A butterfly egg-killing hypersensitive response in Brassica nigra is controlled by a single locus, PEK, containing a cluster of TIR-NBS-LRR receptors

The hypersensitive response (HR) characterizes monogenic qualitative resistance traits in several pathosystems. Knowledge on its role in plant resistance to insects is so far limited to a few resistance ( R ) gene-based resistances against piercing-sucking insects. Egg deposition by cabbage white butterflies ( Pieris spp.), pests of cabbage crops ( Brassica spp.), can trigger an HR-like cell death, which reduces egg survival and represents an effective plant resistance trait before feeding damage occurs. Here, we identified natural variation of HR-like to Pieris egg deposition in the black mustard ( B. nigra L.) and performed genetic mapping. HR-like segregated as a Mendelian trait and a single dominant locus on chromosome B3, named PEK ( P ieris e gg- k illing ) was identified. In the ~50 kb region, eleven candidate genes, are located, including a cluster of genes encoding intracellular receptor proteins, TIR-NBS-LRR (TNLs). The PEK locus was found to be highly polymorphic between the parental accessions of our mapping populations and among B. nigra reference genomes. Our study is the first that identifies a single locus potentially involved in HR-like cell death induced by insect eggs. Further fine-mapping, comparative genomics and validation of the PEK locus will shed light on the role of TNL receptors in egg-induced HR-like cell death.