critical domain of Sweet potato chlorotic fleck virus nucleotide‐binding protein (NaBp) for RNA silencing suppression, nuclear localization and viral pathogenesis

• Published in: Molecular plant pathology Vol. 16; no. 4; pp. 365 - 375
• Main Authors: Deng, Xing‐Guang, Peng, Xing‐Ji, Zhu, Feng, Chen, Ying‐Juan, Zhu, Tong, Qin, Shao‐Bo, Xi, De‐Hui, Lin, Hong‐Hui
• Format: Journal Article
• Language: English
• Published: England Blackwell Science in collaboration with the British Society of Plant Pathology 01.05.2015; Blackwell Publishing Ltd; John Wiley & Sons, Inc; John Wiley and Sons Inc
• Subjects: Cell Nucleus - metabolism; confocal laser scanning microscopy; double-stranded RNA; green fluorescent protein; image analysis; Ipomoea batatas - virology; Mutation; NaBp; Nicotiana benthamiana; nuclear localization; nuclear localization signals; Original; Pathogenesis; pathogenicity; Pathogens; Plant Viruses - metabolism; Plant Viruses - pathogenicity; Potato virus X; Potatoes; Proteins; protoplasts; RNA Interference; RNA Viruses - metabolism; RNA Viruses - pathogenicity; sequence deletion; silencing suppressor; SPCFV; Sweet potato chlorotic fleck virus; viral pathogenesis; Viral Proteins - genetics; Viral Proteins - metabolism; Virulence; viruses; viral pathogenesis; nuclear localization; SPCFV; silencing suppressor; NaBp
• DOI: 10.1111/mpp.12186
• ISSN: 1464-6722

RNA silencing is an important mechanism of antiviral defence in plants. To counteract this resistance mechanism, many viruses have evolved RNA silencing suppressors. In this study, we analysed five proteins encoded by Sweet potato chlorotic fleck virus (SPCFV) for their abilities to suppress RNA silencing using a green fluorescent protein (GFP)‐based transient expression assay in Nicotiana benthamiana line 16c plants. Our results showed that a putative nucleotide‐binding protein (NaBp), but not other proteins encoded by the virus, could efficiently suppress local and systemic RNA silencing induced by either sense or double‐stranded RNA (dsRNA) molecules. Deletion mutation analysis of NaBp demonstrated that the basic motif (an arginine‐rich region) was critical for its RNA silencing suppression activity. Using confocal laser scanning microscopy imaging of transfected protoplasts expressing NaBp fused to GFP, we showed that NaBp accumulated predominantly in the nucleus. Mutational analysis of NaBp demonstrated that the basic motif represented part of the nuclear localization signal. In addition, we demonstrated that the basic motif in NaBp was a pathogenicity determinant in the Potato virus X (PVX) heterogeneous system. Overall, our results demonstrate that the basic motif of SPCFV NaBp plays a critical role in RNA silencing suppression, nuclear localization and viral pathogenesis.