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The AvrM Effector from Flax Rust Has a Structured C-Terminal Domain and Interacts Directly with the M Resistance Protein

January 2010 , Volume 23 , Number  1
Pages  49 - 57

Ann-Maree Catanzariti,1 Peter N. Dodds,2 Thomas Ve,3 Bostjan Kobe,3 Jeffrey G. Ellis,2 and Brian J. Staskawicz1

1Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley 94720-3102, U.S.A.; 2Commonwealth Scientific and Industrial Research Organisation, Division of Plant Industry, GPO Box 1600, Canberra ACT 2601, Australia; 3School of Chemistry and Molecular Biosciences and Institute for Molecular Bioscience, University of Queensland, Brisbane QLD 4072, Australia

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Accepted 4 September 2009.

In plant immunity, recognition of pathogen effectors by plant resistance proteins leads to the activation of plant defenses and a localized cell death response. The AvrM effector from flax rust is a small secreted protein that is recognized by the M resistance protein in flax. Here, we investigate the mechanism of M--AvrM recognition and show that these two proteins directly interact in a yeast two-hybrid assay, and that this interaction correlates with the recognition specificity observed for each of the different AvrM variants. We further characterize this interaction by demonstrating that the C-terminal domain of AvrM is required for M-dependent cell death, and show that this domain also interacts with the M protein in yeast. We investigate the role of C-terminal differences among the different AvrM proteins for their involvement in this interaction and establish that M recognition is hindered by an additional 34 amino acids present at the C terminus of several AvrM variants. Structural characterization of recombinant AvrM-A protein revealed a globular C-terminal domain that dimerizes.

© 2010 The American Phytopathological Society