochaix, FEMS
Microbiol. Rev
.
46
: 13–34 (1987).]
parent becomes associated with the nu-
cleus from the other.
2
Three Autonomous Genetic Systems
Like higher plants,
Chlamydomonas
con-
tains three genetic systems, located in
the nucleocytosol, the chloroplast, and the
mitochondria. In contrast to nuclear genes,
which are transmitted to the offspring in
a Mendelian fashion, chloroplast and mi-
tochondrial DNAs are usually transmitted
uniparentally from the mating-type
+
and
mating-type
−
parent respectively. In
C.
eugametos
and
C. moewusii
,bo
thorgane
l
-
lar genomes are transmitted uniparentally
from the mating-type
+
parent (Table 1).
Tab. 1
Three genetic systems in
Chlamydomonas
.
System
Species
Complexity
of genome
[kb]
Number of
linkage groups
Copy
number
Inheritance
Nucleus
reinhardtii
10
5
17
Me
Chloroplast
reinhardtii
204
1
80
up
+
eugametos
343
1
up
+
moewusii
292
1
up
+
Mitochondria
reinhardtii
15.8
1
50
up
−
eugametos
20.2
1
up
+
moewusii
18.5
1
up
+
Notes
: Me: Mendelian inheritance; up
+
,up
−
: uniparentally inherited from the mating-type
+
and
mating-type
−
parent respectively.
