Günter Theißen: Key innovations in the evolution of flower development

L'Evolution c'est bricolage - Evolution is tinkering - with this famous statement, the French Noble Award Winner Jacob wanted to express that in biology often preexisting phenomena are recombined in a new context. This leads to the question, how "novel" can be defined at all in biology. Especially, when it comes down to the genetic level. Did novel genes fall from sky? Whether something is "novel" is investigated by a central biological technique, the comparative approach (so called homology search). Homologies are crucial for biology, may it bi on the morphological (the wings of the birds are homologous with the arms of humans), may it be on the molecular level (two genes are homologous, when it is possible to arrange them side by side in a so called alignment, where changes in the sequence become evident). Since many bodies are actually composed of rhythmically repeated elements (the segments of arthropods or the shoot nodes of land plants) that are then modulated, the problem of macroevolution can be rephrased - the spatial (or temporal) shift of such a repeat should create results that are not so easily homologisable. In the simplest case, just the number of organs is changing (spiders have eight, insects only six legs, the homology is still easily recognised). However, sometimes qualitative novelty is generated, often by temporal shifts in developmental processes. On the molecular level, genetical switches, so called transcription factors are activated at different times or at different amplitudes. When we want to understand "form", we need to understand, by which processes it is generated and how these processes are ordered in space and time. The history is as important as the result. Flower formation is not only among the best understood morphogenetic processes in terms of developmental genetics, but also a process, where evolution has created in extremely short time incredible variations - already Darwin was puzzled by the "abominable mystery" that so many flowering plants emerged in a geologically short time.

Speaker: Günter Theißen studied in Düsseldorf, where he also did his Ph.D., before taking a group leader position at the Max-Planck-Institute for Breeding Research in Cologen, a location, where the "EvoDevo of flowering" was elucidated. After a short stopover in Münster, he moved 2002 to Jena, where he has been workind since then. He contributed not only important elements to the genetics of flowering by extending the classical ABC model into a widely accepted floral quartet model, but investigated also in primitive Gymnosperms how the novely of a flower actually was generated (by the way also using samples from the Botanical Garden of the KIT). He is known as determined opponent of the creationist movement that is progressively spreading also in Europe after having infested the US. Instead, he tries to explain macroevolution by scientific approaches and models.