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Copy of Evolution Of Organelles
Transcript of Copy of Evolution Of Organelles
Peroxisomes are small, single membrane bound organelles (<2μm) that appear in all eukaryotic cells. Peroxisomes lack a genome and thus selectively import their needed proteins from the cytosol and some from the endoplasmic reticulum. The defining characteristic of peroxisomes is the presence of oxidative enzymes such urate oxidase and catalase, that are used to break down hydrogen peroxide.
Full Text Article: http://goo.gl/obj5s NUCLEOLUS There is currently a dispute between how peroxisomes evolved. There are 2 main arguments: 1) The Endosymbiotic Theory - This theory states that peroxisomes developed after an endosymbiotic relationship was formed between a bacterial cell and a larger cell, the peroxisome originally invading as a parasite. Proof:
- The protein content of peroxisomes is very similar to that of certain bacterial species
- Peroxisomes replicate via division of old peroxisomes and import some proteins post-translationally, features shared with
mitochondria, who have endosymbiotic origins.
- Proto-peroxisomes may have been ingested at a time when oxygen levels where rising and toxic to cells, hence the proto-peroxisome was utilised by the larger cells to detoxify the compounds. Theory 2) states that peroxisomes evolved from the ER. A more recent theory pointing to the tight relationship between peroxisomes and the ER, originally observed via an electron micrograph. Proof:
- Pex-Proteins are vital in peroxisomal biogenesis and maintenance
- They show homology with the ERAD pathway, the ER’s degradation pathway
- Hints at an evolutionary relationship - The ER most likely originated at the same time as the Nucleus due to the fact that they are continuous with one another. - Cloning of an ER gene from G.Lamblia (an early protozoan) shows that the ER originated very early in the eukaryotic cell. - Theories have suggested that the eukaryotic cell originated from a fusion event between a gram negative bacterium and an early archeabacterium. - It could be drawn from this that the infolding of the membrane of the bacterium around the archeabacterium led to the creation of the ER. (Gupta 1998) THE CELL (cc) photo by medhead on Flickr Peroxisomes have numerous functions: - Breakdown of hydrogen peroxide
- Detoxification of harmful compounds
- Oxidation of fatty acids
- Metabolise nitrogen containing compounds. Mitochondrion
An organelle that is the site of aerobic respiration and ATP generation in eukaryotic cells. Structure: "It is surrounded by two membranes, the inner one much convoluted and carrying respiratory electron transport chains and ATP synthases. The mitochondrial matrix enclosed by the inner membrane contains the enzymes of the tricarboxylic acid cycle. Mitochondria contain a small circular DNA that specifies tRNAs, rRNAs and some mitochondrial proteins" But, how did it evolve? The origin of mitochondria and plastids are very similar. Mitochondria are believed to be 2 billion years old whereas plastids are 1.5 billion. The current leading consensus, to evolutionary biologists, is that mitochondria and chloroplasts started life outside the modern eukaryotic cell (chloroplasts as cyanobacteria and mitochondria as proteobacteria) and was engulfed by another cell. This is the endosymbiotic theory. Most modern work on molecular evolution uses the endosymbiotic theory as groundwork. Evidence:
When the proteobacteria Rickettsia prowazekii had it's DNA sequenced it was found that the enzymes in it's TCA cycle and electron transport chain are phylogenetically related. This shows that they had a common ancestor. 2. Syntrophic model There was an endosymbiotic relationship in which ancient methanogenic archea was incorporated into the cytoplasm of myxobacterium, leading to the formation of the nucleus. The symbiotic relationship came about as the bacteria produced hydrogen ions and the archea used the hydrogen ions, so the two were supporting each other. According to the theory there were two selective forces which aided the formation of nucleus and nuclear envelope. The first being metabolic compartmentation to avoid deleterious co-existence of the anabolic pathway from the catabolic pathways. The second selective force was protection again aberrant protein synthesis. This model almost combines together the fusion theories and autogenous theories as it is thought that the nuclear membrane and ER are derived from the myxobacterium plasma membrane.
Supported by the fact that bacteria and archea have similar proteins such as histones and that myxobacterium contain kinases and G-roteins similar to eukaryotes. 1. Viral eukaryogenesis This theory states that the first nucleus came from a endosymbiotic relationship of a large DNA virus with a proteobacteria and an archea. Originally a cell wall-less archea formed a syntrophic relationship with an alpha-proteobacteria. A complex virus then lysogenized the host resulting in a three way syntrophic relationship. The virus then gained essential genes from the host cell, with the proteobacteria eventually losing many of its genes and the archea losing all its genes. It is believed that the archea then evolved to become the cell cytoplasm.
