RISE OF THE
MITOCHONDRION
COMMUNITY OF REASON
13 OCTOBER, 2013
MINDY L. WALKER, PH.D.
ASSOCIATE PROFESSOR OF BIOLOGY
ROCKHURST UNIVERSITY
OVERVIEW
• Prok vs. Euk
• Mitochondrial A&P
• Origin of eukaryotic cells, some 2.5 Bya, via
endosymbiosis
• Consequences: separate mitochondrial and chloroplast
genomes
• mtDNA/Mitochondrial Eve
GENERAL PHYLOGENY
PROK’S VS. EUK’S
MITOCHONDRIAL A
MITOCHONDRIAL P
OR, MORE SIMPLY…
EVOLUTION OF EUKARYOTES
• As early as 1.5 Bya, fossil eukaryotic cells appear
Microfossils of probable eukaryotic cells
Reproduced from Schopf, J.W., Scientific American 239 (1978): 111-138. Courtesy of J.
William Schopf, Professor of Paleobiology & Director of IGPP CSEOL
ENDOSYMBIOSIS – CELLULAR INCEPTION
ENDOSYMBIOSIS EXPLAINED
WHAT ABOUT THE OTHER M-B ORGANELLES?
EVIDENCE – EXTANT ENDOSYMBIOTIC SPP.
The ciliate Paramecium bursaria houses hundreds of symbiotic green
algae which can be liberated from the Protistan cell and live
independently
Courtesy of Anthony L. Swinehart, Hillsdale College
EVIDENCE - PROK VS. MITO
EVIDENCE - ORGANELLE DNA DIFFERS FROM NUCLEAR
DNA
1) In location: organelle vs. nucleus
2) In organization: single circular vs. multiple linear strands
3) In function: which proteins are coded for and how are they regulated
4) In mode of replication and inheritance
EVIDENCE - MTDNA
• mtDNA is a single, ds, circular DNA molecule
• There are several copies in each mitochondrion
• mtDNA is similar to prokaryotic DNA: there are no histones, and
mtDNA genes contain no introns
• Because mtDNA is in a highly oxidizing environment, it has a much
higher mutation rate than nuclear DNA
• mtDNA genes code for mitochondrial ribosomes and tRNAs
• mtDNA relies on nuclear gene products for replication and
transcription
EVIDENCE - MTDNA
CHLOROPLAST DNA (CPDNA)
•
CP DNA is a single, ds, circular DNA molecule (the
smallest of the three plant genomes)
•
20-200 copies in every chloroplast
•
Inherited uniparentally from the maternal parent
•
CP DNA contains some 113 genes, 20 of which
contain introns; most of these genes are involved with
photosynthesis and plastid gene expression
•
Structural rearrangements of the genome are rare (but
when they occur, they are useful in establishing
relationships phylogenetically)
ORIGIN OF VARIOUS PHOTOSYNTHETIC
EUKARYOTES
The Origin of early Eukaryotic
Ancestors leading to the
lineages of animals and fungi
was probably an independent
event from that of the origin of
plants
Primary, secondary and tertiary endosymbiosis
Adapted Cracraft, J. and M. J. Donoghue (Eds). Assembling the Tree of Life. Oxford University Press, 2004.
TRANSFER OF GENES BETWEEN ORGANELLES
AND NUCLEUS
• Many genes were transferred to the eukaryotic nucleus and
vice versa
• Chloroplasts synthesize only a small portion of the proteins
they use
• Transfer of nuclear genes coding for symbiotic organelle
proteins
• Such HGTs improve efficiency and reduce the likelihood of
mutations, but complicates their use in establishing
phylogenies
MITOCHONDRIAL DNA IS USED TO STUDY CLOSELY
RELATED SPECIES
– mtDNA’s mutation rate is ten times faster than that of nuclear DNA
– mtDNA is passed down from mother to offspring without recombination
grandparents
mitochondrial
DNA
nuclear DNA
parents
Mitochondrial DNA is
passed down only from
the mother of each generation, so it is
not subject to recombination.
child
Nuclear DNA is inherited from both
parents, making it more difficult to
trace back through generations.
