Martin Luther University Halle-Wittenberg


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Prof. Dr. Ulla Bonas

Institute of Biology, Dept. of Genetics
Martin- Luther- University
Halle- Wittenberg
Prof. Dr. habil. Ulla Bonas
Weinbergweg 10
D- 06120 Halle (Saale)

Phone: +49- 345- 552 6290
Fax: +49- 345- 552 7277


Plant pathogens use sophisticated strategies to infect their host plants. Xanthomonas campestris pv. vesicatoria (Xcv)  is the causal agent of bacterial spot disease in pepper and tomato.  Essential for its pathogenicity is a type III secretion system that  translocates bacterial effector proteins (T3Es) into the plant cell.  Once inside the plant cell the effector proteins interfere with plant  cell signaling and metabolic pathways to the benefit of the pathogen,  which in turn can multiply in the intercellular spaces of the plant  tissue. The effectors contribute to the virulence of the bacterium, e.g.,  by suppression of plant defense responses. Our key objectives are to  identify and characterize novel bacterial virulence factors and to study  the corresponding plant processes in disease and defense. To date,  twenty-five T3Es have been confirmed experimentally, and five more effector candidates will be analyzed. Our long-term  goal is the analysis of interesting T3ES with respect to their  localization in the plant cell and their potential effect on plant  defense responses, gene expression and other aspects that might be  important during infection, e.g., plant protein secretion and plant cell structure.

However,  resistant tomato and pepper lines specifically recognize certain  "injected" bacterial effector proteins that were designated "avirulence"  proteins. For example, the AvrBs3 protein induces a hypersensitive  reaction (HR) in pepper plants carrying the dominant resistance gene Bs3. The HR is a rapid, localized cell death reaction in the infected plant tissue. In susceptible pepper plants, i.e.,  in the absence of recognition, AvrBs3 induces hypertrophy (cell  enlargement), which reflects the virulence function of AvrBs3.  Hypertrophy also occurs in tomato and other solanaceous plants. Using  immunocytology we have shown that AvrBs3 localizes to the plant nucleus.  AvrBs3 acts as a trnascription factor in plant cells. Its activity  depends on a central region of 34-amino acid repeats, and nuclear localization signals and an acidic activation domain in the C-terminus. Using the yeast-two-hybrid system plant proteins interacting with AvrBs3 were isolated, e.g.,  importin α. Furthermore, we identified plant genes specifically induced  by AvrBs3. Our work focuses on the characterization of AvrBs3 function.

Awards: Gottfried Wilhelm Leibniz-Preis 2011

Ulla Bonas received 2011 the Leibniz-prize from the German science  foundation (DFG). The prize recognized the exciting work of her lab on the interaction between the plant pathogenic bacterium Xanthomonas campestris pv. vesicatoria and its host plants pepper and tomato. A major focus over the last 20 years in her laboratory was the effector protein AvrBs3 from Xanthomonas which turned out to be injected into plant cells via the type III secertion system. After import into the plant cell’s nucleus AvrBs3 binds to promoters of target genes thus manipulating plant gene expression. In sensitive plants, the developmental program is altered leading to cell enlargement and pustules on the leaf surface. By contrast, in resistant pepper plants, AvrBs3 activates a suicide gene which results in plant cell death and the arrest of bacterial multiplication. In a series of seminal papers the biochemical function of AvrBs3 has been elucidated. The findings have not only provided new insights into the mechanism of host-pathogen interactions but also opened new avenues for biotechnology.   

Memberships and professional activities

Spokesperson of the SFB 648 “Molecular mechanisms of information processing in plants”

Member of:

  • the German Academy of Sciences (Leopoldina)
  • the Alexander-von-Humboldt-foundation (Herzog, Lynen)
  • the International Society for Molecular Plant-Microbe Interactions
  • the Association for General and Applied Microbiology (VAAM)
  • the American Society for Microbiology (ASM)
  • the German Botanical Society
  • EMBO
Coeditor of "The Plant Cell"
Member of the Editorial Board of "Trends in Microbiology"

CV Prof. Dr. Ulla Bonas

Last publications and patents

  • Publications 2014

Schreiber T, Bonas U. (2014) Repeat 1 of TAL effectors affects target specificity for the base at position zero. Nucleic Acids Res. 42(11):7160-9
Link to abstract on Pubmed   

Abendroth U, Schmidtke C, Bonas U. (2014) Small non-coding RNAs in plant-pathogenic Xanthomonas spp. RNA Biol. 11(5):457-63
Link to abstract on Pubmed   

  • Publications 2013

Schmidtke C, Abendroth U, Brock J, Serrania J, Becker A and Bonas U  (2013) Small RNA sX13: a multifaceted regulator of virulence in the  plant pathogen Xanthomonas. PLoS Pathog 9: e1003626
Link to abstract on Pubmed   

Grau  J, Wolf A, Reschke M, Bonas U, Posch S and Boch J (2013) Computational  Predictions Provide Insights into the Biology of TAL Effector Target  Sites. PLoS Comput Biol 9: e1002962
Link to abstract on Pubmed   

