Speaker
Description
Biotrophic fungal plant pathogens co-evolve with their hosts often leading to narrow host ranges. New host specificities resulting in the emergence of novel plant diseases can arise after so-called host jumps. Resulting from a recent host jump, the biotrophic smut fungus Sporisorium reilianum exists in two distinct formae speciales, S. reilianum f.sp. reilianum (SRS) and S. reilianum f.sp. zeae (SRZ), causing head smut disease in sorghum or maize, respectively. On sorghum, SRZ causes the induction of a strong phytoalexin defense response precluding systemic fungal spread and preventing disease. In spite of genome sequence availability, the evolutionary events leading to host jump, host adaptation and host specificity in S. reilianum are still unknown. Using a combination of classical genetics, next-generation sequencing and gene deletion analysis we identified a nine-gene effector cluster tightly linked with host-specificity of SRS on sorghum. Each effector individually contributes to virulence and has an independent role in host adaptation. One effector supresses the phytoalexin defense response in Sorghum. The orthologous effector from SRZ cannot functionally complement its SRS ortholog. Instead, the SRZ effector leads to phytoalexins via effector-triggered immunity. This highlights the important evolutionary role of effectors in shaping host plant adaptation following a host jump.
