Laser-Scanning Mikroskop mit konfokaler Optik
Zusammenfassung der Projektergebnisse
Environmental control of plant stem cell behavior: As sessile organisms, plants are exposed to extreme variations in environmental conditions over the course of their lives. Since plants grow and initiate new organs continuously, they have to modulate the underlying developmental program accordingly to cope with this challenge. At the heart of this extraordinary developmental plasticity are pluripotent stem cells, which are maintained during the entire life-cycle of the plant and that are embedded within dynamic stem cell niches. Using the funded instrument, we studied cell behavior in the apical stem cell niche of the reference plant Arabidopsis by multi-spectral live imaging. We have developed a pipeline for tracing all cells in the stem cell system, quantifying individual cell populations and their location, as well as recording their division rate. First results demonstrate that light and energy metabolites are required to activate dormant stem cells after germination and that temperature has a profound effect on stem cell fate and the cellular layout of the stem cell system. Mechanisms of WUSCHEL protein function: Induction and maintenance of stem cell fate by non-cell autonomous signals is a feature shared by many organisms and may depend on secreted factors, direct cell-cell contact, matrix interactions, or a combination of these mechanisms. While many basic cellular processes are well conserved between animals and plants, cell-to-cell signaling is one function where substantial diversity has arisen between the two kingdoms of life. One of the most striking differences is the presence of cytoplasmic bridges, called plasmodesmata, which facilitate the exchange of molecules between neighboring plant cells and provide a unique route for cell-cell communication in the plant lineage. Using the funded confocal microscope, we were able to show that the stem cell inducing transcription factor WUSCHEL (WUS), expressed in cells of the niche, moves to the stem cells via plasmodesmata in a highly regulated fashion and that this movement is required for WUS function and thus stem cell activity in Arabidopsis thaliana. We showed that cell context independent mobility is encoded in the WUS protein sequence and mediated by multiple domains. Finally, we demonstrated that parts of the protein that restrict movement are required for WUS homodimerization, suggesting that formation of WUS dimers might contribute to the regulation apical stem cell activity. Hormonal and transcriptional control of shoot meristem activity: How cell behaviour downstream of the WUSCHEL transcription factor is orchestrated with the developmental state of the entire plant and how the functional compartments of the stem cell system communicate is still poorly understood. Using the funded microscope, we demonstrated that the bHLH transcription factor HECATE1 (HEC1) regulates stem cell proliferation in a cell-type specific manner, and is tightly embedded into the SAM regulatory network. We delineated a universal feedback system controlling meristem activity in which phytohormone response factors can act as mobile cell-to-cell signals, and show that genes with functions in metabolism and hormone signalling respond to essential regulators of plant stem cells. Phytohormones also play important roles during flower and fruit patterning, morphogenesis and growth, and there is emerging evidence for a crosstalk between different classes of plant hormones throughout these processes. Using the funded microscope, we showed that HEC1, HEC2 and HEC3, which have previously been identified as essential components of transmitting tract formation, affect both auxin and cytokinin responses during reproductive tissue development. We found that HEC1 interacts with SPATULA (SPT) to control carpel fusion and that both transcription factors restrict sensitivity to cytokinin in the gynoecium. Conversely, HEC1 is tightly integrated into the auxin-signalling network at the levels of biosynthesis, transport and transcriptional response.
Projektbezogene Publikationen (Auswahl)
- A mechanistic framework of noncell autonomous stem cell induction in Arabidopsis. PNAS 111, 14619-24
Daum, G., Medzihradszky, A., Suzaki, T., and Lohmann J.U.
(Siehe online unter https://doi.org/10.1073/pnas.1406446111) - A regulatory framework for shoot stem cell control integrating metabolic, transcriptional, and phytohormone signals. Developmental Cell 28, 438-49
Schuster, C., Gaillochet, C., Medzihradszky, A., Busch, W., Daum, G., Krebs, M., Kehle, A., and Lohmann, J.U.
(Siehe online unter https://doi.org/10.1016/j.devcel.2014.01.013) - Arabidopsis HECATE genes function in phytohormone control during gynoecium and fruit development. Development 142, 3343-50
Schuster, C., Gaillochet, C., and Lohmann, J.U.
(Siehe online unter https://doi.org/10.1242/dev.120444) - GreenGate – a novel versatile, and efficient cloning system for plant transgenesis. PLOS One 8, e83043
Lampropoulos, A., Sutikovic, Z., Wenzl, C., Maegele, I., Lohmann, J.U., and Forner, J.
(Siehe online unter https://doi.org/10.1371/journal.pone.0083043) - Integration of light and metabolic signals for stem cell activation at the shoot apical meristem. eLife 5, e17023
Pfeiffer, A., Janocha, D., Dong, Y., Medzihradszky, A., Schöne, S., Daum, G., Suzaki, T., Forner, J., Langenecker, T., Rempel, E., Schmid, M., Wirtz, M., Hell, R., and Lohmann J.U.
(Siehe online unter https://doi.org/10.7554/eLife.17023) - Job sharing in the endomembrane system: vacuolar acidification requires the combined activity of V-ATPase and V-PPase. Plant Cell 27, 3383-96
Kriegel, A., Andrés, Z., Medzihradszky, A., Krüger, F., Scholl, S., Delang, S., Patir-Nebioglu, M. G., Gute, G., Yang, H., Murphy, A.S., Peer, W. A., Pfeiffer, A., Krebs, W., Lohmann, J. U., and Schumacher, K.
(Siehe online unter https://doi.org/10.1105/tpc.15.00733) - Live Imaging of Arabidopsis Development. Methods in Molecular Biology 1062, 539-50
von Wangenheim, D., Daum, G., Lohmann, J. U., Stelzer, E. K., and Maizel, A.
(Siehe online unter https://doi.org/10.1007/978-1-62703-580-4_28) - Regulation of plant stem cell quiescence by a novel Brassinosteroid signaling module. Developmental Cell 30, 36-47
Vilarrasa-Blasi, J., González-García, M., Frigola, D., Fàbregas, N., Alexiou, K., López-Bigas, N., Rivas, S., Jauneau, A., Lohmann, J. U., Benfey, P. N., Ibañes, M., and Caño-Delgado, A.
(Siehe online unter https://doi.org/10.1016/j.devcel.2014.05.020)