Virus that supposedly infected the bacteria/archea is believed to be from NCLDV(nucleo-cytoplasmic large DNA viruses e.g. poxviruses) group of viruses. These virus's are double stranded, posses tandem DNA repeats at their telomeres, have mRNA capping and polyadenylation, have linear chromosomes. All of which are characteristics of the eukaryotic genome, which helps prove the viral eukaryogenesis theory. Evolution of the nucleus The evolution of the nucleus, like all organelles, has been the subject of much research for many years. Even now scientists can’t agree on the correct theories. However, I will present to you the four current main theories and the evidence associated with them.
Four main models:
- Viral eukaryogenesis
- Syntrophic model
- Exomembrane hypothesis
- Proto-eukaryotic cells evolved from bacteria without an endosymbiotic stage Function of the nucleus All eukaryotic cells contain a nucleus which stores their genetic information in the form of DNA.
There are 2 main functions:
- Replication: – identical copying of DNA to be passed onto new cells, generation to generation.
- Transcription: – Converting DNA into RNA to allow the genes to be expressed in the cells Nucleus structure Nucleus is separated from the cytoplasm by the nuclear envelope which is a double layer phospolipid membrane. The two membranes are separated by 10-50nm. A thin filamentous layer of lamin polypeptides makes up the nuclear lamina which provides mechanical support to the nuclear envelope. The two layers can be fused at certain points to form protein complex’s which act as nuclear pores.
Within the nucleus the chromosomes can be found which in an interphase cell are in the form of chromatin. These chromosomes are where the genetic information for a self is stored in the form of DNA.
The nucleus also contains at least 1 nucleolus which is an electron dense region that's function is to make rRNA and the assembly of ribosomes.
The solutes which are made in the nucleus are all dissolved into a fluid substance called the nucleoplasm which is all held together by the fibrillar nuclear matrix. The Evolution of the Nucleus Conclusion It is obvious, that even now no one is fully sure on the exact origins on the nucleus. However all of the models have some form of evidence which they are based on, so it is really a matter of opinion which model you believe.
I think that the evidence for viral eukaryogenesis is strongest so that is the model I choose to believe. Fairly recent theory based on evidence from modern planctomycetes bacteria. The genus Gemmata obscuriglobus contain a nucleoid which is enveloped in 2 membranes which are largely similar to the nuclear membrane of eukaryotic cells. Suggests an evolutionary link between their nucleoid and the modern day nucleus with its 2 cellular membranes making up the outer envelope. 4. Proto-eukaryotic cells evolved from bacteria without an endosymbiotic stage 3. Exomembrane hypothesis Suggests that the nucleus developed from a single ancestral cell containing a single strand of DNA which attached to nuclear membrane invaginations. The cell then developed a second membrane around it, with the first membrane becoming the nuclear membrane. At first the newly engulfed cell (like all cells) contained it's own DNA. Modern mitochondrial DNA (mtDNA) encodes some proteins and RNA sequences that are crucial for the structure and function of the mitochondria. As the endosymbiont continued to live, the genome was reduced. Genes coding for various pathways and processes were either removed or complemented by host functions coded in the nuclear DNA. What is the Golgi apparatus?
The Golgi apparatus is an ancient (around 2 billion years old) organelle, which is essentially the ‘post office’ of the cell. How is it like a post office?
The Golgi apparatus receives newly synthesised proteins at the cis-face from the endoplasmic reticulum. As these proteins move through the Golgi Stacks it is unpackaged and then re-packaged into a new vesicle. Finally the protein leaves the Golgi apparatus at the trans-face.
From there it is then sent on to it's final destination of the cell, be it the mitochondria, chloroplast, back to the nucleus or to the plasma membrane along the cell cytoskeleton.
Hence it is like the post office of the cell. Cis-face Trans-face How did it evolve?
It is thought that the Golgi apparatus evolved in a similar way to the endoplasmic reticulum:
Invaginations of the outer-membrane caused by an early nucleus were created in order to produce and distribute proteins coded for by the early nucleus of the proto-eukaryotic cell. It is thought that these invaginations in the outer membrane of the proto-eukaryotic cell occurred in a similar way to the specialisation of a pro-plastid's to form chloroplasts. This process of the outer cell membrane invaginating into the cell to form a chloroplast from a pro-plastid is demonstrated in this figure... Endosomes are membrane-bound compartment inside eukaryotic cells. They are a compartment of the endocytic membrane transport pathway from the plasma membrane to the lysosome. Molecules internalized from the plasma membrane can follow this pathway all the way to lysosomes for degradation, or they can be recycled back to the plasma membrane. Molecules are also transported to endosomes from the Golgi and either continue to lysosomes or recycle back to the Golgi. Rab 7 protein structure, bound to GDP - Endosomes are likely to have originated from the same place as other endomembrane organelles, i.e. the Golgi, lysosomes and the ER, as these are all membrane bound organelles.
