Doris Wagner

Professor of Biology and Graduate Chair in Biology
103G Carolyn Lynch Laboratory
wagnerdo@sas.upenn.edu
215-898-0483
Plant Biology
Cell and Developmental Biology
Genetics, Epigenetics, Genomics
Computational Biology
Education: 

Ph.D., University of California, Berkeley, 1995

Research Interests: 

transcriptional regulation of developmental transitions; role of chromatin remodeling in inducible gene expression

Developmental transition to reproductive development

My lab is interested in understanding at the molecular level the complex changes that occur when an organism switches developmental programs. Specifically, we investigate the transition from vegetative to reproductive development in the plant model system Arabidopsis thaliana. Onset of flower formation triggers a transition from biomass and resource production in the leaves and branches to allocation of these resources to the next generation in the flowers. Timing of this switch and subsequent flower development are therefore not only vital for plant survival, but also critical for human sustenance and biofuel production. Because of its central importance, many external signals (such as temperlfy mutant phenotypeature and day length) as well as internal cues input into the timing of reproductive development. Upon perception of the required inductive signals cells at the flanks of the stem-cell-pool containing shoot apical meristem give rise to flowers instead of leaves and secondary stems. My lab is interested in identification of all relevant cues and in understanding their integration. We also wish to elucidate how these cues and transcriptional changes direct altered cell fate and developmental programs. Much of our work has focused on the plant specific helix-turn-helix transcription factor LEAFY (LFY), which plays a critical role in these processes.

 

Chromatin remodeling and inducible gene expression

The developmental processes we study and other events in the life of SWI2/SNF2 ATPases act antagonistically to Polycomb repressors during flower patterninga plant that require a switch in survival programs occur in the context of chromatin. Not surprisingly, we have uncovered important roles for proteins that can alter the chromatin state in stimulus-mediated transcriptional reprogramming. One central mechanism for altering the chromatin state is chromatin remodeling, a process that uses the energy derived from ATP hydrolysis to change the interaction between the genomic DNA and the histone octamer in the nucleosome. SWI/SNF ATPases can act in opposition to Polycomb repression, another key mechanism for controlling the activity of genes in euchromatin. My lab is investigating the question how the activity of SWI/SNF chromatin remodelers or Polycomb repressive complexes is regulated to enable them to direct correct cell-type and stimulus-specific chromatin changes.

 

LEAFY binding at the AP1 promoter

Methodologies employed

We use a wide range of approches including  genetics, genomics, computational biology, biochemistry and cell biology.

 

Current and Future Research Projects

1. Integration of known and novel extrinsic and intrinsic cues at the LEAFY locus regulatory regions.

2. Regulation of the switch to flower formation, flower primordium initiation, flower meristem development and flower patterning.

3. Biological roles and regulation of SWI/SNF ATPases.

4. Identification of plant Polycomb response elements, cis regulatory domains that recruit Polycomb Repressive Complexes.

Selected Publications: 

Yamaguchi, N., Winter, C., Wu, M-F., Kanno, Y., Yamaguchi, A., Seo, M., and Wagner, D. (2014) Gibberellin acts positively then negatively to control onset of flower formation in Arabidopsis. Science 344, 638-41.

Efroni, I., Han, S.K., Kim, H.J., Wu, M.F., Sang, Y., Steiner, E., Hong, J.C., Eshed, Y*., and Wagner, D*. (2013). Regulation of leaf maturation by chromatin-mediated modulation of cytokinin responses. Developmental Cell 24, 438-445. * corresponding authors

Yamaguchi, N., Wu, M.-F., Winter, C., Berns, M., Nole-Wilson, S., Yamaguchi, A., Coupland, G., Krizek, B., and Wagner, D. (2013). A Molecular Framework for Auxin-mediated Initiation of Flower Primordia. Developmental Cell 24, 1–12.

Han, S.K., Sang, Y., Rodrigues, A., BIOL425F2010, Wu, M.F., Rodriquez, P.L. and Wagner, D. (2012). The SWI2/SNF2 chromatin remodeling ATPase BRAHMA represses Abscisic Acid Responses in the Absence of the Stress Stimulus in Arabidopsis. Plant Cell 2012;24 4892-4906.

EPIC Planning Committee (2012) (Wagner D. corresponding author). Reading the second Code: Mapping Epigenomes to understand Plant Growth, Development and Adaptation to the Environment. Plant Cell 24 (6) 2257-2261.

Wu, M.F., Sang, Y., Bezhani, S., Yamaguchi, N., Han, S.K., Li, Z., Su, Y., Slewinski, T.L., and Wagner, D. (2012). SWI2/SNF2 chromatin remodeling ATPases overcome polycomb repression and control floral organ identity with the LEAFY and SEPALLATA3 transcription factors. Proceedings of the National Academy of Sciences of the United States of America 109, 3576-3581.

Pastore, J.J., Limpuangthip, A., Yamaguchi, N., Wu, M.F., Sang, Y., Han, S.K., Malaspina, L., Chavdaroff, N., Yamaguchi, A., and Wagner, D. (2011). LATE MERISTEM IDENTITY2 acts together with LEAFY to activate APETALA1. Development 138, 3189-3198.

Winter, C.M., Austin, R.S., Blanvillain-Baufume, S., Reback, M.A., Monniaux, M., Wu, M.F., Sang, Y., Yamaguchi, A., Yamaguchi, N., Parker, J.E., J.E., Parcy, F., Jensen, S.T., Li, H., Wagner, D. (2011). LEAFY Target Genes Reveal Floral Regulatory Logic, cis Motifs, and a Link to Biotic Stimulus Response. Developmental Cell 20, 430-443.

Yamaguchi, A., Wu, M.F., Yang, L., Wu, G., Poethig, R.S., and Wagner, D. (2009). The microRNA-regulated SBP-Box transcription factor SPL3 is a direct upstream activator of LEAFY, FRUITFULL, and APETALA1. Developmental  Cell 17, 268-278.

Courses Taught: 

BIOL 255: Plant Biology

BIOL 483: Epigenetics

BIOL 700: Advanced Topics in Current Biology Research