Universität zu Köln 

Dr. Tina Romeis

Max-Planck-Institut für Pflanzenzüchtungsforschung, Köln
since 10/2004: Institut für Biologie, Freie Universität Berlin
email: romeis@zedat.fu-berlin.de
phone: +49-(0)30 838 53123
website

Running time: 07/2003 – 09/2005

Abstract

Calcium-dependent protein kinases (CDPK) comprise a family of plant serine/threonine kinases that is unique in that the calcium sensor and the effector domain reside within one molecule. Based on the genome sequence, the CDPK family from Arabidopsis thaliana contains 34 members. Although limited in vitro biochemical data is available for some isoforms, little is known about their in vivo function, their in vivo activation and inactivation mechanisms, or their in vivo phosphorylation targets.

However, increasing evidence suggests that CDPKs function as major molecular switches in early plant signal transduction that integrate multiple stress stimuli by sensing the incoming, stimulus-specific calcium signals and converting them into protein phosphorylation signals. Within this proposal we would like to identify and characterise biological function and in vivo regulation mechanisms of CDPK isoforms from Arabidopsis thaliana that are involved in early biotic and abiotic stress signalling.

We have recently shown for a tobacco CDPK isoform that membrane localisation as well as phosphorylation and dephosphorylation are key regulatory steps in the regulation of enzymatic activity in vivo. Depending on the incoming stress stimulus the amplitude and duration of CDPK activation is either transient (upon a mild abiotic stress stimulus) or more sustained (upon elicitation, a biotic or pathogen-related stimulus). In vivo activation of the CDPK enzyme requires phosphorylation at several sites catalysed by autophosphorylation and by an upstream kinase.

Objective (1) is to identify CDPK isoforms from Arabidopsis thaliana that participate in early signalling to environmental stress responses. Selected isoforms will be characterised for posttranslational lipid and phosphorylation modifications that are required for biological function. Objective (2) addresses the signalling cascade(s) in which these CDPKs are integrated with the aim to identify enzymes that, in response to external stimulation, catalyse these post-translational CDPK modifications such as an (upstream) protein kinase and/or (inactivating) protein phosphatase.

Publications resulting from the project:

Böhmer, M. and Romeis, T. (2007). A chemical-genetic approach to elucidate protein kinase function in planta. Plant Mol Biol. 65, 817-27.?

Böhmer, M., Kurth, J., Witte, C.-P., and Romeis, T. (2006). Function of plant calcium-dependent protein kinases in the activation of abiotic and pathogen-related stress responses and its potential application in the generation of stress-resistant plants. In: Floriculture, Ornamental and Plant Biotechnology, Global Science Books Vol III, 367-372. (review)

Ludwig, A.A., Saitoh, S., Felix, G., Freymark, G., Miersch, O., Wasternack, C., Boller, T., Jones, J.D.G, and Romeis, T. (2005). Ethylene-mediated cross-talk between calcium-dependent and mitogen-activated protein kinase signalling controls stress responses in plants. Proc. Natl. Acad. Sci. USA 102, 10736-10741.?

Witte, C.P., Noël, L.D., Gielbert, J., Parker, J.E., and Romeis, T. (2004). Rapid one-step protein purification from plant material using the eight-amino acid StrepII epitope. Plant Mol. Biol. 55, 135-147.?

Ludwig, A. A., Romeis, T., and Jones J. D. G. (2004). CDPK-mediated signalling pathways: specificity and cross-talk. J. Exp. Bot. 55, 181-188.??