Investigating the modes of action of the plant steroid hormones brassinosteroids

Plant growth and development is regulated by the coordinated interaction of a multitude of plant hormones that act to integrate endogenous developmental programmes with stimuli perceived from the environment. One class of plant hormones are the brassinosteroids (BRs), steroid hormones that are essential for cell division, differentiation and elongation. The BRs act as master regulators of developmental programs including germination, shoot and root growth, flowering, fruit development and senescence. Moreover BRs are thought to confer abiotic and biotic stress resistance.

We aim to elucidate the function of BRs in plants and are in particular also interested in the molecular mechanisms, which regulate levels of bioactive BRs and thereby confer their effects. In this context we are characterizing proteins that regulate BR production and analyze the significance of catabolic inactivation in the regulation of BR homeostasis. Moreover we try to understand which internal and external stimuli impact on BR levels (crosstalk with other signaling pathways) and how alterations in BR concentrations impact on plant growth and development.

We use tools of molecular biology, biochemistry and genetics in model organisms such as yeast and Arabidopsis thaliana to answer basic research questions in a timely fashion. Moreover, we are involved in and committed to translational and applied research and work with plant species of relevance for horticulture to investigate BR action in crops.

Representative publications:

Eremina, M., Unterholzner, S., Rozhon, W., Kugler, K.G., Castellanos, M., Ratnajaka, A., Khan, M., May, S., Mayer, K.M. & Poppenberger, B.* (2016) Brassinosteroids contribute to the control of basal and acquired freezing tolerance in plants. 
Proc Nat Acad Sci USA. 113(40): E5982-E5991

Unterholzner, S., Rozhon, W., Papacek, M., Lange, T., Kugler, K.G., Mayer, K.M., Sieberer, T. and Poppenberger, B.* (2015) Brassinosteroids Are Master Regulators of Gibberellin Biosynthesis in Arabidopsis. 
Plant Cell. 27(8): 2261-2272

Khan, M., Rozhon, W., Unterholzner, S.J., Chen, T., Eremina, M., Wurzinger, B., Bachmair, A., Teige, M., Sieberer, T., Isono, E. and Poppenberger, B.* (2014) Interplay between phosphorylation and SUMOylation events determines CESTA protein fate in brassinosteroid signalling.
Nature Communic. 5: 4687

Khan, M., Rozhon, W., Bigeard, J., Pflieger, D., Husar, S., Pitzschke, A., Jonak, C., Hirt, H. and Poppenberger B.* (2013) Brassinosteroid-regulated GSK3/shaggy-like kinases phosphorylate MAP kinase kinases, which control stomata development in Arabidopsis thaliana.
J. Biol. Chem. 288(11): 7519-7527

Poppenberger, B.*, Rozhon, W., Khan, M., Husar, S., Adam, G., Luschnig, C., Fujioka, S. and Sieberer, T. (2011) CESTA a positive regulator of brassinosteroid biosynthesis.
EMBO J. 30(6): 1149-1161

Poppenberger, B., Fujioka, S., Sueno, K., George, G.L., Vaistij, F.E., Seto, H., Hiranuma, S., Takastuto, S., Adam, G., Yoshida, S. and Bowles, D. (2005) The UGT73C5 of Arabidopsis thaliana glucosylates brassinosteroids. 
Proc. Nat. Acad. Sci. USA. 102 (42): 15253-15258