Eukaryotism Reconsidered
Herrmann, R.G.
Botanisches Institut der Ludwigs-Maximilians-Universität, Menzinger Str. 67,
D-80638 München, Germany
Eukaryotic cells, and implicitly their genomes are beyond reasonable doubt the results of endocytobioses, and, strictly speaking, phylogenetic curiosities. They originated in conglomerates of cells, two in animals and three, four or even five in plants, arisen through the incorporation of bacterial or, in the case of plastids, also of unicellular eukaryotic cells (microalgae) into a host organism. These cell conglomerates developed a common metabolism, a common inheritance, and concomitantly an integrated, compartmentalized genetic system (rather than semiautonomy of organelles). The genetic compartments are represented by nucleus/cytosol and the energy-transducing organelles: mitochondria in animals, mitochondria and plastids in plants. The integration of mitochondria and chloroplasts with their respiratory and photosynthetic potential respectively, was probably forced by environmental changes and accompanied by a colossal restructuring of genetic information within that cell. This led to the dual genetic origin of complex organelle structures and to the establishment of novel intercompartmental regulatory circuitries. Cellular cohabitation had obviously an enduring impact to the evolution of life. Only the complex eukaryotic genomes permitted the development of advanced (true multicellular) forms of life with an enormous morphogenetic potential, in combination with oxygenic photosynthesis also of terrestrial life. In the plant kingdom, this potential is evident spatially and temporally, from algae, mosses to vascular plants with their complex generation cycles. - The phylogenetic-comparative molecular approach has caused a fundamental conceptual change in the way we view living matter, and provided the outlines of a natural genealogy of plants as well as first steps towards a functional molecular phylogeny. Comparison of plastids and mitochondria/hydrogenosomes, and the study of translocated, now nuclear genes has provided evidence for a hierarchy of gene translocations, for the kinetics of gene rearrangements that were not unidirectional, that pathways are phylogenetic mosaics with eubacterial dominance, and a general two-step evolution of eukaryotes.
Supported by the Deutsche Forschungsgemeinschaft (SFB 184) and the Human Frontier Science Program.
Herrmann, R.G. (1997) Eukaryotism, towards a new interpretation. pp. 73-118. In: Eukaryotism and Symbiosis. Springer Berlin, Heidelberg, New York.
Kowallik, K.V. (1997) Origin and evolution of chloroplasts: Current status and future perspectives. pp. 3-23. In: Eukaryotism and Symbiosis. Springer Berlin, Heidelberg, New York.
| LOCATION |
DATE |
TIME |
| Lecture Hall I |
Monday, April 6 |
11:30 am |