uni'wissen 02-2012 ENG

bryonic axis takes shape, with the future shoot cells on the one side and the root cells on the other. If the WUSCHEL-like genes WOX8 and WOX9 are missing, the hormone auxin will not be distributed correctly in the embryo, and only an unstructured cell cluster will be created. “Em- bryo cells are similar to the stem cells – neither of them is specialized yet at this point,” says Laux, “and it is thus possible that the original purpose of WUSCHEL was to develop embryos.” Fundamental Research for High-Yield Forests On the basis of their previous studies, Laux and his team are now working on applications for growing plants by way of embryogenesis rather than through the traditional method of fertiliza- tion. In order to do this, the scientists use either active stem cells or sleeping stem cells, which only awaken in trees if the trunk snaps. If they are provided with nutrients and special hor- mones, these stem cells begin to develop into embryos – much as some plants develop from offshoots of a parent plant. The new embryos can then be planted. “There are various reasons why it is interesting to avoid sexual reproduction, in which the genetic information of the mother and father are mixed,” says Laux. “Somatic embryogenesis enables breeders to preserve particular varieties in a pre- cise state.” One promising effect of this is known as heterosis: “When one crosses two different pure-breed parents, the mixed-breed daughter generation can be particularly bountiful. However, the precise reason for this is one of the great se- crets of plant science.” When the following gen- eration reproduces by way of sexual reproduction, the effect is cancelled out. As increasing the yield of crops is an important goal in many parts of the world, somatic embryogenesis is seen as a promising approach in plant breeding. From Freiburg to China The Freiburg biologists are cooperating with a team from the Chinese University of Nanjing that is studying trees. Their knowledge and their ex- perience with the model plant Arabidopsis is a valuable addition to the project: Somatic em- bryogenesis is actually difficult to achieve in trees, but the biologists can stimulate the trees to produce more stem cells and embryos with Prof. Dr. Thomas Laux studied biology in Erlangen and earned his doctorate in biochemistry. After a pe- riod conducting research in Los Angeles, USA, and Munich, he earned his ha- bilitation at the University of Tübingen. A year later he accepted a position as professor in molecular genetics and biotechnology of plants at the University of Freiburg. From 2008 to 2011 he was a fellow at the Freiburg Institute for Ad- vanced Studies (FRIAS). He is a member of the Cluster of Excellence BIOSS Centre for Biologi- cal Signalling Studies of the University of Freiburg. Together with partners in Strasbourg, France, and Basel, Switzerland, Laux coordinates the trinational degree program Biotech- nology and is involved in the Trinational Institute of Plant Research, estab- lished in 2011 with funding from the European Union. His research interests in- clude developmental biol- ogy and the biotechnology of plants. Laux studies how cellular signals control stem cells and embryonic development and the ways in which they can be artifi- cially influenced. Further Reading Breuninger, H./Rikirsch, E./Hermann, M./ Ueda, M./Laux, T. (2008): Differential expres- sion of WOX genes mediates apical-basal axis formation in the Arabidopsis embryo. In: Developmental Cell 14/6, p. 867–876. Sarkar, A./Luijten, M./Miyashima, S./Lenhard, M./Hashimoto, T./Nakajima, K./Scheres, B./ Heidstra, R./Laux, T. (2007): Conserved fac- tors regulate signalling in Arabidopsis shoot and root stem cell organizers. In: Nature 446, p. 811–814. Laux, T. (2003): The stem cell concept in plants: a matter of debate. In: Cell 113/3, p. 281–283. WUSCHEL. At the same time, the research group is studying how plants can better protect themselves against heavy metals in the ground, which damage the stem cell niches in the roots. “This is a very ambitious project. The various sig- nal substances in the root all combine to make up a big puzzle that we do not yet completely un- derstand.” Through the use of modern methods of analy- sis like life imaging, which makes metabolic pro- cesses visible, the scientists are attempting to identify the various pieces of the puzzle and shed light on the system as a whole. “One stum- bling block is that the WUSCHEL factors also in- fluence a host of other genes,” says Laux. “The relationships are complex since we can always only study one factor that makes a relatively small contribution to the overall system. If all we see is that the plant is not doing well after we have manipulated a genetic switch, we do not yet comprehend the underlying relations. We are thus using many different molecular genetic and mathematical instruments in order to understand each switch one at a time and to unravel the mystery of how plants develop.” 35

uni'wissen 02-2012 ENG

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