The main research interests of the group are focussed on the transcriptional regulation of plant genes induced upon pathogen infection and during certain stages of plant development. Biochemical, molecular and genetic methods are being employed to; a) identify the function of such genes, b) to pinpoint cis-acting elements required for local pathogen-specific expression within the regulatory regions of these genes, c) to pinpoint cis-acting elements conferring root-specific and senescence-specific gene expression and d) to identify the protein factors involved in the regulation of such genes. Current projects involve:
Molecular and genetic characterization of the plant-specific superfamily of zinc-finger type WRKY transcription factors.
WRKY factors are key regulators of distinct plant defense responses and are also involved in certain developmental programs. Several parsley WRKY factors have been isolated and characterized for their transactivator functions. We could show that WRKY factors regulate two subsequent steps of the pathogen-induced early nuclear plant defense response (Fig. 1).
To better understand and to functionally dissect the different signal transduction processes involving WRKY factors,
- Arabidopsis WRKY 'knock-out' lines are being identified via reverse genetics or are being generated by means of dsRNAi technology.
- Stategies involving overexpression of WRKY gene products and the analyses of WRKY promoter reporter lines are being pursued to determine the functions of members of this transcription factor superfamily.
- Approaches to study the in vivo interaction of the different WRKY factors with their putative target genes have been initiated.
- Use of DNA arrays for comparative expression studies of Arabidopsis WRKY 'knock-out' lines, WRKY overexpressor lines and wildtype plants to obtain information regarding putative primary and secondary target genes are in progress.
Additionally, several Physcomitrella patens WRKY genes have been identified. Such studies have revealed a high evolutionary conservation of this transcription factor family within this member of the bryophytes, one of the most conserved group of old primary land plants dating back to as far as 350 million years ago.
- WRKY null-mutants are being generated by targeted gene disruption, a feasible approach in this moss.
All tested WRKY factors to date show stereotypic binding preference to their cognate cis-acting element, the W box (TTGACC/T). This is achieved by means of a conserved 60 amino acid stretch termed the WRKY domain. How specificity to certain promoters is nonetheless accomplished remains unclear. Experiments aimed at addressing this question have been initiated. Such studies will try to determine
- whether sequences flanking the W box or distinct arrangement of such elements play a role
- or whether the interaction of selected WRKY factors with other defined proteins, resulting in discrete higher-order protein-DNA complexes, determine the efficacy of the bound WRKY protein, thereby leading to distinct transcriptional outputs.
Cis-acting DNA elements mediating rapid local pathogen-responsiveness
The functional dissection of several parsley gene promoters have enabled us to delineate several distinct classes of cis-acting elements capable of mediating rapid fungal elicitor-induced gene expression. These elements and combinations hereof are being used to generate synthetic promoter::GUS reporter gene constructs which are being introduced into Arabidopsis plants. Most of the tested elements mediate local and rapid GUS expression in leaves upon bacterial and fungal infection (Fig. 2) but often also respond to other environmental stresses such as wounding. In a number of cases, tissue-specific expression is also observed. From a scientific point of view we want to
- identify cognate factors binding to such elements by means of the yeast one-hybrid method or by DNA ligand binding assays
- perform mutagenesis screens using transgenic lines containing selected elements thereby identifying upstream signaling components (collaboration with Dr. Kombrink).
From the biotechnological point of view, we want to know whether
- such functionally well defined pathogen-responsive cis-acting elements can be used to construct synthetic promoters capable of driving highly local and pathogen-inducible gene expression in planta.
Members of the team
|| (Technical Assistants)
| Janna Brümmer (German DFG funded fellowship)
|| (Post-doctoral Researcher)
| Nicole Kamphaus
|| (Technical Assistant)
| Elke Logemann
|| (Technical Assistant)
| Muhammad Shahid Mukhtar (IMPRS PhD grant)
|| (PhD Researcher)
|Gaelle Rivoray (German DFG funded PhD-Program "Graduiertenkolleg")
|| (PhD Researchers)
| Mario Roccaro (BMBF-funded grant)
|| (Post-Doctoral Researcher)
| Bekir Ülker (funded by industrial partner)
|| (Post-doctoral Researchers)
Turck, F., Zhou, A., and Somssich, I.E. Stimulus-dependent,
promoter-specific binding of transcription factor WRKY1 to its native
promoter and the defense-related gene PcPR1-1 in parsley. Plant Cell
16, 2573-2585, 2004.
