Lectin receptor kinases: potential immune receptors against Phytophthora pathogens

Phytophthora pathogens cause devastating diseases on a broad range of plant species. In this study we focus on legume-like (L-type) lectin receptor kinases (LecRKs), a sub class of receptor-like kinases that could be employed as novel types of immune receptors to control Phytophthora pathogens. Previously, we found that Arabidopsis LecRK-I.9 functions as a Phytophthora resistance component (Bouwmeester et al., 2011, PLoS Pathogens). LecRK-I.9 belongs to a family consisting of 45 members in Arabidopsis. The function of other LecRKs was determined by infection assays on Arabidopsis T-DNA insertion mutants with various Phytophthora spp. as well as the bacterial pathogen Pseudomonas syringae and the fungal pathogen Alternaria brassicicola. Several of the LecRKs were found to play a role in resistance to Phytophthora but not to other pathogens. Overexpression of one of these, here named LecRK-a, enhanced Phytophthora disease resistance and also induced cell death in Arabidopsis. However, further analysis of the functional domains and 44 downstream signaling components indicated that the LecRK-a mediated Phytophthora resistance is independent of the cell death phenotype. Mass spectrometry of proteins that are in a complex with LecRK-a upon co-immunoprecipitation led to the identification of LIP1, a so-called LecRK-a-Interacting-Protein-1, which was confirmed to interact with LecRK-a in planta. Similar to lecrk-a lines, LIP1 T-DNA insertion mutants showed compromised Phytophthora disease resistance. Further analysis on the interaction between LecRK-a and LIP1 will provide a better insight into how LecRK-a mediates resistance to Phytophthora pathogens