A structural homologue of the plant receptor D14 mediates responses to strigolactones in the fungal phytopathogen Cryphonectria parasitica

• Strigolactones (SLs) are plant hormones and important signaling molecules required to promote the arbuscular mycorrhizal (AM) symbiosis. While in plants an alfa/beta hydrolase, DWARF14 (D14), was shown to act as a receptor that binds and cleaves SLs, the fungal receptor for SLs is unknown. • Since AM fungi are currently not genetically tractable, in this study, we used the fungal pathogen Cryphonectria parasitica for which gene deletion protocols exist, as a model, as we have previously shown that it responds to SLs. By means of computational, biochemical and genetic analyses we identified a D14 structural homologue, CpD14. • Molecular homology modelling and docking support the prediction that CpD14 interacts with and hydrolyses SLs. The recombinant CpD14 protein shows / hydrolytic activity in vitro against the SLs synthetic analogue GR24; its enzymatic activity requires an intact Ser/His/Asp catalytic triad. CpD14 expression in the d14-1 loss-of-function Arabidopsis thaliana line did not rescue the plant mutant phenotype. However, gene inactivation by knock-out homologous recombination reduced fungal sensitivity to SLs. • These results indicate that CpD14 is involved in SLs responses in C. parasitica and strengthen the role of SLs as multifunctional molecules acting in plant microbe-interactions.