1. Plant of the Day! Rafflesia arnoldii (Euphorbiaceae)
Parasitic (host Tetrastigma)
No stems, leaves or true roots
Largest single flower (>1 m, 10kg)
Corpse flower, diclinous
1/100 flowering plants are parasitic
HGT can occur between parasites and hosts
Plant of the Day!
Observation: Plants larger in invasive range with increased RO and may be the reason my they spread rapidly in the invaded range . 1

2. Organelle Genome Evolution
Describe the origin of the organelle genomes
Describe the evidence for gene transfer between the organelle and nuclear genomes and discuss hypotheses concerning the mechanism of gene transfer
Discuss hypotheses concerning the maintenance of organelle genomes
Observation: Plants larger in invasive range with increased RO and may be the reason my they spread rapidly in the invaded range . 2

3. endosymbiotic theory
>1.5 billion years ?
The mitochondria: evolved from aerobic bacteria (α- proteobacteria- rickettsias) and a host
The chloroplasts: evolved from a heterotrophic eukaryote and a cyanobacteria
Observation: Plants larger in invasive range with increased RO and may be the reason my they spread rapidly in the invaded range . 3

4. Evidence for Endosymbiotic Theory
-Circular molecule No histones Protein synthesizing machinery (ribosomes, tRNA, rRNA) Some antibiotics block protein synthesis within the mitochondria and chloroplasts Structurally similarity Reproduce through fission
-Strong phylogenetic evidence
Observation: Plants larger in invasive range with increased RO and may be the reason my they spread rapidly in the invaded range . 4

5. Primary endosymbiosis
Plant ancestor
Primary endosymbiosis
Primary endosymbiosis
amoeba
Secondary endosymbiosis
Secondary endosymbiosis
Secondary endosymbiosis
Tertiary endosymbioses
Tertiary endosymbiosis
Keeling 2004

7. Plant chloroplasts

8. Structure of Plant cp Genomes
LSC – 84 kb
SSC – 18 kb
IR – 25 kb (each))
Dempewolf et al., 2010

9. Gene transfer and comparative analysis
Comparisons of nuclear, organelle and candidate prokaryotic ancestor genomes?
-Ancient transfer events
Comparison of organelle genes and nuclear genes of the same species?
-Recent transfer events

10. Chloroplast Gene Transfer
NUPTS (nuclear plastid DNA) :
Arabidopsis has 11kb from 17 insertions
rice chromosome 10 has a 33kb and a 131kb insertion and 26 more over 80bp each

11. Chloroplast Gene Transfer
InfA (translation initiation factor) transferred to nuclear genome (~24x)
Mutational decay/loss of cp sequence
~18% of protein coding genes in Arabidopsis are from the plastid
(transit peptide coding region)
Endosymbiotic gene replacement
Millen et al 2001

12. Chloroplast Gene Transfer
Rate estimates from tobacco chloroplasts
1 transfer in 5 million leaf cells
1 transfer in pollen grains
Higher rates of transfer in the pollen?
Degradation of the organelle genomes in pollen could make DNA fragments available for uptake

13. Plant mitochondria
kbp # protein coding genes

14. Wheat mtDNA
452,528 bp

15. Observation: Plants larger in invasive range with increased RO and may be the reason my they spread rapidly in the invaded range .
Plant mitochondrial genomes undergo intra- or intermolecular recombination via repeated sequences subgenomic molecules (loop out) or isomeric forms (flip flop) 15

16. Mitochondrial Gene Transfer
NUMTS:
complete mt genome sequences in cat nuclei
>296 in humans, from 106 to kbp each (older NUMTs more abundant-tandem repeats)
rice chromosome 10 has 57 NUMTS ranging from bp
Observation: Plants larger in invasive range with increased RO and may be the reason my they spread rapidly in the invaded range .
Do larger nuclear genomes have more NUMTS? 16

17. Mitochondrial Gene Transfer
rate estimates:
1 plasmid transfer to nucleus in 20,000 yeast cells
(integration rare)
Observation: Plants larger in invasive range with increased RO and may be the reason my they spread rapidly in the invaded range . 17

18. Mitochondrial Gene Transfer
Evidence for parallel transfer and loss
e.g. rps10 gene independently transferred to nucleus numerous times
Observation: Plants larger in invasive range with increased RO and may be the reason my they spread rapidly in the invaded range .
Adams et al 2000 18

19. Mechanisms
Bulk DNA – recombination between escaped organelle DNA and nuclear DNA
Expt. transfer in yeast
Non-coding sequence frequently transferred
Whole organelle sequences transferred
MUST HAPPEN
cDNA intermediates
Nuclear copies of organelle genes often lack organelle-specific introns and edited sites
MAY HAPPEN
Observation: Plants larger in invasive range with increased RO and may be the reason my they spread rapidly in the invaded range . 19

20. Why are the organelle genomes maintained?
Hydrophobicity -hydrophobic proteins are poorly imported (excess of membrane embedded proteins)
Fitness advantage if coding sequence and regulation are in same location
Other constraints (e.g. RNA editing, genetic code)
Observation: Plants larger in invasive range with increased RO and may be the reason my they spread rapidly in the invaded range . 20

21. Observation: Plants larger in invasive range with increased RO and may be the reason my they spread rapidly in the invaded range . 21

22. Observation: Plants larger in invasive range with increased RO and may be the reason my they spread rapidly in the invaded range . 22