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Ralf Sommer – his fascination with species diversity is at the heart of his career

From filigree butterflies to pot-bellied bugs – Professor Dr. Ralf J. Sommer has always had such a fascination with the biological diversity of species that he eventually decided to turn his hobby into a profession. When he was at university many years ago, the current director of the Tübingen-based Max Planck Institute for Developmental Biology left no stone unturned in his attempts to decipher the mechanisms that enable nature to bring about new species. An exotic threadworm from an island in the Indian Ocean is now helping him solve some of the most exciting evolutionary puzzles.

Prof. Dr. Ralf. J. Sommer © private

As a schoolchild, Ralf J. Sommer, who was born in Würselen, had a hobby that has since become a great deal less fashionable - butterfly collecting. "I wanted to collect bugs, but my mother was not too keen on the idea. So I decided to collect butterflies instead," recalls the 46-year-old director of the Tübingen-based Max Planck Institute (MPI) for Developmental Biology with a smile.

He spent hours and hours learning the nomenclature of the colourful insects, and how to identify and classify them. "My classmates thought I was a bit of a freak," admits Sommer frankly. At the time, Sommer had no way of knowing that his exotic hobby was the starting point of what would later become his profession. "Now I know quite a few MPI directors who used to get excited about a particular group of animals or plants when they were children.

Despite his enthusiasm for classical zoology, Sommer nevertheless decided to focus on molecular biology very early on during his biology studies. That is why he moved from Aachen to Tübingen, where developmental genetics was a strongly emerging science at the beginning of the 1980s, and from there to the LMU in Munich. "I always moved to places where I could do what interested me most," said Sommer explaining his moves from one university to another. This single-mindedness has paid off. During his doctoral studies at the LMU in Munich, Sommer began focusing on the evolution of developmental processes in insects, a topic that enabled him to combine molecular biology and his childhood interests in a way that suited him.

No one worm is like another

Sommer has never been interested in medical research. “This is maybe because I am part of a generation who discovered that the majority of genes are highly conserved,” said Sommer explaining that fly, worm and human genes do not differ that much from one another. He has never been part of the rush to use these animals as model organisms for human diseases. “I found this approach far too simple,” said the researcher going on to add “functional biology is very different from physics, which deals with superordinate regularities.” Sommer is convinced that all organisms are the unique product of a variety of independent evolutionary processes.

Sommer found initial evidence for his reservations while he was working with threadworms. The worm Caenorhabditis elegans had already been established as a model organism in the laboratory of Paul Sternberg at the California Institute of Technology (CalTech) when Sommer joined the institute as a post-doctoral student. There he worked on Pristionchus pacificus, a close relative of C. elegans, and found that the P. pacificus vulva was made up of exactly the same cells as C. elegans. “However, the underlying process is governed by completely different genes,” said the biologist. This means that the structure of the genes did not change during evolution, whereas the genes’ functions did.

“If we take into account that the development of two related threadworms does not even follow a common mechanism, then we must be very careful when transferring findings gained in Drosophila or worms to the situation in humans,” said Sommer whose views have already sparked off numerous controversial scientific debates.

Developmental genetics in an ecological context

A fascinating organism: Pristionchus pacificus was for the first time ever described in the mid-1990s by Ralf Sommer. © Dr. Ralf Sommer, Max Planck Institute for Developmental Biology

Sommer's scientific focus is directed to the mechanisms that bring about the huge diversity of species in nature, something that he was fascinated by as a schoolchild. The central aspect of his research is the question as to why all organisms have the same molecular blueprint in principle, but nevertheless look very different. Sommer, who made a considerable contribution to deciphering the genome of Pristionchus pacificus in 2008, no longer exclusively focuses on the genetic aspects of developmental biology. Instead, he is to an increasing extent looking at his work in an ecological context. The best example of this is the investigation of the P. pacificus life cycle. "In the laboratory, the P. pacificus life cycle is only three days. In nature, the worms can survive for much longer by associating with scarab beetles as dauer larvae," said Sommer going on to add "where P. pacificus resumes development once the beetle has died".

Sommer will focus his future work on finding out how the worm is able to adapt to its specific living space in such an unusual way. In order to do this, Sommer will combine evolutionary as well ecological and population genetic approaches. Another element of this approach is a particular research branch that was set up on the island of La Reunion (50km x 50 km in size) a couple of months ago. "If you want to find out where differences come from, you have to look at different strains of the same species. And the best place to do this is on an island," said Sommer explaining that "restricted systems found on islands are much easier to investigate." The fact that the genetic differences of different strains of threadworms are as great on La Reunion as elsewhere, is a piece of scientific luck for Sommer. "La Reunion is the perfect microcosm for our work," said Sommer who has already discovered some evolutionary tricks. Sommer and his team have recently shown that certain Pristionchus pacificus signalling pathways have several functions. For Sommer, this is further fascinating evidence of the ingeniousness of evolution.

Further information:

Professor Dr. rer. nat. Ralf J. Sommer
Max Planck Institute for Developmental Biology
Department of Evolutionary Biology
Spemannstr. 35 - 39
72076 Tübingen
Tel.: +49 (7071) 601 441
Fax: +49 (7071) 601 498
E-Mail: ralf.sommer[at]tuebingen.mpg.de

Website address: https://www.gesundheitsindustrie-bw.de/en/article/news/ralf-sommer-his-fascination-with-species-diversity-is-at-the-heart-of-his-career