Grapevine fanleaf virus(GFLV)‐specific antibodies confer GFLV andArabis mosaic virus(ArMV) resistance inNicotiana benthamiana

SUMMARY Grapevine fanleaf virus (GFLV) is one of the most destructive pathogens of grapevine. In this study, we generated monoclonal antibodies binding specifically to the coat protein of GFLV. Antibody FL3, which bound most strongly to GFLV and showed cross-reactivity to Arabis mosaic virus (ArMV), was used to construct the single-chain antibody fragment scFvGFLVcp-55. To evaluate the potential of this single-chain variable fragment (scFv) to confer antibody-mediated virus resistance, transgenic Nicotiana benthamiana plants were generated in which the scFv accumulated in the cytosol. Recombinant protein levels of up to 0.1% total soluble protein were achieved. The T1 and T2 progenies conferred partial or complete protection against GFLV on challenge with the viral pathogen. The resistance to GFLV in transgenic plants was strictly related to scFvGFLVcp-55 accumulation levels, confirming that the antibody fragment was functional in planta and responsible for the GFLV resistance. In addition, transgenic plants conferring complete protection to GFLV showed substantially enhanced tolerance to ArMV. We demonstrate the first step towards the control of grapevine fanleaf degeneration, as scFvGFLVcp-55 could be an ideal candidate for mediating nepovirus resistance.