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The Hypersensitive Response to Tomato leaf curl New Delhi virus Nuclear Shuttle Protein Is Inhibited by Transcriptional Activator Protein

December 2007 , Volume 20 , Number  12
Pages  1,581 - 1,588

Mazhar Hussain, Shahid Mansoor, Shazia Iram, Yusuf Zafar, and Rob W. Briddon

National Institute for Biotechnology and Genetic Engineering, Jhang Road, Faisalabad, Pakistan

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Accepted 11 July 2007.

The hypersensitive response (HR) is a common feature of plant disease resistance reactions and a type of programmed cell death (PCD). Many pathogens are able to modulate pathways involved in cell death. In contrast to animal viruses, inhibitors of PCD activity have not been identified for plant-infecting viruses. Previously, we have reported that the nuclear shuttle protein (NSP) of Tomato leaf curl New Delhi virus (ToLCNDV) induces an HR in Nicotiana tabacum and Lycopersicon esculentum plants when expressed under the control of the Cauliflower mosaic virus 35S promoter. However, HR is not evident in plants infected with ToLCNDV, suggesting that the virus encodes a factor (or factors) that counters this response. Analysis of all ToLCNDV-encoded genes pinpointed the transcriptional activator protein (TrAP) as the factor mediating the anti-HR effect. Deletion mutagenesis showed the central region of TrAP, containing a zinc finger domain and nuclear localization signal, to be important in inhibiting the HR. These results demonstrate that TrAP counters HR-induced cell death, the first such activity identified for a plant-infecting virus.

© 2007 The American Phytopathological Society