Brian Traw

Fig. 1 (A) Bacteria collected from Arabidopsis thaliana growing in nature (Traw et al. 2007). (B) Caterpillars caged on individual leaves.Our lab studies how wild plants interact with bacteria and other enemies (Fig. 1).  In agriculture, bacterial pathogens cause significant destruction of crops and necessitate extensive use of antibiotics.  How is it that some wild plants are able to resist infection by these pathogens?  If we can identify the resistance mechanisms of wild plants, we can use this knowledge to improve the resistance of crops and reduce antibiotic use in agriculture.

Specifically, our lab is addressing the following questions: 

1. Why do wild plants differ so greatly in their susceptibility to bacterial pathogens?
2. To what extent is defense of these plants dependent on constitutive or induced production of salicylic acid or other small metabolites
3. Are there geographic or temporal patterns that increase plant exposure to bacterial pathogens in nature?

Our Recent Findings:

We have discovered that some wild genotypes of Arabidopsis thaliana are dramatically more resistant to infection by the virulent bacterial pathogen, Pseudomonas syringae pv. tomato DC3000.  We have use genome wide association mapping (Fig. 2) to identify candidate genes that may explain this variation in resistance.  Our top candidates are membrane transporters, for which we have obtained knockouts and found corroborating evidence of strong role in defense.

Fig. 2 Genome-wide association map showing candidate loci for resistance to virulent Pst DC3000 in Arabidopsis (Traw et al, unpublished data). Above dashed line is significant at P<0.001.

Our Current Research:

First, to determine the functions of our candidate resistance genes, we are silencing these genes in the resistant genotypes to determine whether resistance is lost.   Second, to further assess the effects of these putative resistance alleles, we are inserting them into susceptible lines to determine whether resistance increases.  Third, given the suspected roles of some of these candidates in membrane transport of small metabolites, we are screening these plants for differences in metabolite production.  Finally, based on our predictions regarding the relationship of defense and growth temperature (Traw & Bergelson 2010), we are assessing geographic patterns in plant resistance in the worldwide collection of genotypes of Arabidopsis and other plants.

Collectively, our work encompasses a broad range of activity from lab bench to field work, from microscopy to liquid chromatography.  Students in the lab are encouraged to develop their own projects in these and other areas related to plant - enemy interactions.

Recent Publications

• Cantor, A., A. Hale, J. Aaron, M.B. Traw, and S. Kalisz (2011) Low allelochemical concentrations detected in garlic mustard-invaded forest soils can inhibit fungal growth and AMF spore germination. Biol Invasions :In Press

• Traw, M.B., and N. Gift (2010) Environmental microbiology: tannins & microbial decomposition of leaves on the forest floor. Am Biol Teach 72:506-512

• Todesco, M., S. Balasubramanian, T.T. Hu, M.B. Traw, M. Horton, P. Epple, C. Kuhns, S. Sureshkumar, C. Schwartz, C. Lanz, R.A. Laitinen, Y. Huang, J. Chory, V. Lipka, J.O. Borevitz, J.L. Dangl, J. Bergelson, M. Nordborg, and D. Weigel (2010) Natural allelic variation underlying a major fitness trade-off in Arabidopsis thaliana. Nature 465:632-636

• Traw, M.B., and J. Bergelson (2010) Plant immune system incompatibility and the distribution of enemies in natural hybrid zones. Curr Opin Plant Biol :

• Atwell, S., Y.S. Huang, B.J. Vilhjalmsson, G. Willems, M. Horton, Y. Li, D. Meng, A. Platt, A.M. Tarone, T.T. Hu, R. Jiang, N.W. Muliyati, X. Zhang, M.A. Amer, I. Baxter, B. Brachi, J. Chory, C. Dean, M. Debieu, J. de Meaux, J.R. Ecker, N. Faure, J.M. Kniskern, J.D. Jones, T. Michael, A. Nemri, F. Roux, D.E. Salt, C. Tang, M. Todesco, M.B. Traw, D. Weigel, P. Marjoram, J.O. Borevitz, J. Bergelson, and M. Nordborg (2010) Genome-wide association study of 107 phenotypes in Arabidopsis thaliana inbred lines. Nature :

• Mukherjee, M., K.E. Larrimore, N.J. Ahmed, T.S. Bedick, N.T. Barghouthi, M.B. Traw, and C. Barth (2010) Ascorbic acid deficiency in arabidopsis induces constitutive priming that is dependent on hydrogen peroxide, salicylic acid, and the NPR1 gene. Mol Plant Microbe Interact 23:340-351

• Bakker, E.G., M.B. Traw, C. Toomajian, M. Kreitman, and J. Bergelson (2008) Low levels of polymorphism in genes that control the activiation of defense response in Arabidopsis thaliana. Genetics 178:2031-2043

• Traw, M.B., and P. Feeny (2008) Glucosinolates and trichomes track tissue value in two sympatric mustards. Ecology 89:763-772

• Kniskern, J.M., M.B. Traw, and J. Bergelson (2007) Salicylic acid and jasmonic acid signaling defense pathways reduce natural bacterial diversity on Arabidopsis thaliana. Mol. Plant Microbe Interact. 20:1512-1522

• Traw, M.B., J.M. Kniskern, and J. Bergelson (2007) Sar increases fitness of Arabidopsis thaliana in the presence of natural bacterial pathogens. Evolution 61:2444-2449

• Morris, W.F., M.B. Traw, and J. Bergelson (2006) On testing for a tradeoff between constitutive and induced resistance. Oikos 112:102-110

• Aranzana, M.J., S. Kim, K Zhao, E. Bakker, M. Horton, K. Jakob, C. Lister, J. Molitor, C. Shindo, C. Tang, C. Toomajian, M.B. Traw, H. Zheng, J. Bergelson, C. Dean, P. Marjoram, and P. Nordberg (2005) Genome-wide association mapping in Arabidopsis identifies previously known flowering time and pathogen resistance genes. PLoS Genet. 1:531-539

• Cipollini, D., S. Enright, M.B. Traw, and J. Bergelson (2004) Salicylic acid inhibits jasmonic acid-induced resistance of Arabidopsis thaliana to Spodoptera exigua. Mol. Ecol. 13:1643-1653

• Traw, M.B., J. Kim, S. Enright, D.F. Cipollini, and J. Bergelson (2003) Negative cross-talk between salicylate- and jasmonate-mediated pathways in the Wassilewskija ecotype of Arabidopsis thaliana. Mol. Ecol. 12:1125-1135

• Tian, D., M.B. Traw, J.Q. Chen, M. Kreitman, and J. Bergelson (2003) Fitness costs of R-gene-mediated resistance in Arabidopsis thaliana. Nature 423:74-77

• Hao Ji, Graduate Student

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