Regulatory networks of stem cell control in Arabidopsis

Group Leader: Prof. Dr. Jan U. Lohmann 

Ph: +49 (0)7071 - 601 1303

Fx: +49 (0)7071 - 601 1412

Secretary: Huelya Wicher

Ph: +49 (0)7071 - 601 1411

Fx: +49 (0)7071 - 601 1412

Few scientific topics currently attract as much attention as stem cells. While public debate has focused on embryonic stem cells from animals and humans, stem cells are common to all multicellular organisms. In most animals, the only “true” totipotent stem cell is the fertilised egg and its immediate descendants. Many plant cells, in contrast, continue to be totipotent throughout the plant’s life, and plant stem cells are much more easily obtained and analyzed than those of animals.

Plant stem cells reside at the growing points of a plant, namely the root tip and the shoot apex and are embedded into specialised structures called meristems, which provide a local environment that regulates the homeostasis between proliferation and differentiation. After the transition from vegetative to reproductive development of the plant, floral meristems arise from the main shoot apical meristem and then develop into flowers. Stem cell regulation and floral patterning in Arabidopsis are closely linked, since the homeodomain protein WUSCHEL (WUS) regulates stem cell fate in both shoot and floral meristems. In addition, WUS interacts with the flower-specific transcription factor LEAFY (LFY) to activate transcription of the floral homeotic gene AGAMOUS (AG), which is essential for the correct patterning of flowers. WUS and AG in turn form a negative feedback loop in which AG represses WUS to terminate the maintenance of stem cells in flowers, bringing about the determinate character of flowers.

Current research in Jan Lohmann’s group is aimed at deciphering the global regulatory network underlying plant stem cell control, focusing on three major topics:

1. How is stem cell fate initated and maintained in the shoot apical meristem?

2. How are local transcriptional signals integrated with system wide hormonal signals to synchronize stem cell behaviour with the growth status of the entire plant?

3. How is stem cell maintenance terminated to allow differentiation of flowers?

We use a systems biology approach integrating advanced genomic, genetic and molecular approaches with bioinformatics and mathematical modelling.
The goal of these studies is not only to identify new stem-cell regulators and to understand the interactions between them, but to draw a regulatory map based on mathematical models with predictive functions. Comparing the mechanisms of stem cell homeostasis employed by plants and animals should allow for the identification of common as well as divergent features of stem cell control.

The Lohmann lab is currently accepting applications at the postdoctoral level from candidates with a strong background in systems biology, developmental biology or genetics. 

Personnel

Sabine Buechel, Diploma student
Wolfgang Busch, Ph.D. student
Monika Demar, Technician
Joachim Forner, Postdoc
Jan U. Lohmann, Group leader
Annette Maier, Ph.D. student
Andrej Miotk, Diploma student
Sebastian Schultheiß, Ph.D. student
Christoph Schuster, Ph.D. student
Zhong Zhao, Postdoc

Lab picture summer 2007

from top left: Wolfgang, Stig, Jan, Christoph, Sebi; front row: Zoran, Zhong, Silke, Sabine, Annette, Andrej

Collaborators

Dr. Joe Kieber, University of North Carolina, US
Dr. Markus Schmid, MPI for Developmental Biology
Dr. Thomas Schmülling, FU Berlin
Dr. Klaus Harter, ZMBP, Tübingen
Dr. Gunnar Rätsch, FML, Tübingen

Key publications

Requirement of B2-Type Cyclin Dependent Kinases for meristem integrity in Arabidopsis thaliana.
Andersen, S. U., Buechel, S., Zhao, Z., Ljung, K., Novák, O., Busch, W., Schuster, C., and Lohmann, J. U. (2008)
The Plant Cell 20, 88-100

Whole-genome analysis of the SHORT-ROOT developmental pathway in Arabidopsis.
Levesque, M. P., Vernoux, T., Busch, W., Cui, H., Wang, J. Y., Blilou, I., Hassan, H., Nakajima, K.,
Matsumoto, N., Lohmann, J. U., Scheres, B., and Benfey, P. N. (2006)
PLoS Biology 4, 739-752.

WUSCHEL controls meristem function by direct regulation of cytokinin inducible response regulators.
Leibfried, A., To, J.P.C., Busch, W., Stehling, S., Kehle, A., Demar, M., Kieber, J.J., and Lohmann, J.U. (2005)
Nature 438, 1172-1175.

Integration of spatial and temporal information during floral induction in Arabidopsis.
Wigge, P.A., Kim, M.C., Jaeger, K.E., Busch, W., Schmid, M., Lohmann, J.U., and Weigel D. (2005)
Science 309, 1056-1059.

A gene expression map of Arabidopsis thaliana development.
Schmid, M., Davison, T.S., Henz, S.R., Pape, U.J., Demar, M., Vingron, M., Scholkopf, B., Weigel, D., and Lohmann, J.U. (2005)
Nature Genetics 37, 501-506.

Dissection of floral induction pathways using global expression analysis.
Schmid, M., Uhlenhaut, N.H., Godard, F., Demar, M., Bressan, R., Weigel, D., and Lohmann, J.U. (2003)
Development 130, 6001-12.

A molecular link between stem cell regulation and floral patterning in Arabidopsis.
Lohmann, J. U., Hong, R. L., Hobe, M., Busch, M. A., Parcy, F., Simon, R., and Weigel, D. (2001)
Cell 105, 793-803.

Profiling a plant: Expression analysis in Arabidopsis.
Busch, W., and Lohmann, J. U. (2007)
Curr. Opin. Plant Biol. 10, 136-41.

From Tough Nuts to Touch-Me-Nots.
Lohmann, J. U., and Weigel, D. (2004)
Cell 116, 763-767.

Building Beauty: The Genetic Control of Floral Patterning.
Lohmann, J. U., and Weigel, D. (2002)
Developmental Cell 2, 135-142.