Ülker, B. and Somssich, I.E. WRKY transcription factors: from DNA
binding towards biological function. Curr. Opin. Plant Biol. 7:
Hahlbrock, K., Bednarek, P., Ciolkowski, I., Hamberger, B., Heise,
A., Liedgens, H., Logemann, E., Nürnberger, T., Schmelzer, E.,
Somssich, I.E., Tan, J. Non-self recognition, transcriptional
reprogramming, and secondary metabolite accumulation during
plant/pathogen interactions. Proc. Natl. Acad. Sci. USA 100,
Deslandes, L., Olivier, J., Peeters, N., Feng, D.X., Khounlotham, M.,
Boucher, C., Somssich, I., Genin, S., and Marco, Y. Physical
interaction between RRS1-R, a protein conferring resistance to
bacterial wilt, and PopP2, a type III effector targeted to the plant
cell nucleus. Proc. Natl. Acad.
Sci. USA 100, 8024-8029, 2003.
Somssich, I. E. Closing another gap in the plant SAR puzzle. Cell
113, 815-816, 2003.
Kalde, M., Barth, M., Somssich, I. E. and Lippok, B. Members of the
Arabidopsis WRKY group III transcription factors are part of
different plant defense signaling pathways.
Mol. Plant-Microbe Inter.16, 295-305, 2003.
Robatzek, S. and Somssich, I.E. Targets of AtWRKY6 regulation during
plant senescence and pathogen defense.
Genes Dev.16, 1139-1149, 2002.
Cormack, R.S., Eulgem, T., Rushton, P.J., Köchner, P., Hahlbrock, K.,
Somssich, I. E. Leucine zipper containing
WRKY proteins widen the spectrum of immediate early elicitor-induced
WRKY transcription factors in parsley.
Biochim. Biophys. Acta, 1576, 92-100, 2002.
Rushton, P.J., Reinstädler, A., Lipka, V., Lippok, B., and Somssich, I. E.
Synthetic plant promoters containing defined regulatory elements
provide novel insights into pathogen- and wound-induced signaling.
Plant Cell, 14, 749-762, 2002.
S. Robatzek and Imre E. Somssich
A new member of the Arabidopsis WRKY transcription factor family, AtWRKY6,
is associated with both senescence- and defense-related processes.
Plant J. 28, 123-133, 2001.
Kirsch, C., Takamiya-Wik, M., Schmelzer, E., Hahlbrock, K., and Somssich, I.E.
A novel regulatory element involved in rapid activation of parsley ELI7 gene family members by fungal elicitor or pathogen infection.
Mol. Plant Pathol. 1, 243-251, 2000.
Eulgem, T., Rushton, P.J., Robatzek, S. And Somssich, I.E.
The WRKY superfamily of plant transcription factors.
Trends in Plant Science 5, 199-206, 2000.
Logemann, E., Tavernaro, A., Schulz, W., Somssich, I.E. und Hahlbrock, K.
UV light selectively coinduces supply pathways from primary metabolism and flavonoid secondary product formation in parsley.
Proc. Natl. Acad. Sci. USA 97, 1903-1907, 2000.
Eulgem, T., Rushton, P.J., Schmelzer, E., Hahlbrock, K. and Somssich, I.E.
Early nuclear events in plant defense signaling: rapid gene activation by WRKY transcription factors.
EMBO J. 18, 4689-4699, 1999.
Ehlting, J., Büttner, D., Li, Q., Douglas, C.J., Somssich, I.E. and Kombrink, E.
Three 4-coumarate:Coenzyme A ligases (4CL) in Arabidopsis thaliana represent two evolutionary divergent 4CL classes in angiosperm plants.
Plant J. 19: 9-20, 1999.
Rushton, P.J. and Somssich, I.E.
Transcriptional regulation of plant genes responsive to pathogens and elicitors.
