Yan Meng1 and
Roger P. Wise1,2
1Department of Plant Pathology and Microbiology, Center for Plant Responses to Environmental Stresses, Iowa State University, Ames, IA 50011–1020, U.S.A.; 2Crop and Insect Genetics, Genomics, and Informatics Research Unit (CIGGIR), United States Department of Agriculture–Agricultural Research Service, Iowa State University
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Accepted 12 July 2012.
WRKY proteins represent a large family of transcription factors (TF), involved in plant development and defense. In all, 60 unique barley TF have been annotated that contain the WRKY domain; 26 of these are represented on the Barley1 GeneChip. Time-course expression profiles of these 26 HvWRKY TF were analyzed to investigate their role in mildew locus a (Mla)-mediated immunity to Blumeria graminis f. sp. hordei, causal agent of powdery mildew disease. Inoculation-responsive, Mla-specified interactions with B. graminis f. sp. hordei revealed that 12 HvWRKY were differentially expressed: 10 highly upregulated and two significantly downregulated. Barley stripe mosaic virus-induced gene silencing of HvWRKY10, HvWRKY19, and HvWRKY28 compromised resistance-gene-mediated defense to powdery mildew in genotypes harboring both Rar1-dependent and Rar1-independent Mla alleles, indicating that these WRKY TF play key roles in effector-triggered immunity. Comprehensive yeast two-hybrid analyses, however, did not reveal a direct interaction between these three nuclear-localized WRKY TF and MLA. Transient overexpression of all three WRKY TF in single cells expressing Mlo, which encodes a negative regulator of penetration resistance, significantly decreased susceptibility. Taken together, these loss- and gain-of-function studies demonstrate that HvWRKY10, HvWRKY19, and HvWRKY28 positively regulate the barley transcriptome in response to invasion by B. graminis f. sp. hordei.
This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 2012.