MITOCHONDRIAL EVE
ANCIENT DNA STUDIES
DNA REVEALS THE ABORIGINAL AUSTRALIANS ARE THE
FIRST HUMANS TO LEAVE AFRICA
•
(Science:
•
Aboriginal Australians are the direct descendants
of the first people who arrived on the continent
some 50,000 years ago; those ancestors left Africa
earlier than their European and Asian counterparts
•
Evidence that Aboriginal Australians are
descendants of the earliest modern explorers,
leaving Africa around 24,000 years before their
Asian and European counterparts
•
Contrary to the widely accepted hypothesis that all
modern humans derive from a single out-of-Africa
migration wave into Europe, Asia, and Australia
The study derived from a lock of hair collected by a British anthropologist
one hundred years ago from an Aboriginal man from the Goldfields region of
Western Australia
22 September 2011)
OUT-OF-AFRICA MIGRATION
STUDY OF MITOCHONDRIAL DNA TIES ANCIENT
REMAINS TO LIVING DESCENDANTS
• Compared the complete mitogenomes of 4 ancient and 3 living
individuals from the north coast of British Columbia
• Nothing definitively tied current inhabitants to ancient remains
(5,000 to 6,000 years old) until this direct genetic link
• "Having a DNA link showing direct maternal ancestry dating
back at least 5,000 years is huge as far as helping the
Metlakatla prove that this territory was theirs over the millennia."
– Petzelt
• Problem with using nuclear DNA?
Cui et. al., PLoS ONE 8(7): e66948. doi:10.1371/journal.pone.0066948
THE GENETIC IMPACT OF AZTEC IMPERIALISM: ANCIENT
MITOCHONDRIAL DNA EVIDENCE FROM XALTOCAN, MEXICO
• Indicates that residents of houses before and after the Aztec
conquest have distinct haplotypes that are not closely related
• mt compositions of the temporal groups are statistically different
• Matrilines present in the households were replaced following the
Aztec conquest.
• Indicates that the Aztec expansion may have been associated
with significant demographic and genetic changes within
Xaltocan
Mata-Miguez et al., Am J
Phys Anthropol 000:000–000,
2012.
OTHER APPLICATIONS OF ANCIENT MTDNA
•
Ancient DNA Suggests Dwarf and ‘Giant’ Emu Are Conspecific
•
Ancient DNA Analysis Affirms the Canid from Altai as a Primitive Dog
•
Highly Informative Ancient DNA ‘Snippets’ for New Zealand Moa
•
Investigating the Global Dispersal of Chickens in Prehistory Using Ancient Mitochondrial DNA Signatures
•
Ancient DNA Assessment of Tiger Salamander Population in Yellowstone National Park
•
Mitochondrial Phylogenomics of Modern and Ancient Equids
•
Mitochondrial DNA Variation, but Not Nuclear DNA, Sharply Divides Morphologically Identical Chameleons along an
Ancient Geographic Barrier
•
Origins and Evolution of the Etruscans’ mtDNA
•
Multiplexed SNP Typing of Ancient DNA Clarifies the Origin of Andaman mtDNA Haplogroups amongst South Asian
Tribal Populations
•
Ancient mtDNA Analysis of Early 16 th Century Caribbean Cattle Provides Insight into Founding Populations of New
World Creole Cattle Breeds
•
The Phylogeny of the Four Pan-American MtDNA Haplogroups: Implications for Evolutionary and Disease Studies
•
mtDNA from the Early Bronze Age to the Roman Period Suggests a Genetic Link between the Indian Subcontinent
and Mesopotamian Cradle of Civilization
•
A Reevaluation of the Native American MtDNA Genome Diversity and Its Bearing on the Models of Early
Colonization of Beringia
•
A Mitogenomic Phylogeny of Living Primates
•
Mitochondrial DNA Evidence for a Diversified Origin of Workers Building Mausoleum for First Emperor of China
QUESTIONS?
**CHIEFS CHECK**