P-275 - Divergent Evolution and Functional Redundancy of NRC Variants Shape NRC Networks in Solanaceae

The NRC (NLR-required for cell death) family, acting as helper NLRs alongside diverse sensor NLRs, plays a crucial role in the immunity of solanaceous plants against pathogens. However, most research has focused on Solanum and Nicotiana species, leaving the evolutionary trajectories of NRC variants in other Solanaceae genera largely unexplored. In this study, we reconstructed the evolutionary history and conducted functional analyses of NRC variants identified from nine solanaceous species spanning different genera. Our findings reveal that NRC variants cluster into 11 subfamilies, with NRC2, NRC3, and NRC4 existing in most species examined, whereas other variants display presence/absence polymorphisms across species. Phylogenetic analyses indicate that the NRC family consists of two major groups with distinct evolutionary rates: NRC1/2/3 evolve more slowly, while NRC4/5/6/7/8/9 exhibit rapid divergent evolution. Cell death assays showed that NRC2/3/4 are partially redundant in mediating cell death. While NRC2/3/4 variants from the nine species are largely functionally interchangeable, subfunctionalization has occurred in certain lineages. Notably, NRC9, a relatively uncharacterized variant found exclusively in solanaceous genera outside Solanum, redundantly functions with NRC4 to induce cell death. Our findings uncover divergent evolutionary patterns among NRC variants and reveal how their functional dynamics shape the NRC network across solanaceous species.