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Plant Biology Forum of IOB - the 55th lecture
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Title of the lecture:  Functional Dissection of LRR-Kinase Receptors and Plant Defense Signaling
Speaker: Andrew Bent, Professor
    Department of Plant Pathology, University of Wisconsin - Madison, USA
Time:  14:30 on  Mar.9, 2010
Location: Multi-functional Conference Hall inTuzi building, Institute of Botany, Chinese Academy of Sciences, Beijing, China
Contact:  Prof.Chunming Liu (cmliu@ibcas.ac.cn)

 Sponsor: 
The Key Laboratory of Photosynthesis & Environmental Molecular Physiology, CAS/The Key Laboratory of Plant Molecular Physiology, CAS 

Brief CV of speaker:
   Prof. Andrew F. Bent. Ph.D MIT
   We are investigating multiple topics related to plant disease resistance and to the functional mechanics of proteins with LRR (leucine-rich repeat) domains. We have been studying FLS2, a transmembrane LRR-kinase protein that is the plant receptor of bacterial flagellin, as well as EFR, the plant receptor LRR-kinase for bacterial EF-Tu. Our dissection of specific receptor sub-domains and their contributions to signaling and to protein-protein interactions will be discussed. An algorithm will be described that detects regions of conservation on the predicted surface of folded LRR domains as a means to identify candidate functional domains within the LRR. Specificity for different flagellin variants is one aspect of these studies. Lastly, our work on the roles of poly(ADP-ribosyl)ation in the defense signaling pathways elicited by flagellin or EF-Tu will be described briefly. 
Our work examines plant disease resistance and the molecular basis of plant resistance to infection by microbial pathogens. The plant immune system includes some components that are conserved with animals, and a number of capacities that are unique to plants. We study disease resistance in part because host-pathogen dynamics and the molecular workings of immune systems are fascinating biological topics. We also study this because on a practical level, one of the best ways to control plant diseases is through use of genetically determined resistance. This approach is convenient for the grower and minimizes the need for costly, time-consuming and/or potentially toxic external treatments. Plant breeders have utilized disease resistance genes in cultivar development for literally thousands of years, but the molecular basis of this resistance is only partly understood. Identification and study of the plant genes and the biochemical/cellular processes that control disease resistance can bring us closer to understanding the basic mechanisms of pathogen recognition, defense signal transduction and activation of resistance responses. These discoveries also foster the development of specific approaches for improvement of disease resistance. 
Much of the work in our laboratory examines Arabidopsis thaliana because of the extraordinary experimental versatility of this plant species. We also study soybean, Brassica and other plant species. We work with many different pathogens, but most typically study Pseudomonas syringae pv. tomato and Xanthomonas campestris pv. campestris. 
We are presently focused on three projects: 

1) Leucine-rich repeat (LRR) structure/function, and plant detection of bacterial flagellin. 

We are developing ways to identify and manipulate LRR active sites within plant disease resistance proteins and other LRR proteins. The flagellin receptor FLS2 of Arabidopsis is our primary model. We are working to understand how ligand specificity is determined, and how it can be altered in a targeted way by in vitro evolution. We are also examining the ways in which some bacterial pathogens have evolved to escape plant detection of their flagellins. 

2) Study and manipulation of disease resistance in soybean. 

Agrobacterium rhizogenes-mediated root transformation and other methods are being used to facilitate molecular genetic dissection of soybean disease resistance. This includes a new, collaborative effort to nail down the nature of the rhg1 and Rhg4 genes that confer significant resistance to soybean cyst nematode. 

3) Previously unidentified biochemical responses of plants to pathogen infection 

Using microarray expression profiling data as a starting point, and Arabidopsis gene knockout plant lines for initial tests, we have identified relatively unexamined aspects of the plant response to pathogens. We are now conducting further study of the identified pathways, for example, the role of poly(ADP-ribosyl)ation in plant responses to infection. 

