A point mutation in the pepper veinal mottle virus 6K1 protein yields a stable attenuated strain for engineering virus resistance in pepper plants

A total of 164 viruses have been identified in peppers worldwide. To combat viruses, pathogen-derived resistance (PDR) has been employed by expressing a viral genomic segment or a viral protein in host plants. Unfortunately, peppers are recalcitrant to genetic transformation and regeneration. An alternative strategy is to generate PDR in pepper plants by using an attenuated virus-based expression vector. In a previous study on the function of pepper veinal mottle virus (PVMV) 6K1 protein, we mutated a conserved Ala with Arg (A15R), and a second mutation (R15G) was observed in virus progeny. In this study, we demonstrated that mutating Ala to Gly (A15G) in the 6K1 yields a stable attenuated strain (named PVMV-G-A15G). PVMV-G-A15G can cross-protect pepper plants against a severe strain of PVMV and its close relative, chilli veinal mottle virus. We then engineered PVMV-G-A15G into a viral expression vector that has the Golden Gate cloning feature. To examine if the PVMV vector can be used to mediate PDR, we inserted the complete CP sequence of potato virus X (PVX) into the engineered PVMV-G-A15G. Preinoculated plants with the recombinant PVMV-G-A15G that carries the PVX CP sequence are resistant to PVX infection. Taken together, our research demonstrates that the attenuated PVMV can be employed for delivering the target virus sequence to mediate PDR.