Prof. Isaac Barash

ביולוגיה מול.ואקול.צמחים אמריטוס
Prof. Isaac Barash
Phone: 03-6406251
Fax: 03-6409380
Office: Britannia-Porter, 514


1956-1961  M.Sc.; Plant Protection (with distinction), Hebrew University of Jerusalem,
1961-1965 Ph.D.; Plant Pathology (Biochemistry minor), University of California, Davis, U.S.A.


  American Phytopathological Society (APS Fellow); International Society for Molecular Plant - Microbe Interactions; Israeli Phytopathological Society; International Society for Plant Molecular Biology


Research Grants (since 1992):

1992 Role of Thaxtomins in the pathogenicity of Streptomyces spp. on potato. BARD, The US-Israel Binational Agricultural Research and Development
1992-1995 Role and in situ regulation of growth regulators in tumor production by Erwinia herbicola on Gypsophila paniculata. BARD
1993-1994 Biological control of the greenhouse and sweetpotato whiteflies by entomopathogenic fungi. AID-CDR
1995-1998 Relationship of genes conferring epiphytic fitness and internal multiplication in plants in Erwinia herbicola. BARD
1998-2000 The role of proteins secreted via the hrp gene cluster in pathogenicity of Erwinia herbicola pv. gypsophilae and Erwinia stewartii BARD
1998-2003 The Molecular Basis for Pathogenicity of Clavibacter michiganensis subsp. miciganensis and Erwinia herbicola pathovars gypsophilae and betae. Supported by DFG (Germany) for trilateral cooperative research between Israeli, Palestinian and German Scientist
1997-2001 Advanced detection methods for control of plant bacterial pathogens USAID-CDR (U.S.A.)
1999-2002 Insect pest management with fungi: A mass production technique for farmers USAID-CDR
2001-2004 The roles of hrp-dependent effector proteins and hrp gene regulation as determinants of virulence and host specificity in Erwinia stewartii and E. herbicola. BARD
2001-2004 Molecular basis for transformation of an epiphyte into a plant pathogen as exemplified
by Erwinia herbicola pvs. gypsophilae and betae. Israel Science Foundation


Research Interests

Specific topics explored in my lab:

  • Topic 1; Molecular mechanisms of virulence in phytopathogenic bacteria.
  • Topic 2: The role of quorum sensing in plant-bacteria interactions.


My scientific intersts throughout the years have been aimed at biochemical and molecular aspects of plant-microbe interactions, primarily on bacterial and fungal plant pathogens. During the last decade I have mainly focused on the molecular genetics of virulence in the plant-pathogenic bacterium Pantoea agglomerans (previously known as Erwinia herbicola). This research was carried out in collaboration with Dr. Shulamit Manulis of the Dept. of Plant Pathology, A.R.O., The Volcani Center. P. agglomerans is widespread in nature as an epiphyte on diverse plants as well as a saprophyte in numerous habitats. However, some strains have evolved into gall-forming bacteria on beet, gypsophila and other plants. Thus P. agglomerans pv. gypsophilae incites galls only on gypsophila whereas P. agllomerans pv. betae is pathogenic on beet and gypsophila. Our main efforts are aimed at understanding the molecular determinants, which causes P. agglomerans to “switch” from an epiphyte on numerous plants into gall-forming host-specific pathogen. We discovered that all the pathogenic strains of the gypsophila and beet pathovars respectively harbor a pathogenicity plasmids designated as pPATHPag and pPATHPab. pPATHPag, that was more extensively studied, has a size of approximately 150-kb and appears to accommodate a putative pathogenicity island of more than 70-kb. Many genes associated with virulence including hrp gene cluster, genes encoding type III virulence effectors and genes encoding enzymes for IAA and cytokinin biosynthesis were characterized on the pPATHPag. In addition the pathogenicity plasmids of both pathovars harbor numerous copies of insertion sequences representing five different families. Current research is aimed at answering the following questions: What is the complete inventory of virulence type III effectors delivered through the Hrp system into plant cells by Pag and Pab? What are the genes responsible for host specificity on gypsophila or beet? How the virulence effectors are being regulated? How do they interact with intracellular host plant components to elicit gall formation? What are the plant growth regulators triggered by type III effectors is the share of hrp-independent virulence genes in pathogenicity of Pag or Pab?


