Research Summary

My broad interest is in how organisms adapt to a changing environment. I study this in the context of host-pathogen interactions using the model system of the plant Arabidopsis thaliana and the gram negative pathogen Pseudomonas syringae. In response to infection, plants mount a complex defense response involving cell suicide, the crosslinking of cell wall components, antibiotic production and defense gene activation. We discovered that infection also activates cell growth and the cell cycle. We study how Arabidopsis regulates its defense and cell death response to pathogens using mutants, which express one or more aspects of the defense response in the absence of pathogens. We focus on a particular class of mutants, which show cell suicide and defense responses when no pathogen is present. We call these mutants acd for accelerated cell death. We use a collection of these mutants in two ways. First, we try to learn about defense signaling and cell death control using these mutants in combination with other mutations that affect specific aspects of plant defense. Second, we clone the genes identified by the mutations in order to gain insights into the molecular basis for the mutant phenotypes and as reagents for doing biochemical and cell biological studies on the mechanism of gene action. We also studying virulence proteins secreted by pathogenic bacteria by a specialized type III secretion system directly into plant cells. We do structure-function analysis on known secreted proteins (called effectors) to determine how they function to exert their virulence, we study the role of effectors in host range restriction and we study the localization and host targets of effectors.

Selected Publications

Vinatzer BA, Teitzel GM, Lee M-W, Jelenska J, Hotton S, Fairfax K, Jenrette J, and Greenberg JT. (2006). The Type III effector repertoire of Pseudomonas syringae pv. syringae B728a and its role in survival and disease on host and non-host plants. Mol. Micro. 62:26-44. (PubMed)

Yao, N. and Greenberg, JT. Arabidopsis ACCELERATED CELL DEATH2 Modulates Programmed Cell Death. Plant Cell. 2006 18:397-411. (PubMed)

Yao, N., Eisfelder, B. J., Marvin, J. and Greenberg, J.T. (2004) The mitochondrion, an organelle commonly involved in programmed cell death in Arabidopsis thaliana. Plant J. 40:596-610. (PubMed)

Song, J. T., Lu, H., McDowell, J. M. and Greenberg, J. T. (2004). "A key role for ALD1 in activation of local and systemic defenses in Arabidopsis." Plant J 40: 200-12. (PubMed)

Song, J. T., Lu, H. and Greenberg, J. T. (2004). "Divergent roles in Arabidopsis thaliana development and defense of two homologous genes, aberrant growth and death2 and AGD2-LIKE DEFENSE RESPONSE PROTEIN1, encoding novel aminotransferases." Plant Cell 16: 353-66. (PubMed)

Liang, H., Yao, N., Song, J. T., Luo, S., Lu, H. and Greenberg, J. T. (2003). "Ceramides modulate programmed cell death in plants." Genes Dev 17: 2636-41. (PubMed)

Lu, H., Rate, D. N., Song, J. T. and Greenberg, J. T. (2003). "ACD6, a novel ankyrin protein, is a regulator and an effector of salicylic acid signaling in the Arabidopsis defense response." Plant Cell 15: 2408-20. (PubMed)

Guttman, D. S., Vinatzer, B. A., Sarkar, S. F., Ranall, M. V., Kettler, G. and Greenberg, J. T. (2002). "A functional screen for the type III (Hrp) secretome of the plant pathogen Pseudomonas syringae." Science 295: 1722-6. (PubMed)