The Rice stripe virus pc4 functions in movement and foliar necrosis expression in Nicotiana benthamiana

The Rice stripe virus (RSV) pc4 has been determined as the viral movement protein (MP). In this study, the pc4 gene was cloned into a movement-deficient Tobacco mosaic virus (TMV). The resulting hybrid TMV-pc4, in addition to spreading cell to cell in Nicotiana tabacum, moved systemically and induced foliar necrosis in Nicotiana benthamiana, indicating novel functions of the RSV MP. A systematic alanine-scanning mutagenesis study established the region K122–D258 of the pc4 substantially associated with cell-to-cell movement, and mutants by replacement of KGR122–124, D135, ED170–171, ER201–202, EFE218–220 or ELD256–258 with alanine(s) no longer moved cell to cell. However, only one amino acid group KGR122–124 was linked with long-distance movement. The region D17–K33 was recognized as a crucial domain for leaf necrosis response, and mutagenesis of DD17–18 or RK32–33 greatly attenuated necrosis. The overall data suggested manifold roles of the pc4 during the RSV infection in its experimental host N. benthamiana.