The mitogen-activated protein kinase kinase (MAPKK) tMEK2 from tomato (Solanum lycopersicum) is a key component in the defense pathways against pathogen attacks. Because tMEK2-transgenic wheat (Triticum aestivum) has partial resistance to wheat leaf rust (caused by Puccinia triticina), we studied tMEK2 functions in wheat by heterologous screening for tMEK2 interactive proteins in a wheat yeast two-hybrid library. Within the 46 positive colonies examined, four genes encoding tMEK2-interactive proteins were sequenced. One of them was wheat GS1b, a cytosolic glutamine synthetase (GS). Its interaction with tMEK2 was confirmed by cotransformation in yeast (Saccharomyces cerevisiae) and by coimmunoprecipitation. The GS activities remained higher in tMEK2 transgenic wheat than in wild-type control during fungal toxin treatment. Our results provide evidence that tMEK2 plays multiple roles in plant defense against pathogen attacks, not only by activating downstream MAPKs and pathogenesis-related proteins but also possibly by recruiting metabolic pathways.

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Canadian Journal of Plant Pathology
Department of Biology

Fan, T. (T.), Gao, Y. (Y.), Al-Shammari, A. (A.), Wang, X.J. (X. J.), & Xing, T. (2009). Yeast two-hybrid screening of MAP kinase cascade identifies cytosolic glutamine synthetase 1b as a tMEK2 interactive protein in wheat. Canadian Journal of Plant Pathology, 31(4), 407–414. doi:10.1080/07060660909507615