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Enhancer Trapping Identifies TRI, an Arabidopsis Gene Up-Regulated by Pathogen Infection

October 2004 , Volume 17 , Number  10
Pages  1,086 - 1,094

Ingela Fridborg , 1 Alan Williams , 1 Aidong Yang , 1 Stuart MacFarlane , 2 Katherine Coutts , 1 and Susan Angell 1

1Department of Disease and Stress Biology, John Innes Centre, Norwich, NR4 7UH, U.K.; 2Scottish Crop Research Institute, Invergowie, Dundee, DD2 5DA, U.K.

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Accepted 3 June 2004.

Enhancer trap Arabidopsis thaliana plants were screened for genes up-regulated by virus infection. The plants carried T-DNA insertions comprising a minimal -60-bp Cauliflower mosaic virus 35S promoter fused to the β-glucuronidase (GUS) reporter gene. Approximately 12,000 plants were assayed for GUS activity before and after rub-inoculation with Tobacco rattle virus (TRV) tagged with the green fluorescent protein (GFP). One plant and its progeny consistently showed upregulation of GUS activity in response to TRV-GFP infection, indicating that a virus-responsive enhancer element was “tagged” by the T-DNA in this line. Other viruses, bacteria, and oomycetes, but not wounding, up-regulated GUS activity in the enhancer trap line, indicating that the response was not specific to TRV-GFP infection. A pathogen-inducible, alternatively spliced gene was identified, which we have termed TRI for TRV-induced gene. A pathogen-responsive element was localized to a 1.1-kb region upstream of the T-DNA insertion, and two different cis-acting elements, both implicated in defense responses, were found in the sequence upstream of TRI. Sequence analyses revealed that TRI is similar to ACRE169, a gene that is up-regulated in Cf-9-expressing tobacco when treated with Avr-9, the Cladosporium fulvum elicitor of the Cf-9 resistance response.

Additional keywords: gene regulation, WRKY transcription factor, W-box, as-1/ocs element.

© 2004 The American Phytopathological Society