The Nuclear Shuttle Protein ofTomato Leaf Curl New Delhi VirusIs a Pathogenicity Determinant

Abstract

Geminiviruses are single-stranded DNA viruses that infect a broad range of dicotyledonous and monocotyledonous plants. Viruses of the family Geminiviridae have been classified into four genera based on host range and genome organization (30). Of these, the whitefly-transmitted geminiviruses (genus Begomovirus) are the largest group, with more than 100 virus species identified so far (8). Geminiviruses replicate in the nuclei of host cells by a rolling-circle replication mechanism (reviewed in reference 11). For the propagation of infection in the host, these viruses encode movement proteins that direct the viral genome to the cortical cytoplasm and across the barrier of the cell wall. For bipartite begomoviruses, this process requires two proteins, encoded by the component designated DNA B: the nuclear shuttle protein (NSP) and the cell-to-cell movement protein (MP). These proteins act cooperatively to move the viral DNA from its site of replication in the nucleus to the cytoplasm and into adjacent plant cells (32).The geminivirus MP and NSP recognize DNA in a form-and size-specific manner (12,29). The NSP shuttles newly replicated viral DNA between the nucleus and the cytoplasm (42). MP traps these NSP-viral DNA complexes in the cytoplasm and redirects them to and across the plant cell wall (24,43). In adjacent cells, the NSP-viral DNA complexes are released, and NSP targets the viral DNA to the nucleus to initiate new rounds of infection. This process of movement is highly regulated. Recently, an acetyltransferase has been isolated from Arabidopsis thaliana that interacts with the NSP encoded by the bipartite begomovirus Cabbage leaf curl virus (22). This protein regulates the nuclear export of the viral DNA and is highly conserved in plants.

An unusual alphasatellite associated with monopartite begomoviruses attenuates symptoms and reduces betasatellite accumulation

“…The slower-growing strain LBA4404 that was transformed with pGSA-Alb4.3 or pGSA-Alb01and was cultured for 48 h with 3 mg ml -1 chloramphenicol. The test plants were agro-infiltrated, as described by Hussain et al (2005). The inoculation studies were conducted a minimum of three times.…”

The six Tomato yellow leaf curl virus genes expressed individually in tomato induce different levels of plant stress response attenuation

“…Little is known about the induction and inhibition of plant HR/CD by the different geminivirus gene products. For the bipartite begomoviruses, ToLCNDV and Bean dwarf mosaic virus, the elicitor of HR was shown to be NSP (GarridoRamirez et al 2000;Hussain et al 2005). ToLCNDV C1/Rep protein induced plant CD (Hussain et al 2005).…”

“…For the bipartite begomoviruses, ToLCNDV and Bean dwarf mosaic virus, the elicitor of HR was shown to be NSP (GarridoRamirez et al 2000;Hussain et al 2005). ToLCNDV C1/Rep protein induced plant CD (Hussain et al 2005). C1/Rep of two distinct begomoviruses, the bipartite African cassava mosaic virus (ACMV) and the monopartite Tomato yellow leaf curl China virus (TYLCCNV), elicited a reaction resembling HR, when expressed from a PVX vector in N. benthamiana (van Wezel et al 2002).…”

“…However, the nuclear shuttle protein (NSP) encoded by the bipartite begomovirus ToLCNDV DNA B-induced CD when expressed under the control of the Cauliflower mosaic virus (CaMV) 35S promoter or when cloned in a Potato virus X (PVX) expression vector (Hussain et al 2005). These results suggested that ToLCNDV-encoded protein(s) counteracted the NSP-dependent HR/CD responses.…”

“…These results suggested that ToLCNDV-encoded protein(s) counteracted the NSP-dependent HR/CD responses. Analysis of the ToLCNDV-encoded genes pointed to the transcriptional activator protein (TrAP) (encoded by DNA A) as the factor mediating the anti-HR effect (Hussain et al 2005). Later on, the V2 protein of two monopartite begomoviruses, Papaya leaf curl virus (PaLCuV) and Cotton leaf curl Kokhran virus (CLCuKoV), was shown to be a pathogenicity determinant and a target of host defense responses in N. benthamiana and N. tabacum plants (Mubin et al 2010).…”