Recently we have identified the presence of a quorum sensing (QS) system in P. agglomerans. This bacterium produces C4-homoserine lactone (C4-HL) as the predominant cognate signal. The biosynthetic gene (luxI equivqlent) has already been cloned and the LuxR equivalent and target genes are being search for. The role of QS system in endophytic growth and virulence is currently being investigated.


Recent Publications

Since 1995

Lichter, A., S. Manulis,O. Sagee, Y. Gafni, J. Gray, R. Meilen R. O. Morris, I. Barash. 1995. Production of cytokinins by Erwinia herbicola pv. gypsophilae and isolation of a cytokinin biosynthetic gene. Mol. Plant Microb. Interact 8: 114-121.


Dori, S., Z. Solel, I. Barash. 1995. Cell wall-degrading enzymes produced by Gaeumannomyces graminis var.tritici in vitro and in vivo. Physiological and Molecular Plant Pathology 46: 189-198..


Lichter, A., I. Barash, L. Valinsky S. Manulis. 1995. The genes involved in cytokinin biosynthesis in Erwinia herbicola pv. gypsophilae: characterization and role in gall formation. J. Bacteriol. 177: 4457-4465.


Lichter, A., S. Manulis, L. Valinsky, B. Karniol, I. Barash. 1996. IS1327, a new insertion element in the pathogenicity-associated plasmid of Erwinia herbicola pv. gypsophilae. Mol. Plant. Microb. Interactions 9: 98-104.


Mor, H., G. Gindin, I.S. Ben Zeev, B. Raccah, N.V. Geschtout, N. Ajtkehozhina, I. Barash. 1996. Diversity among isolates of Verticillium lecanii as expressed by DNA polymorphism and virulence towards Bemisia tabaci. Phytoparasitica 24: 111-118.


Gindin,G., I. Barash, B. Raccah,I.S. Ben-Ze'ev, M. Klein. 1996. The potential of some entomopathogenic fungi as biocontrol agents against the onion thrips, Thrips tabaci and the western flower thrips, Frankliniella occidentalis. Folia Entomologica Hungarica 37:37-42.


Nizan, R., I. Barash, L. Valinski, A. Lichter, S. Manulis. 1997. The presence of hrp genes on the pathogenicity-associated plasmid of the tumorigenic bacterium Erwinia herbicola pv. gypsophilae.Mol. Plant Microbe Interactions. Mol. Plant Microb. Interact.10:677-682.


Gafni,Y.,S. Manulis, T. Kunik, A. Lichter, I. Barash, Y. Ophir. 1998. Characterization of auxin synthesis genes of Erwinia herbicola pv. gypsophilae. Isr. J. Plant Sci. 45-279-284.


Valinsky, L.,Manulis, S., Ezra, D., Nizan, R., I. Barash. 1998. A pathogenicity gene isolated from the pPATH of Erwinia herbicola pv. gypsophilae determines host specificity. Mol. Plant Microbe. Interact. (11:753-762).


Manulis, S., A. Haviv-Chesner, M. T. Brandl, S. E. Lindow, I. Barash. 1998. Differential involvement of indole-3-acetic acid biosynthetic pathways in pathogenicity and epiphytic fitness of Erwinia herbicola pv. gypsophilae Mol. Plant Microbe Interact. (11:634-642).


Ezra, D. Barash, I., Valinsky, L. S. Manulis 2000. The dual function in virulence and host-range restriction of a gene isolated from pPATHEhg plasmid of Erwinia herbicola pv. gypsophilae. Mol. Plant-Microbe Interact. 13:683-692.


Gindin, G., Geschtovt N.U., Raccah, B, I. Barash. 2000. Pathogenicity of Verticillium lecanii to different developmental stages of Bemisia tabaci. Phytoparasitica 28:229-239.


Mor, H., Manulis, S., Zuc, M., Nizan, R., Coplin, D. L., I. Barash 2001. Genetic organization of the hrp gene cluster and dspEF operon in Erwinia herbicola pv. gypsophilae., Molec. Plant-Microbe Interact. 14: 431-436..


Guo, M, Manulis, S., Barash, I.., and Lichter, A. (2001). The operon for cytokinin biosynthesis of Erwinia herbicola pv. gypsophilae contains two promoters and is plant induced. Can. J. of Microbiology 47: 1126-1131.


Valinsky, L., Barash, I., Chalupowicz, L., Ezra, D., S. Manulis. 2002. Regulation of HsvG, a host specific virulence gene of Erwinia herbicola pv. gypsophilae. Physiological and Molecular Plant Pathology 60:19-29.


