Two atypical resistance proteins confer plant resistance to Melanaphis sorghi in sorghum

burst and enhanced callose deposition. Accordingly, silencing of MsEF1 expression by RNA interference disrupted RMES1A/RMES1B-mediated resistance, as evidenced by significantly greater growth and fecundity of MES aphids on a resistant cultivar. Structural modeling predicted that RMES1A/RMES1B possess a potential nucleotide-binding domain and two leucine-rich repeat domains but lack the coiled-coil or Toll/interleukin-1 receptor/resistance domains observed in typical nucleotide-binding leucine-rich repeat immune receptors (NLRs). Moreover, RMES1A/RMES1B and their homologs form a distinct cluster in a phylogenetic tree of plant NLRs and likely represent a new type of plant NLR. Our work thus reveals new resistance genes that can be used to investigate and improve immunity against insect pests in sorghum and other crops.