- The protein Rab 7 is important in endosomes because it regulates traffic from early to late endosomes and from late endosomes to lysosomes. This protein can be traced to pre-eukaryotic ancestors, which suggests that endosomes have been membrane bound compartments from very early on in the evolution of eukaryotic cells. . -Lysosomes, like many of the other discussed organelles, are likely to have evolved as a result of the plasma membrane going through invagination.
-These invaginations may have led to the specialization of internal membranes.
-In the early parts of eukaryotic cell life these invaginations may have been attached to and interconnected to the plasma membrane.
-As the cells functions diverged the membranes may have become separate structures / organelles e.g. lysosomes. If you're still interested in finding out more about the evolution of organelles, then take a look at some of the interesting links below for further reading and interactive material: Animation with narration: http://www.sumanasinc.com/webcontent/animations/content/organelles.html
Detailed webpage explaining mitochondrial and chloroplast genomics with a small section about potential secondary symbiosis: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Endosymbiosis.html
Wiki page with useful diagrams and explanations of Lynn Margulis' theory of endosymbiosis:
http://fhs-bio-wiki.pbworks.com/w/page/24612814/Endosymbiotic%20theory Learning Outcomes of our Presentation:
-•To understand the origin and evolution of the major sub-cellular organelles
-•Learn the basic principles behind the endosymbiosis theory
•-To gain a better understanding of the structure of the described organelles
-•Understand the function of the major sub-cellular organelles REVISION QUESTIONS! 1) What is the name given to the process by which most scientists believe the mitochondria and chloroplast became part of the cell?
2) Which scientist first pioneered this theory?
3) What are the four main theories associated with nuclear evolution?
4) What is the term that describes the evolution of the eukaryotic cell with the endoplasmic reticulum and the nucleus forming at the same time?
5) Outline the two theories regarding peroxisome evolution. Here is a fantastic video summarising the endosymbiosis theory. Credit to Paul Andersen at Bozeman High School, Massachusetts. www.youtube.com/watch?v=-FQmAnmLZtE The evolution of the chloroplast is almost identical to that of the mitochondria. Theory states that they both came about by endosymbiosis and moved most of their genome to the nuclear DNA. For more information you can read: http://www.ncbi.nlm.nih.gov/books/NBK28410/ As with every theory in science, there is no definite right or wrong. Science is a collaboration and although we present the best evidence possible at the time... ... THERE COULD BE SO MUCH MORE TO DISCOVER! R Functions of the lysosome -The ER is a series of flattened tubules that manafactures membranes and secretory proteins such as insulin.
-It can be classified into two different types:
Rough ER is studded with ribosomes
Smooth ER has no ribosomes and is responsible for a number of functions such as production of sex hormones in the brain. REFERENCE LIST Abhishek, A. et al. (2011). Bacterial genome chimaerism and the origin of mitochondria. Canadian Journal of Microbiology, 57: 49-61.
Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., Walter, P. The Compartmentalizing of Cells. In: Molecular Biology of the Cell. 4th ed. New York: Garland Science.
Bell, P.J. (2001). Viral eukaryogenesis: was the ancestor of the nucleus a complex DNA virus?. Journal of Molecular Evolution 53: 251-256.
Bell, P.J. (2009). The viral eukaryogenesis hypothesis. Natural Genetic Engineering and Natural Genome Editing 1178: 91-105.
Brighouse, A ., Dacks, J., Field, M. (2010). Rab protein evolution and the history of the eukaryotic endomembrane system . Cellular and Molecular Life Sciences. 67: 3449-3465.
Choi, J. W., Lee, J. S., Kim, S. W., Yun, C. O. (2012). Evolution of oncolytic adenovirus for cancer treatment. ,Advanced Drug Delivery Reviews. 64: 720-729.
Claverie, J. M. (2006). Viruses take center stage in cellular evolution. Genome Biology 7: 110.
Dacks, J., Peden, A., Field, M. (2009). Evolution of specificity in the eukaryotic endomembrane system. International Journal of Biochemistry and Cell Biology 41: 330-340.
