Download Selection for mitochondrial quality drives the evolution of

ARUNAS RADZVILAVICIUS
SELECTION FOR MITOCHONDRIAL QUALITY
DRIVES THE EVOLUTION OF GERMLINE AND TWO SEXES
SOMATIC GAMETOGENESIS OR
GERMLINE SEQUESTRATION?
WHY IS OOGAMY UNIVERSAL IN
MULTICELLULAR ORGANISMS?
MATING TYPE
A
MATING TYPE
B
MODELLING THE INVOLVEMENT
OF MITOCHONDRIA
Random partitioning
of mitochondria
generates variation
ZYGOTE
+
x2
Isogamy: mitochondria inherited from only one (UPI)
or both (BPI) mating types. Ancestral metazoan state.
BPI if mutation rate was low.
MALE
FEMALE
Two types of
mitochondrial mutations:
ZYGOTE
+
ROS, UV
Oogamy: universal in multicellular plants and animals,
seldom seen in unicellulars.
mtDNA replication errors
Background damage
Zygote
fitness
Totipotent
stem cells
Stem cell
fitness
Tissue
stem cells
Fixation probability of oogamy
(evolutionary advantage)
OOGAMY EVOLVES TO ENSURE UPI AND MAINTAIN SOMATIC FITNESS
Somatic
fitness
Adult fitness depends on the worst tissue, so high
mitochondrial fitness variation between tissues is selected
against.
ISOGAMY:
BPI, low variation between organisms
Small zygote, high variation in soma
+
Egg size (log, units of sperm size)
OOGAMY:
UPI, high variation between organisms
Large zygote, low variation in soma
+
INCREASING MITOCHONDRIAL MUTATION RATE DRIVES THE EVOLUTION OF GERMLINE
Replication mutation rate (x10-3)
A trade-off between the generated
beneficial variation and the amount of
accumulated deleterious mutations
5
More tissues
Large egg
Metazoan motility, predation
Faster accumulation of mtDNA
mutations
M50 0T BPI Q0
4
Early germline sequestration
3
Unlimited somatic differentiation,
greater activity, ageing
2
Cambrian explosion
1
0
2
4
6
8
Increasing somatic complexity makes somatic
gametogenesis even more stable. Only high mtDNA
replication rates make early germline sequestration
evolutionary advantageous.
10
Background mutation rate (x10-3)
Somatic gametogenesis
advantageous (10 divs)
0
More
mitochondria
Neoproterozoic oxygenation
0.05
Germline
advantageous (3 divs)
0.1
0.2
0.3
Fixation probability of g
CoMPLEX AND
DEPARTMENT OF GENETICS,
EVOLUTION AND ENVIRONMENT
UNIVERSITY COLLEGE LONDON
[email protected]
Twitter @LukeArn
THANKS TO:
CoMPLEX
NICK LANE
ANDREW POMIANKOWSKI