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Ptr ToxA Interacts with a Chloroplast-Localized Protein

February 2007 , Volume 20 , Number  2
Pages  168 - 177

Viola A. Manning , Linda K. Hardison , and Lynda M. Ciuffetti

Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331, U.S.A.

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Accepted 4 September 2006.

Pyrenophora tritici-repentis, causal agent of tan spot of wheat, produces host-selective toxins that are determinants of pathogenicity or virulence. Ptr ToxA (ToxA), a proteina-ceous toxin produced by P. tritici-repentis, is a necrotizing toxin produced by the most common races isolated from infected wheat. Recent studies have shown that ToxA is internalized into the mesophyll cells and localizes to chloroplasts of sensitive wheat cultivars only. We employed a yeast two-hybrid screen in an effort to determine plant proteins that interact with ToxA and found that ToxA interacts with a chloroplast protein, designated ToxA binding protein 1 (ToxABP1). ToxABP1 contains a lysine-rich region within a coiled-coil domain that is similar to phosphotidyl-inositol binding sites present in animal proteins involved in endocytosis. In both ToxA-sensitive and -insensitive cultivars, ToxABP1 is expressed at similar levels and encodes an identical protein. ToxABP1 protein is present in both chloroplast membranes and chloroplast stroma. ToxA appears to interact primarily with a multimeric complex of ToxABP1 protein associated with the chloroplast membrane.

Additional keywords: integrin, Psb29, RGD cell-attachment motif, thylakoid formation1.

© 2007 The American Phytopathological Society