Tomato leaf curl Java']Java virus V2 protein is a determinant of virulence, hypersensitive response and suppression of posttranscriptional gene silencing

We previously identified the Tomato leaf curl Java virus-A (ToLCJV-A[ID]) from Southeast Asia as a new member of the emerging group of monopartite begomoviruses that require a betasatellite component for symptom induction. In this study, the role of V2 in viral pathogenesis and posttranscriptional gene silencing (PTGS) was studied. Our results showed V2 of ToLCJV-A[ID] elicits a reaction resembling the hypersensitive response (HR) associated with the induction of necrosis and a systemic burst of H2O2 production when expressed from a potato virus X vector in Nicotiana species and tomato. Transient expression of ToLCJV-A[ID] V2 after agroinfiltration of Nicotiana benthamiana and tomato also triggered HR-like cell death, demonstrating that ToLCJV-A[ID] V2 is a target of host defense responses. Deletion of 58 amino acids (aa) from the N-terminus did not affect the HR, suggesting that this region has no role in the HR, while deletion of 58 aa from the C-terminus of V2 abolished both the HR response and V2 silencing suppressor activity, suggesting that these sequences are required for the HR-like response and suppression of PTGS. This finding demonstrated that ToLCJV-A[ID] V2 is a pathogenicity determinant that elicits an HR-like response. (C) 2009 Elsevier Inc. All rights reserved.