The Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute - in cooperation with the Friedrich-Schiller-University and the Max Planck Institute for Chemical Ecology are offering an international graduate program. The

International Leibniz Research School (ILRS Jena)

gives PhD students the possibility to prepare for their PhD exam in an ambitious program providing excellent research conditions.

We invite applications for a

Tetramer formation of floral homeotic proteins in planta

Our project investigates the molecular interactions of floral homeotic proteins in multimeric complexes in living plant cells. Floral homeotic MADS-domain transcription factors are developmental key regulators that determine the identity of floral organs. According to the floral quartet model they function by formation of tetrameric complexes in a combinatorial way. MADS domain proteins are well known to bind as dimers to DNA, and the floral quartet model predicts that two dimers bound to two separated cis-regulatory DNA-elements contact each other by looping out the intervening DNA. For each of the different floral organs (e.g., sepals, petals, stamens, carpels), a specific complex determining the identity of the respective organ is predicted (1, 2). Even though the floral quartet model is strongly supported by several series of circumstantial evidence, such as genetic and yeast three-hybrid data, direct experimental support is still scarce, and other models of floral homeotic protein action cannot be excluded (3 - 5).

We have recently shown that in vitro the floral homeotic protein SEPALLATA3 (SEP3) of the model plant Arabidopsis binds cooperatively to DNA by DNA looping, thus providing evidence that at least some floral homeotic proteins posses the intrinsic ability to form complexes as predicted by the quartet model (Melzer and Theißen, manuscript submitted). However, the in planta significance of these findings is unclear.

In the frame of this project it is planned to screen for SEP3 mutants that are specifically defective in tetramer formation using an in vivo yeast assay as well as electrophoretic mobility shift assays. It will be tested whether or not these mutant proteins can rescue a sep knockout phenotype when expressed in Arabidopsis. A similar approach has been successfully used to study the effect of cooperative binding of the BICOID protein during Drosophila embryogenesis (6, 7). Ectopic expression as well as expression under control of the native SEP3 promoter will be used to study whether defects in tetramer formation can be compensated by higher protein concentrations. In a second series of experiments it will be tested whether MADS-domain proteins are capable of looping DNA in planta. Chromosome conformation capture (3C) and related methods (8, 9) will be used to study DNA-looping at specific loci known to be controlled by floral homeotic proteins. For comparison, also plants expressing the SEP3 mutant protein that is not capable of tetramer formation will be analysed. This will not only serve as a control experiment but also unravel the molecular consequences of the loss of tetramer formation.

Cited references:

1.            Theißen, G. (2001) Development of floral organ identity: stories from the MADS house. Curr Opin Plant Biol, 4, 75-85.

2.            Theißen, G. and Saedler, H. (2001) Plant biology. Floral quartets. Nature, 409, 469-471.

3.         Jack, T. (2004) Molecular and genetic mechanisms of floral control. Plant Cell, 16, S1-S17.

4.         Jack, T. (2001) Relearning our ABCs: new twists on an old model. Trends Plant Sci, 6, 310-316.

5.         Honma, T. and Goto, K. (2001) Complexes of MADS-box proteins are sufficient to convert leaves into floral organs. Nature, 409, 525-529.

6.            Lebrecht, D., Foehr, M., Smith, E., Lopes, F.J., Vanario-Alonso, C.E., Reinitz, J., Burz, D.S. and Hanes, S.D. (2005) Bicoid cooperative DNA binding is critical for embryonic patterning in Drosophila. Proc Natl Acad Sci U S A, 102, 13176-13181.

7.         Burz, D.S., Rivera-Pomar, R., Jackle, H. and Hanes, S.D. (1998) Cooperative DNA-binding by Bicoid provides a mechanism for threshold-dependent gene activation in the Drosophila embryo. Embo J, 17, 5998-6009.

8.            Dekker, J., Rippe, K., Dekker, M. and Kleckner, N. (2002) Capturing chromosome conformation. Science, 295, 1306-1311.

9.            Simonis, M., Kooren, J. and de Laat, W. (2007) An evaluation of 3C-based methods to capture DNA interactions. Nature Methods, 4, 895-901.

We expect:

- a Master’s degree (or equivalent) in Natural or Life Sciences. Research at ILRS is centred around “Microbial and biomolecular interactions”. Candidates about to earn their degree are welcome to apply.

- high motivation and interest to join one of the research areas of ILRS

- an integrative and cooperative personality

- very good communication skills in English

We offer:

- a top-level research environment

- efficient supervision by a team of two supervisors

- a comprehensive mentoring program (cf. Program of Study)

- courses in novel technologies and soft skills

- a highly communicative atmosphere between the involved institutions

- Jena – the German City of Science 2008: a young and lively city with dynamic business activities, successful scientific centres of innovation and a vibrant cultural scene around the famous Friedrich Schiller University

The positions are available starting in January 2009 and for three years. Salary will be according to TV-L (salary agreement for public service employees).

HKI is an equal opportunity employer.

Further information:

Prof. Dr. Günter Theißen,                                 guenter.theissen@uni-jena.de

Dr. Dorit Schmidt, ILRS Coordinator,            ilrs@hki-jena.de

For the first step of the application procedure please acquaint yourself with the scientific projects offered on our website

www.ilrs.hki-jena.de

and thoroughly fill in the “Statement of Interest” form downloadable from this site. The application procedure is handled online exclusively via the ILRS website. Applications can only be considered upon receipt of the completed “Statement of Interest” form submitted to

ilrs@hki-jena.de .

Deadline for submission of the ‘Statement of Interest’: October 30^th, 2008.

Successful applicants will be invited to attend a recruitment meeting in December 2008.

To apply:

For the first step of the application procedure please acquaint yourself with the scientific projects offered on our website

www.ilrs.hki-jena.de
and thoroughly fill in the “Statement of Interest” form downloadable from this site. The application procedure is handled online exclusively via the ILRS website. Applications can only be considered upon receipt of the completed “Statement of Interest” form submitted to
ilrs@hki-jena.de .

Deadline for submission of the ‘Statement of Interest’: October 30^th, 2008.

Successful applicants will be invited to attend a recruitment meeting in December 2008.

The Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute - in cooperation with the Friedrich-Schiller-University and the Max Planck Institute for Chemical Ecology are offering an international graduate program. The

International Leibniz Research School (ILRS Jena)

gives PhD students the possibility to prepare for their PhD exam in an ambitious program providing excellent research conditions.