In: Plant-Microbe Interactions Vol. 4, (Stacey, G. and Keen, N. eds.), APS Press, pp. 251-274,1999.
Rushton, P.J. and Somssich, I.E.
Transcriptional control of plant genes responsive to pathogens.
Curr. Opin. Plant Biol. 1: 311-315, 1998.
Cormack, R.S., Hahlbrock, K. and Somssich, I.E.
Isolation of putative transcriptional co-activators using a modified two-hybrid system incorporating a GFP reporter gene.
Plant J. 14: 685-692, 1998.
Somssich, I.E. and Hahlbrock, K.
Pathogen defence in plants - a paradigm of biological complexity.
Trends in Plant Science 3: 86-90, 1998.
The role of MAP kinases in plant defense.
Trends in Plant Science 2: 406-408, 1997.
Kirsch, C., Takamiya-Wik, M., Reimold, S., Hahlbrock, K. and Somssich, I.E. Rapid, transient and highly localized induction of plastidial omega-3 fatty acid desaturase mRNA at fungal infection sites in Petroselinum crispum .
Proc. Natl. Acad. Sci. USA 94: 2079-2084, 1997.
Cormack, R.S. and Somssich, I.E.
Dampening of bait proteins in the two-hybrid system.
Anal. Biochem. 248: 184-186, 1997.
Cormack, R.S. and Somssich, I.E.
Cloning of PCR products via the green fluorescent protein.
Technical Tips Online (http://www.elsevier.com/locate/tto) T01107, 1997.
Kombrink E., Somssich I.E.
Pathogenesis-related proteins and plant defense.
In: The Mycota, Vol. V Part A: Plant Relationships (Carroll G. and Tudzynski P. eds.),Springer Verlag, 107-128, 1997.
Cormack, R.S. and Somssich, I.E.
Rapid amplification of genomic ends (RAGE) as a simple method to clone flanking genomic DNA.
GENE 194: 273-276, 1997.
Plesch, G., Störmann, K., Torres, J.T., Walden, R. and Somssich, I.E.
Developmental and auxin-induced expression of the Arabidopsis prha homeobox gene.
Plant J. 12: 635-647, 1997.
Kirsch, C., Hahlbrock, K. and Somssich, I.E.
Rapid and transient induction of a parsley (Petroselinum crispum) microsomal omega-6 fatty acid desaturase mRNA by fungal elicitor.
Plant Physiol. 115: 283-290, 1997.
Logemann, E., Reinold, S., Somssich, I.E. and Hahlbrock, K.
A novel type of pathogen defense-related cinnamyl alcohol dehydrogenase from parsley.
Biol. Chem. 378: 909-913, 1997.
Somssich, I.E., Weißhaar, B.
Expression library screening.
In: Plant Gene Isolation (Foster G.D. and Twell D. eds.), John Wiley & Sons Ltd., pp 157-176, 1996.
Somssich, I.E., Wernert, P., Kiedrowski, S. and Hahlbrock, K.
The Arabidopsis thaliana defense-related protein ELI3 is an aromatic alcohol:NADP+ oxidoreductase.
Proc. Natl. Acad. Sci. USA 93: 14199-14203, 1996.
Rushton, P.J., Torres, J.T., Parniske, M., Wernert, P., Hahlbrock, K. and Somssich, I.E.
Interaction of elicitor-induced DNA-binding proteins with elicitor response elements in the promoters of parsley PR1 genes.
EMBO J. 15: 5690-5700, 1996.
Van Gijsegem F., Somssich I.E., Scheel D.
Activation of defense-related genes in parsley leaves by infection with Erwinia chrysanthemi.
Eur. J. Plant Pathol. 101: 549-559, 1995.
Logemann E., Sheng-Cheng W., Schröder J., Schmelzer, E., Somssich I.E., Hahlbrock K.
Gene activation by UV light, fungal elicitor or fungal infection in Petroselinum crispum is correlated with repression of cell cycle-related genes.
Plant J. 8: 865-876, 1995.
Wanner L.A., Li G., Ware D., Somssich I.E., Davis K.R.
The phenylalanine ammonia-lyase gene family in Arabidopsis thaliana.
Plant Mol. Biol. 27: 327-338, 1995.