Selected Recent Publications 

Adams-Phillips, L., A.G. Briggs and A.F. Bent, 2009. Disruption of poly(ADP-ribosyl)ation mechanisms alters responses of Arabidopsis thaliana to biotic stress. Plant Physiol. 152:267-280.PDF 

Allen, C., A. Bent and A. Charkowski, 2009. Underexplored niches in research on plant pathogenic bacteria. Plant Physiol. 150:1631-1637.PDF 

Genger, R.K., G.I. Jurkowski, J.M. McDowell, H. Lu, H.W. Jung, J.T. Greenberg and A.F. Bent, 2008. ">Signaling pathways that regulate the enhanced disease resistance of Arabidopsis "defense, no death" mutants. Mol. Plant-Microbe Interact. (in press)PDF 

Adams-Phillips. L., J. Wan, X. Tan, F.M. Dunning, B.C. Meyers, R.W. Michelmore and A.F. Bent, 2008. Discovery of ADP-ribosylation and other plant defense pathway elements through expression profiling of four different Arabidopsis-Pseudomonas R/avr interactions. Mol. Plant-Microbe Interact. 21:646-657. PDF PubMed 

Dunning, F.M., W. Sun, K.L. Jansen, L. Helft and A.F. Bent, 2007. Identification and mutational analysis of Arabidopsis FLS2 Leucine-Rich Repeat domain residues that contribute to flagellin perception. Plant Cell. 19:3297-3313. PDF PubMed 

Bent, A. and D. Mackey, 2007. Elicitors, Effectors and R Genes: The new paradigm and a lifetime supply of questions. Annu. Rev. Phytopathol. 45:399-436. PDF PubMed 

Suarez-Rodriguez MC, Adams-Phillips L, Liu Y, Wang H, Su SH, Jester PJ, Zhang S, Bent AF, Krysan PJ, 2006. MEKK1 Is Required for flg22-induced MPK4 Activation in Arabidopsis Plants. Plant Physiol. 143:661-669. PDF PubMed 

Sun, W., F.M. Dunning, C. Pfund, R. Weingarten and A.F. Bent, 2006. Within-species flagellin polymorphism in Xanthomonas campestris pv. campestris and its impact on elicitation of Arabidopsis FLS2-dependent defenses. Plant Cell 18:764-779. PDF PubMed 

Bent, A.F., T.K. Hoffman, J.S. Schmidt, G.L. Hartman, D.D. Hoffman, X. Ping, M.L. Tucker, 2006. Disease- and Performance-Related Traits of Ethylene-Insensitive Soybean. Crop Science 43:893-901. PDF Abstract

Bent, A.F., 2006. Arabidopsis thaliana Floral Dip Transformation Method. In: Agrobacterium Protocols - 2 nd Edition (K. Wang, Ed.). Methods in Molecular Biology Book Series, Humana Press, Totowa, NJ. Methods in Molecular Biology 343:87-103. PubMed 

Quirino, B.F., R. Genger, J.H. Ham, G. Zabala and A.F. Bent, 2004. Identification and functional analysis of Arabidopsis proteins that interact with resistance gene product RPS2 in yeast. Physiol. Molec. Plant Pathol. 65:257-267. PDF Abstract 

Jurkowski, G. I., R.K. Smith, I.-c. Yu, J.H. Ham, S.B. Sharma, D.F. Klessig, K.A. Fengler and A.F. Bent, 2004. Arabidopsis DND2, a second cyclic nucleotide-gated ion channel gene for which mutation causes the "defense, no death" phenotype. Mol. Plant-Microbe Interact. 17:511-520. PDF PubMed 

Pfund, C., J. Tans-Kersten, J., F.M. Dunning, J.M. Alonso, J.R. Ecker, C. Allen and A.F. Bent, 2004. Flagellin is not a major defense elicitor in Ralstonia solanacearum cells or extracts applied to Arabidopsis thaliana. Mol. Plant-Microbe Interact. 17:696-706. PDF PubMed 

Chan, C., R. K. Smith, A. F. Bent and M. Sussman, 2003 A cyclic nucleotide-gated ion channel, CNGC2, is crucial for plant development and adaptation to calcium stress. Plant Physiology 132:728-731. PDF PubMed 

Quirino, B. F. and A. F. Bent (2003) Deciphering host resistance and pathogen virulence: The Arabidopsis/Pseudomonas interaction as a model. Mol. Plant Pathol. 4:517-530. PDF Abstract 

Wan, J., F.M. Dunning and A. F. Bent, 2002. Probing plant-pathogen interactions and downstream defense signaling using DNA microarrays. Funct. & Integr. Genomics 2: 259-273. PDF PubMed 

Bent, A. F., 2002. "Crop Diseases and Strategies for their Control." Chapter 15 In: Plants, Genes and Agriculture, 2nd Ed. M. Chrispeels and D. Sadava, Eds., Jones and Bartelett, Inc., Sudbury, MA, pp. 390-413. 