Duhita, N., Thuy, L. H. A., Satoshi, S., Kazuo, H., Daisuke, M., Takao, S. (2009). The Origin of Peroxisomes: The Possibility of an Actinobacterial Symbiosis. Gene 450: 18-24.
Felder, S., Miller, K., Moehren, G., Ullrich, A., Schlessinger, J., Hopkins, C. R. (1990). Kinase activity controls the sorting of the epidermal growth factor receptor within the multivesicular body. Cell 61: 623–34
Fuerst, J.A. (2005). Intracellular compartmentation in planctomycetes. Annual Review of Microbiology 59: 299-328.
Fuerst, J.A. (2010). Beyond prokaryotes and eukaryotes: planctomycetes and cell organization. Nature Education 9: 44.
Gabaldon, T. (2009). Peroxisome Diversity and Evolution. Philosophical Transactions of the Royal Society of Biological Sciences 365: 765-773.
Gabaldon, T., Snel, B., Zimmeren, F.V., Hemriker, W., Tabak, H., Huynen, M.A. (2006). Origin and Evolution of the Peroxismal Proteome. Biology Direct 1: 8-22.
Gould, S. et al. (2008). Plastid Evolution. Annual Review of Plant Biology 59: 491-517.
Gupta, S. Protein Phylogenies and Signature Sequences: A Reappraisal of Evolutionary Relationships among Archaebacteria, Eubacteria, and Eukaryotes, Microbiol Mol Biol Rev (1998) December, 62: 1435-1491.
Lodé, T. (2012 )For quite a few chromosomes more: the origin of eukaryotes. Journal of molecular biology
López-García, P. and Moreira, D. (2006). Selective forces for the origin of the eukaryotic nucleus. Bioessays 28:525-533.
Luzio, J.P., Rous, B.A., Bright N.A., Pryor P.R., Mullock B.M. and Piper R.C. (2000). Lysosome-endosome fusion and lysosome biogenesis. Journal of Cell Science 113: 1515–1524
Margulis, L. (2008). Origin of Mitochondria and Hydrogenosomes. History and Philosophy of the Life Sciences 30: 473-477.
Margulis, L., Dolan, M.F., Guerrero, R. (2000). The chimeric eukaryote: origin of the nucleus from the karyomastigont in amitochondriate protists. Proceedings of the National Academy of Sciences 97: 6954-6959.
Rak, A., Pylypenko, O., Niculae, A., Pyatkov, K., Goody, R.S., Alexandrov, K. (2004). Structure of the Rab7/REP-1 complex: insights into the mechanism of Rab prenylation and choroideremia disease. Cell 117: 749-760 .
Richards, T.A. et al. 2011. Cell Evolution: Gene Transfer Agents and the Origin of Mitochondria. Current Biology 24: 112-114.
Roos, A.D. (2006). The origin of the eukaryotic cell based on conservation of existing interfaces. Artificial Life 12: 513-523.
Schluter, A., Fourcade, F., Ripp, R., Mandel, J.L., Poch, O., Pujol, A. (2006). The Evolutionary Origin of Peroxisomes: an ER-Peroxisome Connection. Molecular Biology Evolution. 23: 838-845 HOW TO USE THIS RESOURCE 1. Follow the preset path that we have layed out for you by using the forward and backwards arrows at the bottom of the screen. 2. If you wish to focus on one specific organelle, or wish to bypass certain areas of the resource, simply click which ones you wish to view and you will be taken to the information you desire. 3. Don't forget that you can explore the our resource at your own leisure. You can zoom in and out using the scroll wheel on your mouse and move around by clicking and dragging the screen. If you find your screen disorientated then you can revert to the original view by scrolling back to the first path screen, or by clicking onto a body of text which will automatically re-orientate the screen with that text. Introduction
This Prezi presentation aims to set out in a clear and concise manner how the organelles of a cell have developed and evolved. The Prezi is set out in a logical structure that allows the user to navigate the site in an organised fashion, discovering more about the organelles of their choice.
They key sections of this Prezi are:
- Mitochondrial and Chloroplast Evolution
- Lysosome and Endosome Evolution
- The Evolution of the Peroxisome
- The formation of the ER
- Nucleus Evolution
- Golgi Apparatus Evolution
- Extra-reading, Revision and References. The evolution of organelles has been subject to research for many years, the endosymbiotic hypothesis was first proposed in 1910 by Konstantin Mereschkowski, a Russian botanist. Ever since, scientists have been debating the origins of the various organelles and even to this day there are still many unknowns.
This link provides a nice introduction to the field of evolution of organelles.
Full Text Article: http://goo.gl/13qb3 Full Text Article: http://goo.gl/xq79F