Functional analysis of tomato responses to Verticillium dahliae

Verticillium dahliae is a soil-borne vascular pathogen of over 200 dicot plant species that include tomato. In our lab we have also established a successful soil-based V. dahliae-infection assay for Arabidopsis. Previously, from Verticillium-resistant tomato the so-called Ve locus was cloned that comprises two resistance gene analogs that encode receptor-like proteins (RLPs). RLPs are composed of extracellular leucine-rich repeats that are anchored in the plasmamembrane and only have a short cytoplasmic tail that lacks obvious signaling motifs. In our lab, we try to uncover the function of RLP-type disease resistance genes in Arabidopsis and tomato. In the Arabidopsis genome, 57 RLP-encoding genes (AtRLP genes) have been identified of which only CLV2 and TMM have previously been characterized. Both genes play a role in plant development through maintenance of stem cell populations and stomatal distribution, respectively. A knock-out collection for the 57 AtRLP genes was assembled and screened for altered susceptibility towards various microbial pathogens including Verticillium. In order to study defense signaling downstream of RLPs, we aim to unravel the signaling cascade that is activated by the Ve resistance proteins in tomato upon detection of Verticillium presence. Diverse candidate genes are assessed for their role in Ve-mediated resistance signaling. Furthermore, through diverse approaches we aim to characterize and study the effector catalogue of in planta-secreted Verticillium proteins. In this way, we not only hope to uncover virulence factors of Verticillium, but also expect to identify the Verticillium effector that is recognized by the Ve proteins.