Bent. A. F., 2002. "Reconnecting Farms and Ecosystems, If It Pays." Review of the book: The Farm as Natural Habitat: Reconnecting Farm Systems with Ecosystems (D. L. Jackson and L. L. Jackson, eds., Island Press, Washington D.C., 2002). Science 298:1340-1341. PDF 

Bent, A. F., 2001. Plant mitogen-activated protein kinase cascades: Negative regulatory roles turn out positive (Commentary). Proc. Natl. Acad. Sci. (USA) 98:784-786. PDF PubMed 

M.S. Bachman, J.P. Tamulonis, C.D. Nickell, and A.F. Bent. 2001. Molecular markers linked to brown stem rot resistance genes, Rbs1 and Rbs2, in soybean. Crop Sci. 41:527-535. PDF 

Banerjee, D., Z. Zhang, and A.F. Bent (2001). The LRR domain can determine effective interaction between RPS2 and other host factors in Arabidopsis RPS2-mediated disease resistance. Genetics 158:439-450. PDF PubMed 

Bent, A. F., 2000. Arabidopsis in planta transformation: Uses, mechanisms, and prospects for transformation of other species [invited Update for special issue on Arabidopsis]. Plant Physiol. 124:1540-1547. PubMed 

Clough, S. J., K. A. Fengler, B. Lippok, R. K. Smith Jr., I.-c. Yu, and A. F. Bent, 2000. The Arabidopsis dnd1 "defense, no death" gene encodes a mutated cyclic nucleotide-gated ion channel. Proc. Natl. Acad. Sci (USA) 97:9323-9328. PubMed 

Desfeux, C., S. J Clough and A. F. Bent, 2000. Female reproductive tissues are the primary target of Agrobacterium-mediated transformation by the Arabidopsis floral-dip method. Plant Physiol. 123:895-904 PubMed 

Yu, I.-c., K. A. Fengler, S. J. Clough and A. F. Bent, 2000. Identification of Arabidopsis mutants exhibiting an altered hypersensitive response in gene-for-gene disease resistance. Mol. Plant-Microbe Interact. 13:277-286. PubMed

 Hoffman, T., J. S. Schmidt, X. Zhang and A. F. Bent, 1999. Isolation of ethylene-insensitive soybean mutants that are altered in pathogen susceptibility and gene-for-gene disease resistance. Plant Physiology 119:935-950. PubMed

 Schmidt, J. S., J. E. Harper, T. K. Hoffman, and A. F. Bent, 1999. Regulation of soybean nodulation independent of ethylene signaling. Plant Physiology 119:951-960. PubMed

 Yu, I.-c., J. Parker and A. F. Bent, 1998. Gene-for-gene disease resistance without the hypersensitive response in Arabidopsis dnd1 mutant. Proc. Natl. Acad. Sci. USA 95:7819-7824. PubMed

 Clough, S. J. and A. F. Bent, 1998. Floral dip: a simplified method for Agrobacterium -mediated transformation of Arabidopsis thaliana. Plant J. 16:735-743. PubMed

 Lee, J.-M., G. L. Hartman, L. L. Domier, and A. F. Bent, 1996. Identification and map location of TTR1, a single locus in Arabidopsis thaliana that confers tolerance to tobacco ringspot nepovirus. Mol. Plant-Microbe Interact. 9:729-735. PubMed

 Bent, A. F., B. N. Kunkel, D. Dahlbeck, K. L. Brown, R. Schmidt, J. Giraudat, J. Leung, and B. J. Staskawicz, 1994. RPS2 of Arabidopsis thaliana: A leucine-rich repeat class of plant disease resistance genes. Science 265:1856-1860. PubMed

 Bent, A. F., and I.-c. Yu, 1999. Applications of Molecular Biology to Plant Disease and Insect Resistance. Advances in Agronomy 66:251-298.

 Bent, A. F., 1996. Plant disease resistance genes: Function meets structure. Plant Cell 8:1757-1771.

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