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Members of the Arabidopsis WRKY Group III Transcription Factors Are Part of Different Plant Defense Signaling Pathways

April 2003 , Volume 16 , Number  4
Pages  295 - 305

Monika Kalde , Meike Barth , Imre E. Somssich , and Bernadette Lippok

Max-Planck-Institut für Züchtungsforschung, Abteilung Molekulare Phytopathologie, Carl-von-Linné Weg 10, D-50829 Köln, Germany

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Accepted 11 December 2002.

WRKY proteins are a large group of transcription factors restricted to the plant kingdom. In Arabidopsis thaliana, the gene family consists of 74 members. Here, we analyzed the expression of all 13 members of one main WRKY subgroup and found that the majority are responsive both to pathogen infection and to salicylic acid. Temporal expression studies during compatible, incompatible, and nonhost interactions and employing plant defense-signaling mutants allowed us to define four distinct WRKY subsets responding to different signaling queues along defense pathways. These subsets did not reflect phylogenetic relationships. Promoter studies of one member, AtWRKY54, using a reporter gene construct in transgenic Arabidopsis plants, revealed that regulatory regions mediating pathogen and SA inducibility are clearly separable. In an AtWRKY54 knockout line, resistance to Peronospora parasitica was not compromised, but the transient expression kinetics of several WRKY genes was affected, suggesting both the existence of functional redundancy and intense cross-talk between signaling networks.

Additional keywords: ascomycete Blumeria graminis, nahG, oomycete, pad4, RPP2, RPP4.

© 2003 The American Phytopathological Society