B.S., Biology, Johns Hopkins University
Ph.D., Biology, Yale University

My research group studies the interaction of plants with bacterial pathogens at the molecular level. These studies involve a model system for ease of genetic analysis as well as a system of importance to agriculture. The overall goal of our research is to improve our understanding of how plants resist bacterial pathogens and how bacterial pathogens cause disease in plants.

The model system we use is the interaction of Arabidopsis thaliana with the pathogen Pseudomonas syringae. Pseudomonas syringae causes bacterial speck disease on tomato plants, and it also causes the same disease on Arabidopsis. We have taken a genetic approach to studying Arabidopsis resistance to this pathogen. This has resulted in our discovery of the CPN1 gene. Mutations in the CPN1 gene make the plant more resistant to Pseudomonas syringae, apparently because the mutant plant constantly activates its disease resistance mechanisms. The CPN1 protein function to negatively regulate plant defense mechanisms, such as the hypersensitive cell death defense reaction. We are currently trying to dissect how the CPN1 protein may function in disease resistance and in pathogenesis.

The system of interest to agriculture that we are studying is the interaction of Erwinia amylovora with apple trees. Erwinia amylovora causes fire blight on pome fruits, a devastating systemic disease that can cause substantial crop and tree losses. In a collaboration with Dr. James Travis, we have investigated the impact of apple rootstocks on apple scions in terms of their fire blight resistance and gene expression patterns. We have discovered a number of apple genes that may be involved in fire blight resistance and determining tree stature.

Jambunathan, N., and McNellis, T. W. (2003) " Regulation of Arabidopsis COPINE 1 gene expression in response to pathogens and abiotic stimuli." Plant Physiol. 132, 1370-1381.

Jambunathan, N., Siani, J. M., and McNellis, T. W. (2001) "A humidity-sensitive Arabidopsis copine mutant exhibits precocious cell death and increased disease resistance." Plant Cell 13, 2225-2240.

*Axtell, M. J., *McNellis, T. W., Mudgett, M. B., Hsu, C. S., and Staskawicz, B. J. (2001) "Mutational analysis of the Arabidopsis RPS2 disease resistance gene and the corresponding Pseudomonas syringae avrRpt2 avirulence gene." MPMI 14, 181-188. *Co-first authors.

Stoop-Myer C., Torii K. U., McNellis T. W., Coleman J. E., and Deng X.-W. (1999) "The N-terminal fragment of Arabidopsis photomorphogenic repressor COP1 maintains partial function and acts in a concentration-dependent manner." Plant J. 20, 713-717.

McNellis, T. W., Mudgett, M. B., Li, K., Aoyama, T., Horvath, D., Chua, N.-H., and Staskawicz, B.J. (1998). "Glucocorticoid-inducible expression of a bacterial avirulence gene in transgenic Arabidopsis plants induces hypersensitive cell death." Plant J. 14, 247-257.

Torii, K. U., McNellis, T. W., and Deng, X.-W. (1998) "Functional dissection of Arabidopsis COP1 reveals specific roles of its three structural modules in light control of seedling development." EMBO J. 17, 5577-5587.

McNellis, T. W., Torii, K. U., and Deng, X.-W. (1996). "Expression of an N-terminal fragment of COP1 confers a dominant-negative effect on light-regulated seedling development in Arabidopsis." Plant Cell 8, 1491-1503.

McNellis, T. W., and Deng, X.-W. (1995)." Light control of seedling morphogenetic pattern." Plant Cell 7, 1749-1761.

McNellis, T. W., von Arnim, A. G., and Deng, X.-W. (1994). "Overexpression of Arabidopsis COP1 results in partial suppression of light-mediated development: Evidence for a light-inactivable repressor of photomorphogenesis." Plant Cell 6, 1391-1400.

McNellis, T. W., von Arnim, A. G., Araki, T., Komeda, Y., Misera, S., and Deng, X.-W. (1994)." Genetic and molecular analysis of an allelic series of cop1 mutants suggests functional roles for the multiple protein domains." Plant Cell 4, 487-500.

Wei, N., Kwok, S. F., von Arnim, A. G., Lee, A., McNellis, T. W., Piekos, B., and Deng, X.-W. (1994). "Arabidopsis COP8, COP10, and COP11 genes are involved in repression of photomorphogenic development in darkness." Plant Cell 6, 629-643.

Cheung, A. Y., McNellis, T., and Piekos, B. (1993)." Maintenance of chloroplast components during chromoplast differentiation in the tomato mutant green flesh." Plant Physiol. 101, 1223-1229.