Evolution of NLR resistance genes with non-canonical N-terminal domains in wild tomato species

Background Nucleotide-binding and leucine-rich repeat immune receptors (NLRs) are an important component of plant immunity that provides resistance against diverse pathogens. NLRs often exist as large gene families, the members of which display diverse multi-domain architectures (MDAs) and evolve through various mechanisms of duplications and selections. Results We conducted resistance gene enrichment sequencing (RenSeq) with single-molecule real time (SMRT) sequencing of PacBio for 18 accessions in Solanaceae including 15 wild tomatoes. We demonstrate what was previously known as Solanaceae Domain (SD) not only is more diverse in structure and function but also far anciently originated from the most recent common ancestor (MRCA) between Asterids and Amaranthaceae. In tomato, NLRs with the extended N-terminus displayed distinct patterns of evolution based on phylogenetic clades by proliferation, continuous elongation and domain losses. Conclusions Our study provides high quality gene models of NLRs that can serve as resources for future studies for crop engineering and elucidates greater evolutionary dynamics of the extended NLRs than previously assumed.