Guo, M., Manulis, S., Mor, H., I. Barash 2002. The presence of diverse IS elements and avrPphD homologue that acts as a virulence factor on the pathogenicity plasmid of Erwin herbcola pv. gypsophila. Molec. Plant-Microbe Interact 15:709-716.


Valinsky, L., Nisan, I., Tu, X., Nisan, G., Rosenshine, I., Hanski, E., Barash, I., S. Manulis 2002. A host-specific virulence protein of Erwinia herbicola pv. gypsophilae is translocated into human epithelial cells by the type III secretion system of enteropathogenic Escherichia coli. Molec. Plant Pathol. 3:97-101.


Nizan-Koren, R., Manulis, S., Mor, H., Iraki, N. M., I. Barash. 2003. The regulatory cascade that activates the Hrp regulon in Erwinia herbicola pv. gypsophilae. Molec. Plant-Microbe Interact 16:249-260.


Manulis, S. and I. Barash. 2003. The molecular basis for transformation of an epiphyte into a gall-forming pathogen as exemplified by Erwinia herbicola pv. gypsophilae, (Stacey, G. and Keen, Plant-Microbe Interactions 6:19-52


Manulis, S. and I. Barash. 2003. Pantoea agglomerans pvs. gypsophilae and betae, a recently-evolved pathogens? Molecular Plant Pathology 20:307-314.


Manulis, S. and I. Barash. 2003. Contribution of virulence determinants from Pseudomonas and other bacteria to hrp-dependent gall formation by Erwinia herbicola pv. gypsophilae. In: Pseudomonas syringae and related pathogens. N. S. Iacobellis (ed.). Kluwer Academic Publishers p373-381.


Ezra, D.,  Barash, I.,  Weinthal, D. M., Gaba, V., S. Manulis. 2004. pthG from Pantoea agglomerans pv. gypsophilae encodes an avirulence effector that determines incompatibility in multiple beet species.  Molec. Plant Pathol. 5:105-114.


Nissan, G., Manulis, S., Weinthal, D.M., Sessa, G. and Barash, I. 2005. Analysis of promoters recognized by HrpL, an alternative sigma factor protein from Pantoea agglomerans pv. gypsophilae. Mol. Plant-Microbe Interact. 18:634-643.


 Barash, I. and S. Manulis. 2005. Hrp-dependent biotrophic mechanism of

          virulence-how it has evolved in tumorigenic bacteria? Phytoparasitica 33:317-324.


Barash I., Panijel, M., Gurel, F., Chalupowicz, L. and  Manulis, S. (2005) Transformation of Pantoea agglomerans into a tumorigenic pathogen. In S. Sorvari  and O.Toldi, eds, Proceedings of the 1st International Conference on Plant-Microbe Interactions: Endophytes and Biocontriol Agents., Lapland, Finland: Saariselka, pp 10-19.


Chalupowicz, L., Barash, I., araSchwartz, M., Aloni, R., Manulis, S. 2006.Comparative  anatomy of gall development on Gypsophila paniculata induced by bacteria with different mechanism of pathogenicity. Planta 224:429-437.


Nissan, G., Manulis, S., Weinthal, D., Mor, H., Sessa, G. and Barash, I. 2006 The type  III effectors HsvG and HsvB of gall-forming Pantoea agglomerans determine host specificityand function as transcriptional activators. Molecular Microbiology 61:1118-1131.


Barash, I. and Manulis-Sasson, S. 2007. Virulence mechanisms and host specificity of gall-forming Pantoea agglomeransTrends in Microbiology 15:538-545.


Weinthal, D.M., Barash, I., Panijel, M., Valinsky, L., Gaba, V. and Manulis-Sasson, S. 2007. Distribution and replication of the pathogenicity plasmid pPATH in diverse populations of the gall-forming Pantoea agglomerans. Applied and Environmental Microbiology 73:7552-7561.


Balaji, V., Jacob-Hirsh, J., Sherf, O., Eichenlaub, R., Iraki, N., Manulis-Sasson, S., Rechavi, G., Barash, I. and Sessa, G. 2008. Tomato transcriptome changes in response to Clavibacter michiganensis subsp. michiganensis reveal a role for ethylene in disease development. Plant Physiology 146:1797-1809.


Kleitman, F., Barash, I., Burger, A., Iraki, N., Falah, F., Sessa, G., Weinthal, D., Chalupowicz, L., Gartemann, K.-H., Eichenlaub, R. and Manulis-Sasson, S. 2008. Characterization of Clavibacter michiganensis subsp. michiganensis population in Israel. European journal of Plant Pathology (121:463-475).


