apl. Prof. Dr. Daniela Büttner
Daniela Büttner
Institute of Biology, Dept. of Genetics
Martin- Luther- University
Halle- Wittenberg
apl. Prof. Dr. Daniela Büttner
Weinbergweg 10
D- 06120 Halle (Saale)
Germany
Phone: +49- 345- 552 6293
Fax: +49- 345- 552 7151
E-mail: daniela.buettner@genetik.uni-halle.de
This site contents:
Research: Protein secretion in the plant-pathogenic bacterium Xanthomonas
Gram-negative pathogenic bacteria utilize different types of protein secretion systems to transport virulence factors into the extracellular milieu or directly into the host cell. We study type II secretion (T2S) and type III secretion (T3S) systems in the plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria, which is the causal agent of bacterial spot disease in pepper and tomato plants. X. campestris pv. vesicatoria utilizes a T3S system to translocate a cocktail of approximately 30 effector proteins into the plant cell where they interfere with cellular processes such as defense responses to the benefit of the pathogen (Büttner & Bonas, 2010). The T3S system is an essential bacterial pathogenicity factor, not only in X. campestris pv. vesicatoria but also in the majority of Gram-negative plant- and animal-pathogenic bacteria (Büttner, 2012). The core architecture of the T3S system is presumably conserved in different bacterial species, however, the cargo proteins differ and presumably reflect bacterial adaptations to specific host organisms. In addition to the T3S system, the interaction of X. campestris pv. vesicatoria with its host plants depends on a T2S system, which secretes degradative enzymes such as xylanases and proteases and likely contributes to the degradation of the plant cell wall, which is a major obstacle for invading pathogens.
1. Analysis of components of the T3S system from Xanthomonas
Components of the T3S system from X. campestris pv. vesicatoria are encoded by the chromosomal hrp (hypersensitive response and pathogenicity) gene cluster, which contains more than 20 genes. Eleven genes are conserved among plant-pathogenic bacteria and were therefore designated hrc for hrp conserved. They presumably encode the core components of the secretion apparatus, which consists of ring structures in the outer and inner membrane. The inner membrane ring is associated with the export apparatus, the cytoplasmic ATPase complex and a predicted cytoplasmic ring (Büttner, 2012). The outer membrane ring is connected to an extracellular pilus, which presumably serves as a transport channel for secreted proteins to the host-pathogen interface. Translocation of effector proteins depends on the T3S translocon, which inserts into the host plasma membrane (Büttner et al., 2002; Büttner, 2012).
We have previously shown that type III secretion depends on the ATPase HrcN (Lorenz & Büttner, 2009), the predicted cytoplasmic ring component HrcQ (Lorenz et al., 2012) and the predicted inner rod proteins HrpB1 and HrpB2 (Hartmann et al., 2012; Hausner et al., 2013). The inner rod is a periplasmic substructure of the T3S system, which is presumably required for pilus assembly (Büttner, 2012). Substrate recognition at the cytoplasmic side of the T3S system is probably controlled by HrcU and HrcV, two components of the export apparatus that possess large cytoplasmic domains and interact with secreted proteins (Hartmann & Büttner, 2013; Hausner & Buettner, 2014; Lorenz & Büttner, 2011).
2. Control of T3S in Xanthomonas
T3S substrate specificity is controlled by the T3S substrate specificity switch (T3S4) protein HpaC, which promotes secretion of late substrates after the assembly of the T3S system (Büttner et al., 2006; Lorenz et al., 2008b). The HpaC-mediated switch in T3S substrate specificity presumably depends on the interaction of HpaC with the cytoplasmic domain of the IM protein HrcU. Experimental evidence suggests that HpaC induces a conformational change in the cytoplasmic domain of HrcU and activates effector protein secretion after pilus assembly (Hausner & Buettner, 2014; Lorenz et al., 2008b; Lorenz & Büttner, 2011; Schulz & Büttner, 2011).
In addition to HpaC, T3S in X. campestris pv. vesicatoria depends on the control protein HpaB, which acts as a general T3S chaperone and binds to effector proteins. HpaB presumably targets effector proteins to the cytoplasmic ATPase of the T3S system, which dissociates HpaB-effector complexes and thus might facilitate the entry of effector proteins into the inner channel of the T3S system (Büttner et al., 2004; Lorenz & Büttner, 2009). The activity of HpaB is regulated by the effector protein HpaA, which binds to HpaB and is required for the efficient secretion of pilus and translocon proteins during the assembly of the T3S system (Lorenz et al., 2008a).
