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Algal Evolution

Algal Evolution. Johanna Weston . Keeling, 2004. 3.5 billion cyanobacteria 2.2 to 1.5 billion mitochondial origin 1.5 – 1.2 Plastid “Little Green Slaves”. ENDOSYMBIOSIS Primary Secondary Tertiary Serial Secondary. How do endosymbionts become organelles?.

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Algal Evolution

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  1. Algal Evolution Johanna Weston Keeling, 2004

  2. 3.5 billion cyanobacteria • 2.2 to 1.5 billion mitochondial origin • 1.5 – 1.2 Plastid • “Little Green Slaves” (Dyall et al., 2004)

  3. ENDOSYMBIOSIS • Primary • Secondary • Tertiary • Serial Secondary (Keeling, 2004)

  4. How do endosymbionts become organelles? • Organelle – discrete subcellular structure of specialized function usually bound by two or more membranes • Metabolite antiporters and Biochemical pathways • Genetic integration and reduction • Protein import apparatus

  5. Phosphate Translocator Family • Antiport dependent on counter-exchange • Algae profit from cyanobacteria carbon fixation • ER/Golgi metabolite translocator protein in host recruited to the plastid envelope (Bhattacharya et al., 2007)

  6. Transfer and Reduction • Cyanobacteria • 2000 to 4000 kb • Plastids • < 200 kb • < 200 genes • “Muller’s ratchet” • Oxygen free radials (Bhattacharya et al., 2007)

  7. TIC - TOC C N Transit peptide • Defining feature of organelle genesis • Sophisticated outcome of the requirement for regulated protein import • Evolutionary diverse origins • Cyanobacteria • Co-option of host genes • HGT from bacteria (Gould et al., 2008)

  8. TIC-TOC Independent • Existing endomembrane system of host cell • Paulinellachromatophora • α – carbonic anhydrase • **2o Endosymbiosis combination of both (Gould et al., 2008) (Bhattacharya et al., 2007)

  9. Animal-Algal Endosymbiosis • Elysiachloroticaand chloroplasts of Vaucherialitorea • 9 months with only light and CO2 • Not inherited (Mujer et al., 1996) (Green et al., 2000)

  10. References • Bhattacharya, Debashish, et al. "How do endosymbionts become organelles? Understanding early events in plastid evolution." BioEssay (2007): 1239-1246. • Gould, Sven, Ross Waller and Geoffrey Macfadden. "Plastid evolution." Annual Review of Plant Biology (2008): 491-517. • Graham, Linda E., James M. Graham and Lee W. Wilcox. Algae. 2. San Francisco: Benjamin Cummings, 2009. • Green, Brian, et al. "Mullusc-algal chloroplast endosymbiosis. Photosynthesis, thylakoid protein maintenance, and chloroplast gene expression continue for many months in the absence of the algal nucleus." Plant Physiology (2000): 331-342. • Keeling, Patrick. "Diversity and evolutionary history of plastids and their hosts." Americal Journal of Botany (2004): 1418-1493. • Mujer, Cesar, et al. "Chloroplast genes are expressed during intracellular symbiotic association of Vaucherialitoreaplastids with the sea slug Elysiachlorotica." Cell Biology (1996): 12333-12338. • Weber, Andreas, Marc Linka and Debashish Bhattacharya. "Single, ancient orgin of a plastid metabolite translocator family in Plantae from an endomembrane-derived ancestor." Eukaryotic Cell (2006): 609-612.

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