Endosymbiosis and evolution of Organelles

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Endosymbiosis is important as it enables us to understand the evolution of eukaryotes from the common ancestor. This essay will focus on: the early evolution of our eukaryote ancestor during Precambrian period, plastids origin along the algae family due to second endosymbiosis; discuss the evidence that supports the theory, including further examples of endosymbiosis.

The theory, as discussed by Lynn Margulis, states that mitochondria originated from α-proteobacteria bacterium which was engulfed by the ancestral anaerobic eukaryotic cell, through endocytosis, and retained within the cytoplasm due to atmospheric oxygen increase. Prokaryote organism produced ATP, through oxidative phosphorylation, by receiving organic compounds from the eukaryote, causing the eukaryote to become dependent on prokaryote for ATP production and the prokaryote to become dependent on the eukaryote for other cellular functions. Consequently, both organisms evolved in symbiosis with each other and most the genes of a unicellular organism were transferred to the genome of the host, getting enclosed in the nucleus. Due to the advantageous relationship between the host and symbiont, prokaryote organism lost their ability to survive independently and, was reduced into mitochondria which were transmitted to future generation vertically (Debashish et al., 2003). The evolutionary history of plants involves at least two independent endosymbiotic events (as shown in Figure 1); because plastids such as chloroplast evolved when a primary endosymbiotic event caused photosynthetic cyanobacteria to be engulfed by some non-photosynthetic host cells (Dyall et al., 2004).

Chlorophyta, Rhodophyta and Glaucophyta are three clades, belonging to the group Archaeplas...

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...n, P.J., 2004. Ancient Invasions: From Endosymbionts to Organelles. Science, 304 (5668), pp. 253-257.

Lake, J.A., 2009. Evidence for an early prokaryotic endosymbiosis. Nature, 460, pp. 967-971.

McFadden, G. I., 2001.Primary and Secondary Endosymbiosis and the Origin of Plastids. Journal of Phycology, 37(6), pp. 951–959.

Rumpho, M.E., Worful, J.M., Lee J., Kannan, K., Tyler, M.S., Bhattacharya, D., Moustafa, A. and Manhart, J.R., 2008. Horizontal gene transfer of the algal nuclear gene psbO to the photosynthetic sea slug Elysia chlorotica. PNAS, 105(46), pp. 17867-17871.

Smith, A.M., Coupland, G., Dolan, L., Harberd, N., Jones, J., Martin, C., Sablowski, R. and Amey, A., 2010. Plant biology. New York: Garland Science; Taylor & Francis distributor.

Tomitani, A., 2006. Origin and early evolution of chloroplasts. Paleontological Research, 10 (4), pp. 283-297.

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