Unlike most animals, plants can grow and form new organs throughout their life, which in the case of some long-lived trees can last for more than a thousand years. The requisite cells are supplied by pluripotent stem cells in the proliferative centers plants, the meristems. In addition to their longevity, plant growth and thus stem cell activity must adjust to environmental signals, such as season, light, water and nutrient supply. How active stem cells can be maintained for such a long time and how they sense and adapt to environmental conditions is a central question for both, stem cell biology and agriculture.
Our group previously has shown that the stem cells of the shoot meristem are regulated by a local, negative feedback loop between the transcription factor WUSCHEL (WUS) and the signaling peptide CLAVATA3 (Mayer at al, Cell 1998; Schoof et al, Cell 2000). We also found that the root meristem functions in a similar way, expressing the WUS homolog WOX5 (Sarkar et al., Nature 2007). WOX5 is required to maintain pluripotency of the stem cells forming the gravity sensing columella, and can also reprogram differentiated columella cells to induced pluripotent stem cells (iPS). The WOX5 protein changes the chromatin of the stem cells by recruiting a histone modifying enzyme to the DNA of its target genes, and as consequence, the chromatin becomes compacted and the genes silenced (Pi et al., Developmental Cell, 2015). The columella stem cells are a prefect model to study stem cell regulation, because it consists only of three cell types: the niche cells, called the quiescent center, that signal the stem cells to remain pluripotent, the dividing stem cells, and their differentiated daughter cells, the gravity sensing columella cells. The root stem cells additionally must adapt to a number of abiotic and biotic environmental challenges including drought, flooding, nutrient shortage, soil contamination but also bacterial and fungal infections. Understanding how stem cells cope with these conditions to maintain root growth is not only of highest importance to stem cell biology, but also for agriculture, especially considering the effects of global climate change.
To understand how the genetic and epigenetic networks that regulate stem cells are affected by and respond to environmental signals in order to cope with adverse conditions.
In addition to standard genetic and molecular tools, the projects utilize a novel microfluidic technology developed together with our engineering partners. This set up simulates environmental changes and enables simultaneous 3-dimensional live imaging of cells and of fluorescent reporter proteins. Transcriptomic, epigenetic, and live imaging data will be combined to create models of how the regulatory networks of stem cells cope with changing environmental conditions. We will test the role of specific genes by creating CRISPR/Cas9 induced mutants and comparing how environmental adaptation changed compared to the wild type. Results will finally be used to formulate breeding concepts with our collaborators at the Shandong Agricultural University in Tai’an (China) to improve root growth under adverse conditions, such as drought or compromised soil.
The language of communication is in English; knowledge of German is not required. For further information, also on our publications, please visit our homepage (http://www.biologie.uni-freiburg.de/LauxLab). The University of Freiburg, with a strong and international scientific community, is routinely among the best German Universities in international rankings, and advanced facilities for systems biology, protein analysis, and imaging are available. The city of Freiburg is located in the Black Forest, next to France, Switzerland and the Alps.
To apply, please send your CV, including your research experiences and your future interests to Thomas Laux (firstname.lastname@example.org).
The PhD position covers the entire length of the PhD with a competitive salary and additional social benefits.