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Expression of AtWRKY33 Encoding a Pathogen- or PAMP-Responsive WRKY Transcription Factor Is Regulated by a Composite DNA Motif Containing W Box Elements

April 2007 , Volume 20 , Number  4
Pages  420 - 429

Bernadette Lippok , 1 Rainer P. Birkenbihl , 1 Gaelle Rivory , 1 Janna Brümmer , 1 Elmon Schmelzer , 2 Elke Logemann , 1 and Imre E. Somssich 1

1Abteilung: Molekulare Phytopathologie and 2Abteilung: Zentrale Mikroskopie (CeMic), Max Planck Institut für Züchtungsforschung, Carl von Linné Weg 10, 50829 Köln, Germany

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Accepted 15 November 2006.

WRKY transcription factors regulate distinct parts of the plant defense transcriptome. Expression of many WRKY genes themselves is induced by pathogens or pathogen-mimicking molecules. Here, we demonstrate that Arabidopsis WRKY33 responds to various stimuli associated with plant defense as well as to different kinds of phytopathogens. Although rapid pathogen-induced AtWRKY33 expression does not require salicylic acid (SA) signaling, it is dependent on PAD4, a key regulator upstream of SA. Activation of AtWRKY33 is independent of de novo protein synthesis, suggesting that it is at least partly under negative regulatory control. We show that a set of three WRKY-specific cis-acting DNA elements (W boxes) within the AtWRKY33 promoter is required for efficient pathogen- or PAMP-triggered gene activation. This strongly indicates that WRKY transcription factors are major components of the regulatory machinery modulating immediate to early expression of this gene in response to pathogen attack.

Additional keywords: Alternaria, Hyaloperonospora parasitica, pathogen-associated molecular patterns.

© 2007 The American Phytopathological Society