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HRT-Mediated Hypersensitive Response and Resistance to Turnip crinkle virus in Arabidopsis Does Not Require the Function of TIP, the Presumed Guardee Protein

October 2008 , Volume 21 , Number  10
Pages  1,316 - 1,324

Rae-Dong Jeong,1 A. C. Chandra-Shekara,1 Aardra Kachroo,1 Daniel F. Klessig,2 and Pradeep Kachroo1

1Department of Plant Pathology, University of Kentucky, Lexington, KY 40514, U.S.A.; 2Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 40053, U.S.A.

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Accepted 6 June 2008.

The Arabidopsis resistance protein HRT recognizes the Turnip crinkle virus (TCV) coat protein (CP) to induce a hypersensitive response (HR) in the resistant ecotype Di-17. The CP also interacts with a nuclear-targeted NAC family of host transcription factors, designated TIP (TCV-interacting protein). Because binding of CP to TIP prevents nuclear localization of TIP, it has been proposed that TIP serves as a guardee for HRT. Here, we have tested the requirement for TIP in HRT-mediated HR and resistance by analyzing plants carrying knockout mutation in the TIP gene. Our results show that loss of TIP does not alter HR or resistance to TCV. Furthermore, the mutation in TIP neither impaired the salicylic acid--mediated induction of HRT expression nor the enhanced resistance conferred by overexpression of HRT. Strikingly, the mutation in TIP resulted in increased replication of TCV and Cucumber mosaic virus, suggesting that TIP may play a role in basal resistance but is not required for HRT-mediated signaling.

Additional keywords:defense.

© 2008 The American Phytopathological Society