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Tobacco Transcription Factor WRKY1 Is Phosphorylated by the MAP Kinase SIPK and Mediates HR-Like Cell Death in Tobacco

October 2005 , Volume 18 , Number  10
Pages  1,027 - 1,034

Frank L. H. Menke , 1 Hong-Gu Kang , 1 Zhixiang Chen , 2 Jeong Mee Park , 1 Dhirendra Kumar , 1 and Daniel F. Klessig 1

1Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853, U.S.A.; and 2Department of Botany and Plant Pathology, Purdue University, 915 West State Street, West Lafayette, IN 47907, U.S.A.

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Accepted 16 June 2005.

The salicylic acid-induced protein kinase (SIPK) of tobacco, which is a mitogen-activated protein kinase (MAPK), is activated by various biotic and abiotic treatments. Overexpression of SIPK has been shown to trigger cell death. In this study, a targeted yeast two-hybrid approach identified the tobacco transcription factor WRKY1 as a potential substrate. SIPK phosphorylated WRKY1, which resulted in enhanced DNA-binding activity of WRKY1 to its cognate binding site, a W box sequence from the tobacco chitinase gene CHN50. SIPK-mediated enhancement of WRKY1 DNA-binding activity was inhibited by staurosporine, a general kinase inhibitor. Co-expression of SIPK and WRKY1 in Nicotiana benthamiana led to more rapid cell death than expression of SIPK alone, suggesting that WRKY1 is involved in the formation of hypersensitive response-like cell death and may be a component of the signaling cascade downstream of SIPK.

© 2005 The American Phytopathological Society