Research Interests
My research interests are concerned with
understanding how bacterial pathogens cause disease in plants and how their
strategies differ from the strategies employed by bacterial pathogens of
animals. Research in my laboratory primarily is focused on understanding a
specialized protein secretion apparatus, called the type III secretion system,
present in gram-negative bacterial pathogens of plants and animals. Type III
systems secrete multiple virulence proteins, some of which are transferred
directly into eukaryotic cells in a contact dependent manner. Acquisition of a
type III secretion system appears to be a key adaptation that allowed many
gram-negative bacteria to become pathogens – mutants with a disabled type III
system are essentially nonpathogenic. My research group studies the type III
secretion system present in the bacterial plant pathogen, Pseudomonas
syringae. P. syringae is a leaf spotting pathogen whose various strains
display host specificity: Different strains are only capable of causing disease
in certain plants. We study the interactions of P. syringae with such
crop plants as tobacco, soybeans, and tomato, as well as the interactions of P.
syringae with the genetically amenable plant Arabidopsis. Studying
the interaction of P. syringae and Arabidopsis. is particularly
attractive because it allows us to relatively easily identify key molecular
attributes of both the pathogen and the host with the long-term goal of
understanding the intimacies involved in bacterial parasitism.
Recent Papers
Jeong, B-r., K. van Dijk, and J.R. Alfano. 2009. Pseudomonas syringae type III-secreted proteins and their activities and effects on plant innate immunity. Annu. Plant Reviews. 34: 48-76.
Streitner, C., S. Danisman, F. Wehrle, J.C. Schoining, J.R. Alfano, and D. Staiger. 2008. The small glycine-rich RNA-binding protein AtGRP7 promotes floral transition in Arabidopsis thaliana. Plant J. 56: 239-250.
Block, A., G. Li, Z. Q. Fu, and J.R. Alfano. 2008. Phytopathogen type III effector weaponry and their plant targets. Curr. Opin. Plant Biol. 396-403.
Alvarez-Venegas, R., A.A. Abdallat, M. Guo, J.R. Alfano, and Z. Avramova. 2007. Epigenetic control of a transcription factor at the cross section of two antagonistic pathways. Epigenetics 2: 106-113.
Wei, C.-F., B.H. Kvitko, R. Shimizu, E. Crabill, J.R. Alfano, N.-C. Lin, G.B. Martin, H.-C. Huang, A. Collmer. 2007. A Pseudomonas syringae pv. tomato DC3000 mutant lacking the type III effector HopQ1-1 is able to cause disease in the model plant Nicotiana benthamiana. Plant J. 51: 32-46.
Fu, Z.Q., M. Guo, B. -r. Jeong, F. Tian, T. E. Elthon, R.L. Cerny, D. Staiger, and J. R. Alfano. 2007. A type III effector ADP-ribosylates RNA-binding proteins and quells plant immunity. Nature 447: 284-288.
Vencato, M., F. Tian, J. R. Alfano, C. R. Buell, S. Cartinhour, G. A. DeClerck, D. S. Guttman, J. Stavrinides, V. Joardar, M. Lindeberg, P. A. Bronstein, J. W. Mansfield, C. R. Myers, A. Collmer, and D. J. Schneider. 2006. Bioinformatics-enabled identification of the HrpL regulon and type III secretion system effector proteins of Pseudomonas syringae pv. phaseolicola 1448A. Mol. Plant Microbe Interact. 19: 1193-1206.
Fereirra, A.O., C.R. Myers, J.S. Gordon, G.B. Martin, M. Vencato, Alan Collmer, M.D. Wehling, J.R. Alfano, G. Moreno-Hagelsieb, W.F. Lamboy, G. DeClerck, D.J. Schneider, and S.W. Cartinhour. 2006. Whole-genome expression profiling defines the HrpL regulon of Pseudomonas syringae pv. tomato DC3000, allows de novo reconstruction of the Hrp cis element, and identifies novel co-regulated genes. Mol. Plant Microbe Interact. 19: 1167-1179.
Fu, Z.Q., M. Guo, and J.R. Alfano. 2006. The Pseudomonas syringae HrpJ is a type III-secreted protein that is required for plant pathogenesis, injection of effectors, and for secretion of the HrpZ1 harpin. J. Bacteriol. 188: 6060-6069.
Guo, M., S.T. Chancey, F. Tain, Z. Ge, Y. Jamir, and J.R. Alfano. 2005. Pseudomonas syringae type III chaperones ShcO1, ShcS1, and ShcS2 facilitate translocation of their cognate effectors and can substitute for each other in the secretion of HopO1-1. J. Bacteriol.187: 4257-4269.
Lindeberg, M., J. Stavrinides, J. H. Chang, J. R. Alfano, A. Collmer, J. L. Dangl, J. T. Greenberg, J. W. Mansfield, and D. S. Guttman. 2005. Proposed guidelines for a unified nomenclature and phylogenetic analysis of type III Hop effector proteins in the plant pathogen Pseudomonas syringae. Mol. Plant-Microbe Interact. 18: 275-282.
