Natural variation in insect egg-induced cell death uncovers a role for L-type LECTIN RECEPTOR KINASE-I.1 in Arabidopsis

In Arabidopsis thaliana, a hypersensitive-like response (HR-like) is triggered underneath the eggs of the large white butterfly Pieris brassicae, and this response is dependent on salicylic acid (SA) accumulation and signaling. Previous reports indicate that the clade I L-type lectin receptor kinase LecRK-I.8 is involved in early steps of egg recognition. A genome-wide association study (GWAS) was used to better characterize the genetic structure of HR-like and discover loci that contribute to this response. We report here the identification of LecRK-I.1, a close homolog of LecRK-I.8, and show that two main haplotypes that explain part of the variation in HR-like segregate amongst natural Arabidopsis accessions. In addition, signatures of balancing selection at this locus suggest that it may be ecologically important. Disruption of LecRK-I.1 resulted in decreased HR-like while SA-dependent signaling was unaffected, suggesting that this protein is specifically involved in the induction of cell death. Furthermore, we provide evidence that LecRK-I.1 functions in the same signaling pathway as LecRK-I.8. Altogether, our results show that the response to eggs of P. brassicae is controlled by LecRKs that operate at various steps of the signaling pathway.