Chalupowicz, L., Manulis-Sasson, S., Itkin, M., Sacher, A., Sessa, G. and Barash I. 2008. Quorum sensing system affects gall development incited by Pantoea agglomerans pv. gypsophilae. Molecular Plant Microbe Interactions 21:1094-1105.


Chalupowicz, L., Barash, I., Panijel, M., Sessa, G. and Manulis-Sasson, S. (2009). Regulatory interactions between quorum-sensing, auxin, cytokinin and the hrp

regulon in relation to gall formation and epiphytic fitness of Pantoea agglomerans pv. gypsophilae. Molecular Plant-Microbe Interactions 22 :649-856.


Barash, I. and Manulis-Sasson, S. (2009). Recent evolution of bacterial pathogens: the gall-forming Pantoea agglomerans case. Annual Review of Phytopathology 47:133-152.


Chalupowicz, L., Cohen-Kandli M., Dror, O., Eichenlaub R., Gartemann K.-H. Sessa G., Barash, I., Manulis-Sasson S. (2010)

Sequential expression of  bacterial virulence and plant defense genes during infection of tomato with Clavibacter michiganensis  subsp. michiganensis. Phytopathology 100:252-261.


Weinthal D. M., Barash, I ., Tzfira, T., Gaba,V., Teper,D., Sessa, G. and Manulis- Sasson, S. (2011).

Characterization of nuclear localization signals in the type III effectors HsvG and HsvB of the gall-forming bacterium Pantoea agglomerans. Microbiology ; 157: 1500 – 1508.


Chalupowicz L, Zellermann E-M, Fluegel O, Dror O, Eichenlaub R, Gartemann, K-H, Savidor, A, Sessa, G., Iraki, N., Barash, I., Manulis-Sasson, S. (2012).

Colonization and movement of GFP-labeled Clavibacter michiganensis subsp. michiganensis during tomato infection. Phytopathology 102:23-31.


Savidor A, Teper D, Gartemann K-H, Eichenlaub R, Chalupowicz  L, Manulis-Sasson  S, Barash I, Tews H, Mayer, K, Giannone, R J, Hettch, R L, Sessa, G. (2012). The Clavibacter michiganensis subsp. michiganensis–tomato interactome reveals the  perception of pathogen by the host and suggests mechanisms of infection. J. Proteome Res. 11:736-50.


Nissan, G., Manulis-Sasson, S., Chalupowicz, L., Teper D., Yeheskel, A., Pasmanik- Chor, M., Sessa, G. and Barash, I. (2012). The type III effector HsvG of the

gall-forming Pantoea agglomerans mediates expression of the host gene HSVGTMolecular Plant-Microbe Interactions 25 :231-240.


Chalupowicz ,L., Weinthal. D., Gaba, V., Sessa, G., Barash, I. and Manulis-|Sasson,      S., 2013. Polar auxin transport is essential for gall formation by Pantoea agglomerans on  gypsophila. Mol. Plant Pathology, 14. 185-190.


Panijel, M., Chalupowicz, L., Sessa, G., Manulis-Sasson, S. and Barash, I. (2013). Global regulatory networks control the Hrp regulon of the gall-forming bacterium

Pantoea agglomerans pv. gypsophilae. Molecular Plant-Microbe Interactions 26 :1031-1043.


Tancos, M.A., Chalupowicz, L., Barash, I., Manulis-Sasson, S. and Smart, C.D.   (2013). Tomato fruit and seed colonization by Clavibacter michiganensis subsp. michiganensis through external and internal routes.

Applied and Environmental Microbiology 79:6948-6957.


Savidor, A., Chalupowicz, L., Teper, D. , Gartemann, K-H., Eichenlaub, R., Manulis-   Sasson, S., Barash, I. and  Sessa, G. (2014). Clavibacter michiganensis subsp. michiganensis transcriptional regulators are required for virulence in tomato. Molecular Plant-Microbe Interactions 27:1035-1047.


Barel, V., Chalupowicz, L., Barash, I., Sharabani, G., Reuven, M., Dror, O., Burdman, S., and Manulis-Sasson, S. 2015. Virulence and in planta movement of Xanthomonashortorum pv. pelargonii are affected by diffusable signal factor (DSF)-dependent quorum sensing system. Molecular Plant Pathology 16 (in press).



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