Principal investigator:

Prof. Dr. Jan Lohmann

Universität Heidelberg

Centre for Organismal Studies

Stammzellbiologie

Im Neuenheimer Feld 230, 69120 Heidelberg

Tel 06221 – 54 6269

Fax 06221 – 54 6424

jan.lohmannspam prevention@cos.uni-heidelberg.de

Summary:

During development and growth, dynamic signals need to be translated into spatially precise and temporally stable gene expression states, which define cell fate. In the context of the apical plant stem cell system, local accumulation of the small, highly mobile phytohormone auxin triggers organ initiation. At the same time, stem cells are continuously maintained despite abundant auxin signalling input. During the first funding period, we have found that spatial specificity in the auxin response is achieved by direct, pathway-wide transcriptional gating by the WUSCHEL transcription factor in stem cells. Conversely, we discovered that auxin is also required for initiation or maintenance of stem cells in the shoot apex. Thus, our results so far identified a complex regulatory system that confers robustness against fluctuations of a mobile and highly potent developmental signal and thus prevents termination of an essential stem cell pool. In the second funding period, we will now use these results as a stepping stone to investigate the mechanisms by which auxin signaling contributes to stem cell fate, how spatial specificity is encoded in the autocatalytic properties of WUS expression and how a single transcription factor is able to orchestrate a complex hormone response code by rheostatically acting on a large set of transcriptional regulators. We will closely collaborate with subproject B08 led by Thomas Greb to unravel the mechanisms responsible for the spatio-temporal specificity in the fundamental cell-fate decision between proliferation and differentiation in the stem cell systems of shoot apex and cambium.