Kawalleck, P., Schmelzer, E., Hahlbrock, K. and Somssich, I.E.
Two pathogen-responsive parsley genes encode a tyrosine-rich hydroxyproline-rich glycoprotein (HRGP) and an anionic peroxidase.
Mol. Gen. Genet. 247: 444-452, 1995.
Kombrink, E., Somssich, I.E.
Defense responses of plants to pathogens.
In: Advances in Botanical Research Vol. 21 (Andrews, J.H. and Tommerup, I.C. eds.), Academic Press Limited, pp 1- 34, 1995.
Regulatory elements governing pathogenesis-related (PR) gene expression.
In: Results and Problems in Cell Differentiation. Vol. 20: Plant Promoters and Transcription Factors.(Nover L. and Dennis E. ed.), Springer Verlag, pp 163-179, 1994.
Korfhage U., Trezzini G.F., Meier I., Hahlbrock K. and Somssich I.E.
Plant homeodomain protein involved in transcriptional regulation of a pathogen defense-related gene.
Plant Cell 6: 695-708, 1994.
Assay for gene expression using run-on transcription in isolated nuclei.
In: Plant Molecular Biology Manual 2nd Edition. (Gelvin S.B. and Schilperoort D.P.S. eds.), E1: pp.1-11. Kluwer Academic Publishers, 1994.
Trezzini G.F., Horrichs A., Somssich I.E.
Isolation of putative defense-related genes from Arabidopsis thaliana and expression in fungal elicitor-treated cells.
Plant Mol. Biol. 21: 385-389, 1993.
Kawalleck P., Keller H., Hahlbrock K., Scheel D., Somssich I.E.
A pathogen-responsive gene of parsley encodes tyrosine decarboxylase.
J. Biol. Chem. 268: 2189-2194, 1993.
Kawalleck P., Somssich I.E., Hahlbrock K., Feldbrügge M., Weisshaar B.
Polyubiquitin gene expression and structural properties of the ubi4-2 gene in Petroselinum crispum.
Plant Mol. Biol. 21: 673-684, 1993.
Tover Torres J., Block A., Hahlbrock K. and Somssich I.E.
Influence of bacterial strain genotype on transient expression of plasmid DNA in plant protoplasts.
Plant J. 4: 587-592, 1993.
Kawalleck P., Hahlbrock K., Somssich I.E.
Induction by fungal elicitor of S-Adenosylmethionine synthetase and S-Adenosylhomocysteine hydrolase mRNAs in cultured cells and leaves of Petroselinum crispum.
Proc. Natl. Acad. Sci. USA 89: 4713 - 4717, 1992.
Kiedrowski S., Kawalleck P., Hahlbrock K., Somssich, I.E., Dangl J.L.
Rapid activation of a novel plant defense gene is strictly dependent on the Arabidopsis RPM1 disease resistance locus.
EMBO J. 11: 4677 - 4684, 1992.
Meier I., Hahlbrock K., Somssich I.E.
Elicitor-inducible and constitutive in vivo DNA footprints indicate novel cis-acting elements in the promoter of a parsley gene encoding pathogenesis-related protein 1.
Plant Cell 3: 309-315, 1991.
Van de Löcht U., Meier I., Hahlbrock K., Somssich I.E.
A 125 bp promoter fragment is sufficient for strong elicitor-mediated gene activation in parsley.
EMBO J. 9: 2945-2950, 1990.
Somssich I.E.,Bollmann J.,Hahlbrock K.,Kombrink E.,Schulz W. Differential early activation of defense-related genes in elicitor treated parsley cells.
Plant Mol. Biol. 12: 227-234, 1989.
Somssich I.E.,Schmelzer E.,Kawalleck P.,Hahlbrock K.
Gene structure and in situ transcript localization of pathogenesis-related protein 1 in parsley.
Mol. Gen. Genet. 213: 93-98, 1988.
Somssich I.E.,Schmelzer E.,Bollmann K.,Hahlbrock K.
Rapid activation by fungal elicitor of genes encoding "pathogenesis-related" proteins in cultured parsley cells.
Proc. Natl. Acad. Sci. USA 83: 2427- 2430, 1986.