3. Identification of type II-secreted virulence factors from Xanthomonas
Given the coregulation of T2S and T3S genes, it was postulated that the local degradation of the plant cell wall by T2S substrates facilitates the expansion of the extracellular pilus of the T3S system. X. campestris pv. vesicatoria contains two T2S systems, which are designated Xcs- and Xps-T2S system. The Xps-T2S system contributes to virulence and T3S-mediated effector protein delivery (Szczesny et al., 2010). Among the substrates of the Xps-T2S system from X. campestris pv. vesicatoria are proteases and the xylanase XCV0965, which contributes to virulence and is required for the extracellular xylanase activity of Xcv (Szczesny et al., 2010). Notably, several tested candidate proteins with homology to type II-secreted extracellular enzymes from other pathogens are secreted T2S-independently in X. campestris pv. vesicatoria (Szczesny et al., 2010). This finding contradicts the anticipated conservation of T2S substrates repertoires and suggests pathogen-specific differences in T2S substrate specificities that might reflect bacterial adaptations to certain environments or host plants.
References
Büttner, D., Nennstiel, D., Klüsener, B. & Bonas, U. (2002). Functional analysis of HrpF, a putative type III translocon protein from Xanthomonas campestris pv. vesicatoria. J Bacteriol 184, 2389-2398.
Büttner, D., Gürlebeck, D., Noel, L. D. & Bonas, U. (2004). HpaB from Xanthomonas campestris pv. vesicatoria acts as an exit control protein in type III-dependent protein secretion. Mol Microbiol 54, 755-768.
Büttner, D., Lorenz, C., Weber, E. & Bonas, U. (2006). Targeting of two effector protein classes to the type III secretion system by a HpaC- and HpaB-dependent protein complex from Xanthomonas campestris pv. vesicatoria. Mol Microbiol 59, 513-527.
Büttner, D. & Bonas, U. (2010). Regulation and secretion of Xanthomonas virulence factors. FEMS Microbiol Rev 34, 107-133.
Büttner, D. (2012). Protein export according to schedule – architecture, assembly and regulation of type III secretion systems from plant and animal pathogenic bacteria. Microbiol Mol Biol Rev 76, 262-310.
Hartmann, N., Schulz, S., Lorenz, C., Fraas, S., Hause, G. & Büttner, D. (2012). Characterization of HrpB2 from Xanthomonas campestris pv. vesicatoria identifies protein regions that are essential for type III secretion pilus formation. Microbiol 158, 1334-1349.
Hartmann, N. & Büttner, D. (2013). The inner membrane protein HrcV from Xanthomonas is involved in substrate docking during type III secretion. Mol Plant Microbe Interact 26, 1176-1189.
Hausner, J., Hartmann, N., Lorenz, C. & Büttner, D. (2013). The periplasmic HrpB1 protein from Xanthomonas spp. binds to peptidoglycan and to components of the type III secretion system. Appl Environ Microbiol 79, 6312-6324.
Hausner, J. & Buettner, D. (2014). The YscU/FlhB homolog HrcU from Xanthomonas controls type III secretion and translocation of early and late substrates. Microbiol 160, 576-588.
Lorenz, C., Kirchner, O., Egler, M., Stuttmann, J., Bonas, U. & Büttner, D. (2008a). HpaA from Xanthomonas is a regulator of type III secretion. Mol Microbiol 69, 344-360.
Lorenz, C., Schulz, S., Wolsch, T., Rossier, O., Bonas, U. & Büttner, D. (2008b). HpaC controls substrate specificity of the Xanthomonas type III secretion system. PLoS Pathog 4, e1000094.
Lorenz, C. & Büttner, D. (2009). Functional characterization of the type III secretion ATPase HrcN from the plant pathogen Xanthomonas campestris pv. vesicatoria. J Bacteriol 191, 1414-1428.
Lorenz, C. & Büttner, D. (2011). Secretion of early and late substrates of the type III secretion system from Xanthomonas is controlled by HpaC and the C-terminal domain of HrcU. Mol Microbiol 79, 447-467.
Lorenz, C., Hausner, J. & Büttner, D. (2012). HrcQ provides a docking site for early and late type III secretion substrates from Xanthomonas. PLoS ONE 7, e51063.
