Potato SOBIR1 and SOBIR1-like interact with the elicitin-response receptor (ELR) of potato and are involved in the response to INF1 elicitin of Phytophthora infestans

P715 - Late blight, caused by the oomycete Phytophthora infestans, is the most threatening disease of potato ( Solanum tuberosum, St). So far, plant breeding for late blight resistance was focused on the introduction of resistance (R) genes, which encode cytoplasmic receptors of the NB-LRR family. However, these introduced resistances have been defeated by the pathogen rather quickly. Currently, we are investigating whether immunity that is triggered upon perception of apoplastic pathogen elicitors can enhance late blight resistance. Previous work in our group led to the identification of ELR, a pattern recognition receptor (PRR) that recognizes several elicitins, a highly conserved family of secreted effectors of Phytophthora and Pythium spp. ELR encodes a receptor-like protein (RLP) and providesbroad spectrum recognition of various elicitins in potato. Since RLPs do not have a kinase domain, they were anticipated to require a co-regulatory receptor-like kinase (RLK) that does carry a kinase domain to initiate cytoplasmic signaling. Indeed, it was recently described that several RLPs form a constitutive complex with the RLK SOBIR1. Tostudy whether ELR associates withSOBIR1, we cloned several StSOBIR1 and StSOBIR1-like homologues from wild potato accessions. We found that these genes are highly conserved in Solanum spp. and co-immunoprecipitation experiments showed that all StSOBIR1 variants physically interact with ELR. Virus-induced gene silencing (VIGS) studies of the Nicotiana benthamiana SOBIR1 homologues resulted in a compromised response to INF1 of P. infestans in N. benthamiana. Together, our results suggest that StSOBIR1 and StSOBIR1-like are involved in the INF1 response by associating with ELR.