Recombinant-antibody-mediated resistance against Tomato yellow leaf curl virus in Nicotiana benthamiana.

Tomato yellow leaf curl virus (TYLCV) is a geminivirus species whose members cause severe crop losses in the tropics and subtropics. We report the expression of a single-chain variable fragment (scFv) antibody that protected Nicotiana benthamiana plants from a prevalent Iranian isolate of the virus (TYLCV-Ir). Two recombinant antibodies (scFv-ScRep1 and scFv-ScRep2) interacting with the multifunctional replication initiator protein (Rep) were obtained from phage display libraries and expressed in plants, both as stand-alone proteins and as N-terminal GFP fusions. Initial results indicated that both scFvs and both fusions accumulated to a detectable level in the cytosol and nucleus of plant cells. Transgenic plants challenged with TYLCV-Ir showed that the scFv-ScRep1, but more so the fusion proteins, were able to suppress TYLCV-Ir replication. These results show that expression of a scFv-ScRep1-GFP fusion protein can attenuate viral DNA replication and prevent the development of disease symptoms. The present article describes the first successful application of a recombinant antibody-mediated resistance approach against a plant DNA virus.