Mitochondrial DNA in Molecular Systematics Mitochondria organelle found

  • Slides: 16
Download presentation
Mitochondrial DNA in Molecular Systematics

Mitochondrial DNA in Molecular Systematics

Mitochondria - organelle found in eukaryotic cells - cellular respiration – ATP production

Mitochondria - organelle found in eukaryotic cells - cellular respiration – ATP production

Mitochondria Evolution • Endosymbiotic Theory – Ivan Wallin (1920 s) and Lynn Margulis (1981).

Mitochondria Evolution • Endosymbiotic Theory – Ivan Wallin (1920 s) and Lynn Margulis (1981). • Proto-Eukaryotic cell incorporated a protobacterial cell and formed a symbiotic relationship (a billion years ago). cyanobacteria Primordial eukaryotic cell Eukaryotic cell Perform Symbiotic Relationship

mt. DNA • mt. DNA is maternally inherited in animals and plants. • More

mt. DNA • mt. DNA is maternally inherited in animals and plants. • More than 1300 complete mitochondrial sequences have been generated. • Most of the mitochondrial complete sequences are belonged to animals and algae. • Only a few plant species have their mitochondrial genome sequenced: Nicotiana tabacum, Oryza sativa, Triticum aestivum, Zea mays, Sorghum bicolor, Marchantia polymorpha. • Plant mt. DNA is far more complex than animal mt. DNA – larger size (300 -600 kb) and variable in size (up to 2000 kb).

Comparison of Plant mt. DNA and cp. DNA Plant species Nicotiana tabacum Oryza sativa

Comparison of Plant mt. DNA and cp. DNA Plant species Nicotiana tabacum Oryza sativa Triticum aestivum Zea mays Sorghum bicolor Marchantia polymorpha cp. DNA mt. DNA 156 kb 135 kb 140 kb 141 kb 121 kb 431 kb 492 kb 453 kb -680 kb 496 kb 187 kb 570

Plant mt. DNA • In addition to larger size, plant mt. DNA are characterized

Plant mt. DNA • In addition to larger size, plant mt. DNA are characterized by molecular heterogeneity. • Large duplications are readily created and lost. Plant mt. DNAs contain at least one large (1 -14 kb) repeated sequence. There is no pattern to the sequences (including genes) that are duplicated in the mitochondrial genomes of different plants.

Plant mt. DNA • Recombination between repeats creates a complex, multipartite genome structure. All

Plant mt. DNA • Recombination between repeats creates a complex, multipartite genome structure. All of the large repeats found in plant mt. DNAs appear to be engaged in high-frequency inter - and intra-molecular recombination.

Plant mt. DNA Tricircular structure of the Brassica campesteris mitochondrial genome

Plant mt. DNA Tricircular structure of the Brassica campesteris mitochondrial genome

Plant mt. DNA • mt. DNA contains short dispersed (50 -1000 bp) repeats scattered

Plant mt. DNA • mt. DNA contains short dispersed (50 -1000 bp) repeats scattered throughout the genome. • mt. DNA contains many foreign sequences. cp. DNA sequences of all kinds (labelled as C 111), some as large as 12 kb in length, are found integrated in plant mt. DNA.

Plant mt. DNA • Plant mt. DNAs change very slowly in nucleotide sequences. Rates

Plant mt. DNA • Plant mt. DNAs change very slowly in nucleotide sequences. Rates of nucleotide substitutions are 3 -4 times lower in plant mt. DNA than in cp. DNA, 12 times lower than in plant nuclear DNA, and 40 -100 times lower than in animal mt. DNA. • Plant mt. DNAs rearrange very rapidly. No two eximined species of flowering plants have the same gene order. Even closely related species differ by one or a few large inversions, whereas the genomes of more distantly related species are virtually randomized with respect to sequence arrangement.

Animal mt. DNA • Animal mt. DNAs are relatively smaller than the plant mt.

Animal mt. DNA • Animal mt. DNAs are relatively smaller than the plant mt. DNAs. • The genome size is more conserved.

Comparison Genome Size of Animal mt. DNA Animal species mt. DNA Aedes aegypti Alligator

Comparison Genome Size of Animal mt. DNA Animal species mt. DNA Aedes aegypti Alligator sinensis Apis mellifera Boa constictor Elephas maximus Gallus gallus Homo sapiens Octopus ocellatus Pongo pymaeus Rana nigromaculata 16. 7 kb 16. 3 kb 18. 9 kb 16. 8 kb 16. 6 kb 16. 4 kb 17. 8 kb

Human Mitochondrial Genome Human mt. DNA composes of a control region (CR), genes encoding

Human Mitochondrial Genome Human mt. DNA composes of a control region (CR), genes encoding 2 r. DNAs (12 S and 16 S), 22 t. RNAs (open circles), 13 polypeptides.

Animal mt. DNA • Non-recombination. • Contains less non-coding sequences. • Higher base substitution

Animal mt. DNA • Non-recombination. • Contains less non-coding sequences. • Higher base substitution rate (even higher than the nuclear DNA regions). • Gene order/structure is more conserved (stable).

mt. DNA in Plant Systematics • Mitochondrial DNA regions commonly used for plant systematics:

mt. DNA in Plant Systematics • Mitochondrial DNA regions commonly used for plant systematics: cox. I, nad 2, atp. A, cob, cox. III, 18 S, 26 S etc. • The high rates of rearrangements and low rates of point mutations make mt. DNA essentially worthless for the restriction site-based reconstructions of intrafamilial phylogeny for which cp. DNA is so well suited. • The occasional losses of mitochondrial genes and introns may also serve as useful markers of phylogeny. • The low rate of mt. DNA substitutions suggests that comparative sequencing efforts will be most rewarding at higher phylogenetic levels.

mt. DNA in Animal Systematics • RFLP on the whole mitochondrial genome is common

mt. DNA in Animal Systematics • RFLP on the whole mitochondrial genome is common in molecular systematics in animals. (involves the isolation of mt. DNA from total DNA) • DNA sequencing is done on variable regions such as D-loop region (control region), cytochrome b, cytochrome oxidase III, 16 S, 12 S etc.