Petnicki-Ocwieja, T., K. van Dijk, and J. R. Alfano. The hrpK operon of Pseudomonas syringae pv. tomato DC3000 encodes two proteins secreted by the type III (Hrp) protein secretion system: HopB1 and HrpK, a putative type III translocator. 2005. J. Bacteriol. 187: 649-663.
Espinosa, A., and J. R. Alfano. 2004. Disabling surveillance: Bacterial type III secretion system effectors that suppress innate immunity. Cell. Microbiol. 6: 1027-1040.
Alfano, J. R., and A. Collmer. 2004. Type III secretion system effector proteins: Double agents in bacterial disease and plant defense. Annu. Rev. Phytopathol. 42:385-414.
Wehling, M. D., M. Guo, Z. Q. Fu, and J. R. Alfano. 2004. The Pseudomonas syringae HopPtoV protein is secreted in culture and translocated into plant cells via the type III protein secretion system in a manner dependent on the ShcV type III chaperone. J. Bacteriol. 186: 3621-3630.
Shan, L., H. -S. Oh, M. Guo, J. Zhou, J. R. Alfano, A. Collmer, and X. Tang. 2004. The hopPtoF locus of Pseudomonas syringae pv. tomato DC3000 encodes a type III chaperone and a cognate effector. Mol. Plant-Microbe Interact. 17: 447-455.
He, P., S. Chintamanani, Z. Chen, L. Zhu, B. N. Kunkel, J. R. Alfano, X. Tang, and J. -M. Zhou. 2004. Activation of a Coi1-dependent pathway in Arabidopsis by Pseudomonas syringae type III effectors and coronatine. Plant J. 37: 589-602.
Jamir, Y., M. Guo, H. -S. Oh, T. Petnicki-Ocwieja, S. Chen, X. Tang, M. B. Dickman, A. Collmer, and J. R. Alfano. 2004. Identification of Pseudomonas syringae type III effectors that can suppress programmed cell death in plants and yeast. Plant J. 37: 554-565.
Schechter, L. M., K. A. Roberts, Y. Jamir, J. R. Alfano, and A. Collmer. 2004. Pseudomonas syringae type III secretion system targeting signals and novel effectors studied with a Cya translocation reporter. J. Bacteriol. 186:543-555.
Chatterjee, A., Y. Cui, H. Yang, A. Collmer, J. R. Alfano, and A. K. Chatterjee. 2003. GacA, the response regulator of a two-component system, acts as a master regulator in Pseudomonas syringae pv. syringae DC3000 by controlling regulatory RNA, transcriptional activators, and alternate sigma factors. Mol. Plant-Microbe Interact. 16:1106-1117.
Buell, C. R., et. al. 2003. The complete sequence of the Arabidopsis and tomato pathogen Pseudomonas syringae pv. tomato DC3000. Proc. Natl. Acad. Sci. USA 100:10181-10186.
Espinosa, A., M. Guo, V. C. Tam, Z. Q. Fu, and J. R. Alfano. 2003. The Pseudomonas syringae type III-secreted protein HopPtoD2 possesses protein tyrosine phosphatase activity and suppresses programmed cell death in plants. Mol. Microbiol. 49: 377-397.
Collmer, A., M. Lindeberg, T. Petnicki-Ocwieja, D.J. Schneider, and J.R. Alfano. 2002. Genome mining type III secretion system effectors in Pseudomonas syringae yields new picks for all TTSS prospectors. Trends Microbiol. 10: 462-469.
van Dijk, K., V. C. Tam, A. R. Records, T. Petnicki-Ocwieja, and J. R. Alfano. 2002. The ShcA protein is a molecular chaperone that assists in the secretion of the HopPsyA effector from the type III (Hrp) protein secretion system of Pseudomonas syringae. Mol. Microbiol. 44: 1469-1481.
Petnicki-Ocwieja, T., D. J. Schneider, V. C. Tam, S. T. Chancey, L. Shan, Y. Jamir, L. M. Schechter, C. R. Buell. X. Tang, A. Collmer, and J. R. Alfano. 2002. Genomewide identification of proteins secreted by the Hrp type III protein secretion system of Pseudomonas syringae pv. tomato DC3000. Proc. Natl. Acad. Sci. USA. 99: 7652-7657.
Collmer, A., J. L. Badel, A. O. Charkowski, W. L. Deng, D. E. Fouts, A. R. Ramos, A. H. Rehm, D. M. Anderson, O. Schneewind, K. van Dijk, and J. R. Alfano. 2000. Pseudomonas syringae Hrp type III secretion system and effector proteins. Proc. Natl. Acad. Sci. USA. 97:8770-8777.
Alfano, J. R., A. O. Charkowski, W. L. Deng, T. Petnicki, K. van Dijk and A. Collmer. 2000. The Pseudomonas syringae Hrp pathogenicity island has a tripartite mosaic structure comprised of a cluster of type III genes bounded by an exchangeable effector and conserved effector loci that contribute to parasitic fitness and pathogenicity in plants. Proc. Natl. Acad. Sci. USA.97:4856-4861.
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