Schulz, S. & Büttner, D. (2011). Functional characterization of the type III secretion substrate specificity switch protein HpaC from Xanthomonas. Infect Immun 79, 2998-3011.
Szczesny, R., Jordan, M., Schramm, C., Schulz, S., Cogez, V., Bonas, U. & Büttner, D. (2010). Functional characterization of the Xps and Xcs type II secretion systems from the plant pathogenic bacterium Xanthomonas campestris pv. vesicatoria. New Phytol 187, 983-1002.
Last publications and patents
Publications 2017
Hausner J, Hartmann N, Jordan M, Büttner, D (2017) The predicted lytic transglycosylase HpaH from Xanthomonas campestris pv. vesicatoria associates with the type III secretion system and promotes effector protein translocation.Infect Immunol, 85:e00788
Publications 2016
Scheibner F, Schulz S, Hausner J, Marillonnet S, Büttner D (2016) Type III-dependent translocation of HrpB2 by a non-pathogenic hpaABC mutant of the plant-pathogenic bacteriumXanthomonas. Appl Env Microbiol, 82: 3331-3347.
Publications 2015
Solé M, Scheibner F, Hoffmeister AK, Hartmann N, Hause G, Rother A, Jordan M, Lautier M, Arlat M, Büttner D (2015) Xanthomonas campestrispv. vesicatoria secretes proteases and xylanases via the Xps type II secretion system and outer membrane vesicles. J Bacteriol 197: 2879-2893.
Publications 2014
Hausner J, Büttner D. (2014) The YscU/FlhB homologue HrcU from Xanthomonas controls type III secretion and translocation of early and late substrates. Microbiology 160(Pt 3):576-88.
Publications 2013
Hausner J, Hartmann N, Lorenz C, Büttner D (2013) The periplasmic HrpB1 protein from Xanthomonas binds to peptidoglycan and to components of the type III secretion system. Appl Env Microbiol 79(20):6312-24.
Hartmann N, Büttner D (2013) The inner membrane protein HrcV from Xanthomonas is involved in substrate docking during type III secretion. Mol Plant-Microbe Interact 26: 1176-1189.
Dejean G, Blanvillain-Baufume S, Boulanger A, Darrasse A, de Bernonville TD, Girard AL, Carrere S, Jamet S, Zischek C, Lautier M, Solé M, Büttner D, Jacques MA, Lauber E, Arlat M (2013) The xylan utilization system of the plant pathogen Xanthomonas campestris pv campestris controls epiphytic life and reveals common features with oligotrophic bacteria and animal gut symbionts. New Phytol198:899-915.
Publications 2012
Lorenz, C., Hausner, J., Büttner, D. (2012) HrcQ provides a docking site for early and late type III secretion substrates from Xanthomonas.“ PLoS One 7: e51063.
Schulze, S., Kay, S. Büttner, D., Egler, M., Eschen-Lippold, L., Hause, G., Krüger, A., Lee, J., Müller, O., Scheel, D., Szczesny, R., Thieme, R., 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.
Kirchberg J., Büttner D., Thiemer B., Sawers G. (2012) Aconitase B is required for optimal growth of Xanthomonas campestris pv. vesicatoria in pepper plants. PLoS One 7, e34941.
Publications 2011
Hartmann N., Schulz S., Lorenz C., Fraas S., Hause G., Büttner D. (2012) Characterization of HrpB2 from Xanthomonas campestris pv. vesicatoria identifies protein regions that are essential for type III secretion pilus formation. Microbiol 158, 1334-1349.
Schulz S, Büttner D (2011) Functional characterization of the type III secretion substrate specificity switch protein HpaC from Xanthomonas. Infect Imm 79: 2998-3011.
Lorenz C. and Büttner D. (2011) Secretion of early and late substrates of the type III secretion system from Xanthomonas is controlled by HpaC and the C-terminal domain of HrcU. Mol Microbiol, 79: 447-467.
Publications 2010
Büttner D, Bonas U (2010) “Regulation and secretion of Xanthomonas virulence factors. FEMS Microbiol Rev, 34: 107-133.
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
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
Publications 2009
Lorenz C, Büttner D (2009) „Functional characterization of the type III secretion ATPase HrcN from the plant pathogen Xanthomonas campestris pv. vesicatoria.“ J Bacteriol 191, 1414-1428.
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 Path, 4: e1000094.
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.
Patents
Büttner, D. und Bonas, U. (2005)
Bacterial system for protein transport in eukaryotic cells.