28 November 2012
Time: 3:00 - 4:00pm
Venue: BR 3.02 Bancroft Road Teaching Rooms Peter Landin Building London E1 4NS
The extraordinary evolution of complex life
The complex eukaryotic cell arose just once in 4 billion years of evolution, in an endosymbiosis between two prokaryotes. All plants, animals, fungi, algae and protists derive from this singular event. The endosymbiotic bacteria evolved to become mitochondria, which retain a tiny genome of their own. I shall argue that eukaryotic genomic and morphological complexity depended on the reductive evolution of the mitochondrial genome, which ultimately produced an extreme genomic asymmetry in complex eukaryotes, in which tiny mitochondrial genomes support, energetically, a virtually unlimited accumulation of DNA in the nucleus, the genetic raw material for the evolution of complexity. But there is a price: a requirement for intergenomic coadaptation. The tempo and mode of evolution of mitochondrial and nuclear genes are radically different, with mitochondrial genes in animals evolving asexually, orders of magnitude faster than the sexually recombining nuclear genes. Modelling shows that two sexes, with the uniparental inheritance of mitochondria, improves mitonuclear coadaptation. In multicellular organisms with germline and soma, mitonuclear incompatibilities lead to free-radical leak from mitochondria, apoptosis, hybrid breakdown and even speciation. The mitochondrial threshold for apoptosis is predicted to vary between species, depending on aerobic requirements, resulting in a fundamental trade-off between aerobic fitness, fertility, adaptability, lifespan and disease.
Biography: Nick Lane is a biochemist and writer. He was awarded the inaugural Provost’s Venture Research Fellowship in the Department of Genetics, Evolution and Environment at University College London. Nick leads the UCL Research Frontiers Origins of Life programme, and is a founding member of the UCL Consortium for Mitochondrial Research. His research is on the role of bioenergetics in the origin of life and the evolution of complex life.