The N gene protects tomato plants from tomato brown rugose fruit virus infection

The tobamovirus tomato brown rugose fruit virus (ToBRFV) has recently emerged, causing significant damage to the tomato industry in various regions worldwide, including the US. ToBRFV evades the widely used Tm-2² resistance gene, which encodes a nucleotide-binding leucine-rich repeat (NLR) class immune receptor with an N-terminal coiled-coil (CC) domain that confers resistance to the tomato mosaic virus (ToMV). In this study, we tested a transgenic tomato line (tomato^NN) expressing the Nicotiana glutinosa N gene, which encodes an NLR with a Toll-Interleukin 1 homology domain (TIR) at the N-terminus, for resistance to ToBRFV. Our results demonstrate that tomato^NN is resistant to ToBRFV, evidenced by the necrotic local lesions observed on the inoculated leaves and the absence of symptoms on systemic leaves. This correlates with very low to non-detectable virus levels in double antibody sandwich enzyme-linked immunosorbent (DAS-ELISA) and quantitative reverse transcription-polymerase chain reaction (RT-qPCR) assays. Furthermore, our findings reveal that tomato^NN is resistant to ToBRFV at 22 °C, but not at 30 °C, showing that the temperature-sensitive nature of N-mediated resistance also extends to ToBRFV resistance in tomato. These results highlight the significant potential of using tomato^NN to breed tomato cultivars resistant to ToBRFV, offering a new approach to managing the global pandemic caused by this emerging virus.