Phytophthora capsici-Arabidopsis, a model pathosystem for studying the role of lectin receptor kinases in Phytophthora disease resistance

The oomycete pathogen Phytophthora capsici is able to infect a wide range of plants and causes extensive losses in Solanum and Cucurbita crop plants. To better understand the interactions between P. capsici and its host plants, information gained from model pathosystems will be instrumental. Here, we describe a novel pathosystem between P. capsici and Arabidopsis. We screened a large collection of Arabidopsis accessions with several isolates of P. capsici, and found interaction specificity among isolateaccession combinations. In compatible interactions, appressorium-mediated penetration was followed by formation of invasive hyphae, haustoria and sporulation on leaves and roots. In contrast, in incompatible interactions, Arabidopsis activated defense responses including callose deposition, strong accumulation of H2O2 and O2- and cell death resulting in early pathogen encasement. Defense-related genes involved in camaelxin and indole-glucosinolate pathways were strongly induced upon infection by P. capsici. Moreover, mutants impaired in these pathways showed compromised resistance to P. capsici. Previously, an Arabidopsis legume-like lectin receptor kinase (LecRK), LecRK-I.9, was identified to be essential for Phytophthora resistance. LecRK-I.9 is a member of a family consisting of 45 genes. How other family members contribute to oomycete disease resistance is not yet known. The Phytophthora capsici- Arabidopsis pathosystem will be used for functional characterization of LecRK genes.