Singer AU, Schulze S, Skarina T, Xu X, Cui H, Eschen-Lippold  L, Egler M, Srikumar T, Raught B, Lee J, Scheel D, Savchenko A, Bonas  U. (2013) A pathogen type III effector with a novel E3 ubiquitin ligase  architecture. PLoS Pathog 9: e1003121
Link to abstract on Pubmed   

  • Publications 2012

Schulze S, Kay S, Büttner D, Egler M, Eschen-Lippold L, Hause G,  Krüger A, Lee J, Müller O, Scheel D, Szczesny R, Thieme F and Bonas U  (2012) Analysis of new type III effectors from Xanthomonas uncovers XopB  and XopS as suppressors of plant immunity. New Phytol. 195: 894 – 911
Link to abstract on Pubmed   

Schmidtke C, Findeiß S, Sharma CM, Kuhfuß J, Hoffmann S, Vogel J, Stadler PF and Bonas U (2012) Genome-wide transcriptome analysis of the plant pathogen Xanthomonas identifies sRNAs with putative virulence functions. Nucleic Acids Res 40: 2020-2031
Link to abstract on Pubmed   

  • Publications 2011

Geißler R, Scholze H, Hahn S, Streubel J, Bonas U, Behrens S E and Boch J (2011) Transcriptional activators of human genes with programmable DNA-specificity. PLoS One 6: e19509
Link to abstract on Pubmed   

  • Publications 2010

Szczesny R, Jordan M, Schramm C, Schulz S, Cogez V, Bonas U and Büttner D (2010) Functional characterization of the Xcs and Xps type II secretion ATPase HrcN from the plant pathogen Xathomonas campestris pv. vesicatoria. New Phytologist 187: 983-1002
Link to abstract on Pubmed   

Szczesny R, Büttner D, Escolar L, Schulze S, Seiferth A and Bonas U (2010) Suppression of the AvrBs1-specific hypersensitive response by the YopJ effector homolog AvrBsT from Xanthomonas depends on a SNF1-related kinase. New Phytologist 187: 1058-1074
Link to abstract on Pubmed   

Findeiß S, Schmidtke C, Stadler PF and Bonas U (2010) A novel family of plasmid-transferred anti-sense ncRNAs. RNA Biology 7: 1-5
Link to abstract on Pubmed   

  • Publications 2009

Boch J, Scholze H, Schornack S, Landgraf A, Hahn S, Kay S, Lahaye T, Nickstadt A, Bonas U (2009) Breaking the code of DNA-binding specificity of TAL-type III effectors. Science 326: 1509-12
Link to abstract on Pubmed   

Römer P, Strauss T, Hahn S, Scholze H, Morbitzer R, Grau J, Bonas U, Lahaye T (2009) Recognition of AvrBs3-Like Proteins is mediated by specific binding to promoters of matching pepper Bs3 Alleles. Plant Physiol 150: 1697-1712
Link to abstract on PubMed   

Kay S, Hahn S, Marois E, Wieduwild R, Bonas U (2009) Detailed analysis of the DNA recognition motifs of the Xanthomonas type III effectors AvrBs3 and AvrBs3Deltarep16. Plant J 59: 859-871
Link to abstract on PubMed   

Gürlebeck D, Jahn S, Gürlebeck N, Szczesny R, Szurek B, Hahn S, Hause G, Bonas U (2009) Visualization of novel virulence activities of the Xanthomonas type III effectors AvrBs1, AvrBs3 and AvrBs4. Mol Plant Pathol 10: 175-188
Link to abstract on PubMed   

  • Publications 2008

Lorenz C, Schulz S, Wolsch T, Rossier-Conway O, Bonas U, Büttner D (2008)
HpaC controls substrate specificity of the Xanthomonas type III secretion system.
PLoS Pathogens 4: e1000094
Link to abstract on PubMed   

Lorenz C, Kirchner O, Egler M, Stuttmann J, Bonas U, Büttner D (2008)
HpaA from Xanthomonas is a regulator of type III secretion. Mol Microbiol 69: 344-360
Link to abstract on PubMed   

  • Other publications

Kay S, Hahn S, Marois E, Hause G, Bonas U (2007).
A bacterial effector acts as a plant transcription factor and induces a cell size regulator. Science 318: 648-651
Link to abstract on Science   
Link to abstract on PubMed   

Römer P, Hahn S, Jordan T, Strauß T, Bonas U, Lahaye T (2007) .
Plant pathogen recognition mediated by promoter activation of the Pepper Bs3 resistance gene. Science 318: 645-648
Link to abstract on Science   
Link to abstract on PubMed   

Van den Ackerveken G, Marois E, Bonas U (1996)
Recognition of the bacterial avirulence protein AvrBs3 occurs inside the host plant cell. Cell 87: 1307-1316
Link to abstract on Pubmed   

Herbers K, Conrads-Strauch J, Bonas U (1992)
Race-specificity  of plant resistance to bacterial spot disease determined by repetitive  motifs in a bacterial avirulence protein. Nature 356: 172-174

  • Patents

Bonas U, Boch J, Schornack S and Lahaye T (2010) Modular DNA-binding domains and methods of use.

Bonas U, Lahaye T and Römer P. (2008) Bs3 resistance gene and methods of use.

Büttner D and Bonas U (2004). Bacterial system for protein transport in eukaryotic cells.