Bacterial pathogens of plant and animals use the type III secretion (T3S) system and effector protein substrates to alter eukaryotic physiology to promote bacterial multiplication and host colonization. The large repertoire of T3S effectors (~20-30 proteins) in plant pathogenic bacteria predicts that multiple nodes in plant signaling cascades are being targeted. The identity of the plant targets and the biochemical mechanisms by which these T3S effector proteins manipulate plant physiology however are poorly understood. Extensive phenotypic studies support the concept that many of the T3S effectors suppress the plant immune system to colonize tissues. This illuminates the importance of basal defense responses and resistance (R) protein-mediated innate immune responses in controlling the outcome of bacterial infections in the plant kingdom. Understanding how plant immunity is regulated and how bacterial pathogens manipulate their hosts is fundamental knowledge required for the prevention and elimination of plant disease. The long-term goal of this project is elucidate how plants integrate lipid signals to respond to bacterial infection. Two conserved eukaryotic proteins - SOBER1, a lipase and CIP, a putative apolipoprotein - have been identified and shown to be important regulators of innate immune responses in plants. Comprehensive genetic and biochemical studies will be performed using the Arabidopsis pathosystem to characterize SOBER1 and CIP substrate specificity and to determine the mechanisms by which these proteins control phospholipid metabolism and signaling during bacterial infection. Studies will also be aimed to determine the biochemical mechanisms by which the pathogen T3S effector AvrBsT perturbs lipid homeostasis within infected plant cells. This work is expected to provide fundamental insight to the biochemical mechanisms used by plants to control lipid metabolism and signaling in response to pathogen attack. The growing body of evidence suggesting an interplay between lipid metabolism and immunity in both plants and animals indicates that fundamental knowledge about how lipid signals are initiated and terminated will be essential to fully understand how the immune system is regulated in eukaryotes.

Public Health Relevance

Understanding how plant immunity is regulated and how bacterial pathogens manipulate their hosts is fundamental knowledge required for the prevention and elimination of plant disease.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Host Interactions with Bacterial Pathogens Study Section (HIBP)
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Gindhart, Joseph G
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Stanford University
Schools of Arts and Sciences
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Kim, Jung-Gun; Stork, William; Mudgett, Mary Beth (2016) Quantification of Ethylene Production in Tomato Leaves Infected by Xanthomonas euvesicatoria. Bio Protoc 6:
Stork, William; Kim, Jung-Gun; Mudgett, Mary Beth (2015) Functional Analysis of Plant Defense Suppression and Activation by the Xanthomonas Core Type III Effector XopX. Mol Plant Microbe Interact 28:180-94
Fan, Min; Bai, Ming-Yi; Kim, Jung-Gun et al. (2014) The bHLH transcription factor HBI1 mediates the trade-off between growth and pathogen-associated molecular pattern-triggered immunity in Arabidopsis. Plant Cell 26:828-41
Cheong, Mi Sun; Kirik, Angela; Kim, Jung-Gun et al. (2014) AvrBsT acetylates Arabidopsis ACIP1, a protein that associates with microtubules and is required for immunity. PLoS Pathog 10:e1003952
Magnani, Enrico; de Klein, Niek; Nam, Hye-In et al. (2014) A comprehensive analysis of microProteins reveals their potentially widespread mechanism of transcriptional regulation. Plant Physiol 165:149-59
Kim, Jung-Gun; Stork, William; Mudgett, Mary Beth (2013) Xanthomonas type III effector XopD desumoylates tomato transcription factor SlERF4 to suppress ethylene responses and promote pathogen growth. Cell Host Microbe 13:143-54
Sonnewald, Sophia; Priller, Johannes P R; Schuster, Julia et al. (2012) Regulation of cell wall-bound invertase in pepper leaves by Xanthomonas campestris pv. vesicatoria type three effectors. PLoS One 7:e51763
Kim, Jung-Gun; Taylor, Kyle W; Mudgett, Mary Beth (2011) Comparative analysis of the XopD type III secretion (T3S) effector family in plant pathogenic bacteria. Mol Plant Pathol 12:715-30
Chen, Li-Qing; Hou, Bi-Huei; Lalonde, Sylvie et al. (2010) Sugar transporters for intercellular exchange and nutrition of pathogens. Nature 468:527-32
Kirik, Angela; Mudgett, Mary Beth (2009) SOBER1 phospholipase activity suppresses phosphatidic acid accumulation and plant immunity in response to bacterial effector AvrBsT. Proc Natl Acad Sci U S A 106:20532-7

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