Towards the identification of fungal effector molecules involved in host plant developmental reprogramming

P033 - Typically, Verticillium infections lead to severe wilting symptoms on their respective host plants with the remarkable exception of V. longisporum infected Brassicaceae, which maintain their water status. Recently, we could show that water status maintenance correlates with a substantial V. longisporum-induced developmental reprogramming on its host plants Brassica napus and Arabidopsis thaliana. Together, our data suggest that de novo formation of xylem by hyperplasia and transdifferentiation in response to infection by V. longisporum is likely to be a compensatory plant response resulting in increase of plant water storage capacity. We recently analyzed symptom development induced by 22 diploid V. longisporum and 43 haploid V. dahliae strains on Arabidopsis ecotype Col-0. Interestingly, we identified five V. dahliae strains that phenocopy the disease symptoms typically associated with V. longisporum infection. Notably, these isolates are also able to cause defoliation on their respective host plants cotton or olive. In contrast, we found several V. dahliae strains which induce strong wilting phenotypes and lateral branching, but lack the capacity to induce developmental reprogramming of vascular tissues. In accordance to that, two cotton non-defoliating isolates induced mild wilting symptoms but no chlorosis or de novo xylem formation on Arabidopsis. This indicates that fungal molecules involved in V. longisporum associated symptom development on Arabidopsis might be primarily prevalent in V. dahliae isolates causing defoliation on their respective host plants. Comparative genomic sequence analyses of these haploid V. dahliae strains will be conducted to identify and functionally characterize effector molecule candidates underlying the distinct infection symptoms.