Pathogen pressure exerts a major drag on crop yields.  The outcomes of plant-pathogen interactions are determined by a fascinating complex interplay between pathogen efforts to extract nutrients from plant hosts and host efforts to prevent this.  Major host and pathogen genes that play roles in these interactions are subject to ongoing selection as both pathogens and hosts evolve improved mechanisms for attack and defense.

We use a genetic approach to understanding plant defenses against pathogen attack. Plant mutants with defects in disease resistance are isolated and characterized, revealing the mechanisms underlying effective defense.  Most of our work involves the reference plant Arabidopsis thaliana, which enables us to take advantage of powerful genetic and genomic resources available for this organism.  In much of our work we use the bacterial pathogen Pseudomonas syringae.  Growth of this hemi-biotrophic pathogen is limited by two main sectors of the defense network.  One sector triggers defenses by host recognition of pathogen-associated molecular patterns (PAMPs), while the other triggers defenses through the salicylic acid (SA)-dependent network sector.  We also study defenses against the necrotrophic fungal pathogen Alternaria brassicicola.  Effective defense against his pathogen depends on production of the small anti-microbial molecule camalexin, as well as on the jasmonic acid-dependent network sector.  By studying responses to both of these pathogens, we hope to obtain a broad view of the plant defense network.  Presently, there are three main foci of our work.

1. We have recently discovered that, in Arabidopsis, members of the calmodulin-binding protein 60 (CBP60) family play important roles in signaling during responses to pathogens.  Current work aims to understand the differential roles of family members, and the mechanisms by which these proteins affect activation of salicylic acid-dependent defenses.  Salicylic acid-dependent defenses are critical for effective defense against biotrophic pathogens.
2. We are studying responses to the fungal necrotroph Alternaria brassicicola.  From a metabolite profiling experiment, we have identified several metabolites that promote or restrict fungal growth.  Very recently, we have begun testing the effects of alterations in plant cell walls on plant susceptibility to various pathogens.  This could become important as crops with altered cell walls are bred for production of biofuels.
3. We are identifying pathogen proteins that are secreted into host cells from the wheat pathogen, Puccinia graminis pv. tritici.  This work will ultimately lead to efforts to improve wheat resistance to this important pathogen.

We are grateful to NSF, DOE Biosciences, and the 2 Blades foundation for funding our work.

Jung, H.W., Tschaplinski, T., Wang, L., Glazebrook, J., and Greenberg, J.T. A pathogen-induced primer of systemic plant immunity. Science.  324:89-91 (2009).

Wang, L., Tsuda, K., Sato, M., Cohen, J.D., Katagiri, F., and Glazebrook, J.  Arabidopsis CaM binding protein CBP60g contributes to MAMP-induced SA accumulation and is involved in disease resistance against Pseudomonas syringae.  PLoS Pathogens, 5(2): e1000301. doi:10.1371/journal.ppat.1000301 (2009).

Wang, L., Mitra, R., Hasselmann, K.D., Sato, M., Lenarz-Wyatt, L., Cohen, J.D., Katagiri, F., and Glazebrook, J.  The Genetic Network Controlling the Arabidopsis Transcriptional Response to Pseudomonas syringae pv. maculicola: Roles of Major Regulators and the Phytotoxin Coronatine.  Mol. Plant-Microbe. Int. 21:1408-1420 (2008).

Qiu, J.-L., Fiil, B.K., Petersen, K., Nielsen, H.B., Botanga, C.J., Thorgrimsen, S., Palma, K., Suarez-Rodriguez, M. C., Sandbech-Clausen, S., Lichota, J., Brodersen, P., Grasser, K.D., Mattsson, O., Glazebrook, J., Mundy, J., and Petersen, M.  Arabidopsis MAP Kinase 4 Regulates Gene Expression Via Transcription Factor Release in the Nucleus.  EMBO J. 27:2214-2221 (2008).

Ren, D., Liu, Y., Yang, K.-W., Han, L., Mao, G., Glazebrook, J., and Zhang, S. A Fungal-Responsive Mitogen-Activated Protein Kinase Cascade Regulates Phytoalexin Biosynthesis in Arabidopsis.  Proc. Natl. Acad. Sci USA 105: 5638-5643 (2008).

Tsuda, K., Sato, M., Glazebrook, J., Cohen, J.D., and Katagiri, F. Interplay Between MAMP-Triggered and SA-Mediated Defense Responses.  Plant J. 53:763-775 (2008).

Nafisi, M., Goregaoker, S., Botanga, C.J., Glawischnig, E., Olsen, C.E., Halkier, B.A. and Glazebrook, J.  Arabidopsis Cytochrome P450 Monooxygenase 71A13 Catalyzes the Conversion of Indole-3-Acetaldoxime in Camalexin Synthesis.  Plant Cell 19:2039-2052 (2007).

Sato, M., Mitra, R.M., Coller, J., Wang, D., Spivey, N.W., Dewdney, J., Denoux, C., Glazebrook, J., and Katagiri, F.  A High-Performance, Small-Scale Microarray for Expression Profiling of Many Samples in Arabidopsis-Pathogen Studies.  Plant J. 49:565-577 (2007).

Parisy, V., Poinssot, B., Owsianowski, L., Buchala, A., Glazebrook, J., and F. Mauch.  Identification of PAD2 as a ?-Glutamylcysteine Synthetase Highlights the Importance of Glutathione in Disease Resistance of Arabidopsis.  Plant J. 49:159-172 (2007).