V3 protein encoded by mulberry crinkle leaf virus acts as a pathogenicity determinant in Nicotiana benthamiana

A potential pathogenicity determinant and its critical amino acid (aa) sequences of mulberry crinkle leaf virus (MCLV) were determined through expression of MCLV genes in Nicotiana benthamiana using a potato virus X (PVX) vector. Among six genes encoded by MCLV, expression of only V3 resulted in a severe downward-leaf-curling symptom in newly emerging leaves of N. benthamiana plants, which suggested that the V3 protein is a pathogenicity determinant of MCLV. Analyses of truncation mutations indicated that the 94 residues at the N terminus of V3 are sufficient to maintain the function of the pathogenicity determinant V3 in N. benthamiana.