This project uses the interaction between tomato leaves and Pseudomonas syringae as a model system to investigate the molecular basis of bacterial pathogenesis and host responses to bacterial infection. To understand bacterial pathogenesis, we focus on a key virulence protein, AvrPtoB, that is secreted into host cells by the bacterial type III secretion system. To explore the host response, we focus on the rapid programmed cell death (PCD) that is associated with plant immunity. We have found that AvrPtoB acts to suppress PCD in both plants and in yeast indicating that AvrPtoB likely targets a highly conserved eukaryotic process. AvrPtoB is a modular protein: the N-terminal domain interacts with the host kinase Pto to elicit immunity, whereas the C-terminus is required for PCD inhibition. In preliminary work, we have discovered that in the host cell AvrPtoB is likely ubiquitinated, cleaved, and the cleavage products are localized to different subcellular compartments. As part of a collaboration, the structure of the AvrPtoB anti-PCD domain has been solved and shown to have homology to E3 ubiquitin ligases; determination of the N-terminal structure is underway. Possible host targets of AvrPtoB anti-PCD activity, including MEK1, a MAPKK, have been identified. Finally, we have developed a gene silencing screen for use in identifying genes that play a role in host PCD. We propose to: 1) Investigate the role in pathogenesis of AvrPtoB post-translational modifications; 2) Determine if AvrPtoB is an E3 ubiquitin ligase; 3) Characterize the interaction of AvrPtoB with MEK1; 4) Examine the role of differential subcellular localization of AvrPtoB cleavage products; and 5) Use AvrPtoB to identify novel components of host PCD pathways. Our research takes advantage of two experimentally tractable organisms to elucidate host PCD and an important pathogen virulence mechanism, PCD-suppression, - processes which impact both plant agriculture and human health. Our studies are relevant to U.S. biosecurity concerns because type III effector proteins, such as AvrPtoB, occur in many potentially weaponizable human pathogens such as Yersinia and understanding their virulence mechanisms could lead to specific intervention strategies. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM078021-03
Application #
7420945
Study Section
Host Interactions with Bacterial Pathogens Study Section (HIBP)
Program Officer
Anderson, James J
Project Start
2006-05-01
Project End
2010-04-30
Budget Start
2008-05-01
Budget End
2009-04-30
Support Year
3
Fiscal Year
2008
Total Cost
$211,797
Indirect Cost
Name
Boyce Thompson Institute for Plant Research
Department
Type
DUNS #
045666088
City
Ithaca
State
NY
Country
United States
Zip Code
14853
Wei, Hai-Lei; Chakravarthy, Suma; Mathieu, Johannes et al. (2015) Pseudomonas syringae pv. tomato DC3000 Type III Secretion Effector Polymutants Reveal an Interplay between HopAD1 and AvrPtoB. Cell Host Microbe 17:752-62
Mathieu, Johannes; Schwizer, Simon; Martin, Gregory B (2014) Pto kinase binds two domains of AvrPtoB and its proximity to the effector E3 ligase determines if it evades degradation and activates plant immunity. PLoS Pathog 10:e1004227
Chien, Ching-Fang; Mathieu, Johannes; Hsu, Chun-Hua et al. (2013) Nonhost resistance of tomato to the bean pathogen Pseudomonas syringae pv. syringae B728a is due to a defective E3 ubiquitin ligase domain in avrptobb728a. Mol Plant Microbe Interact 26:387-97
Clarke, Christopher R; Chinchilla, Delphine; Hind, Sarah R et al. (2013) Allelic variation in two distinct Pseudomonas syringae flagellin epitopes modulates the strength of plant immune responses but not bacterial motility. New Phytol 200:847-60
Mural, Ravi V; Liu, Yao; Rosebrock, Tracy R et al. (2013) The tomato Fni3 lysine-63-specific ubiquitin-conjugating enzyme and suv ubiquitin E2 variant positively regulate plant immunity. Plant Cell 25:3615-31
Zeng, Lirong; Velasquez, Andre C; Munkvold, Kathy R et al. (2012) A tomato LysM receptor-like kinase promotes immunity and its kinase activity is inhibited by AvrPtoB. Plant J 69:92-103
Cheng, Wei; Munkvold, Kathy R; Gao, Haishan et al. (2011) Structural analysis of Pseudomonas syringae AvrPtoB bound to host BAK1 reveals two similar kinase-interacting domains in a type III Effector. Cell Host Microbe 10:616-26
Dong, Jing; Xiao, Fangming; Fan, Fenxia et al. (2009) Crystal structure of the complex between Pseudomonas effector AvrPtoB and the tomato Pto kinase reveals both a shared and a unique interface compared with AvrPto-Pto. Plant Cell 21:1846-59
Munkvold, Kathy R; Martin, Gregory B (2009) Advances in experimental methods for the elucidation of Pseudomonas syringae effector function with a focus on AvrPtoB. Mol Plant Pathol 10:777-93
Shan, Libo; He, Ping; Li, Jianming et al. (2008) Bacterial effectors target the common signaling partner BAK1 to disrupt multiple MAMP receptor-signaling complexes and impede plant immunity. Cell Host Microbe 4:17-27

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