|Lane N (2010) Mitochondria and the origin of complex life. Abstract MiP2010.|
Lane N (2010)
The discoverer of mitochondria, Richard Altmann, saw his 'bioblasts' as the elementary particles of life, the unique life-givers of all complex organisms. His ideas were ridiculed and forgotten, until revived by Lynn Margulis in the 1960s. But Margulis's serial endosymbiosis hypothesis actually diminished the importance of mitochondria, reducing them to one among many putative endosymbionts. This view is largely consonant with mainstream medical research, which sees eukaryotic cells as complex systems in which the mitochondria are important, but no more than, say, the endoplasmic reticulum. But over the last decade the focus has shifted again and it has now become clear that the origin of the eukaryotic cell was a unique event that occurred just once in the 4-billion-year history of life. The eukaryotic cell was founded in a singular endosymbiosis between two prokaryotes, an archaeon and the bacterial ancestor of mitochondria. This perspective illuminates the role of mitochondria in the life and death of cells, for example in apoptosis. But there is a deeper question about the role of mitochondria in spawning the evolution of complexity. Prokaryotes show essentially no propensity to evolve morphological complexity, but the acquisition of mitochondria transformed a prokaryote into a eukaryote. The basis of this transformation has remained unclear: it is not related to aerobic respiration, protection against oxygen toxicity, or compartmentalisation, as prokaryotes are adept at all three. I shall present new evidence that mitochondria revolutionised bioenergetics, providing enough energy to support genomes 200,000 times larger than prokaryotes. The critical difference between prokaryotes and eukaryotes, the basis of all complex life, is the extreme genomic polarization of eukaryotic cells, with giant nuclear genomes supported by thousands of tiny mitochondrial genomes. Without mitochondria, and specifically without their tiny contingent of genes, complex life could not exist. These principles of bioenergetics should apply throughout the universe. Altmann would surely have approved of the clear prediction (testable in principle): aliens will have mitochondria too.
Nick Lane is author of:
1. Oxygen: The Molecule that Made the World (2002) Oxford Univ. Press.
2. Power, Sex, Suicide: Mitochondria and the Meaning of Life (2005) Oxford Univ. Press.
3. Life Ascending: The Ten Great Inventions of Evolution (2009) Norton.
Labels: MiParea: Respiration
Stress:Ischemia-reperfusion Organism: Eubacteria, Archea
Coupling state: OXPHOS
mtDNA, Endosymbiosis, Evolution
- Life Ascending won the Royal Society Prize for Science Books, 2010!