A putative serine protease, SpSsp1, from Saprolegnia parasitica is recognised by sera of rainbow trout, Oncorhynchus mykiss

Acknowledgements Our work was supported by the BBSRC (BB/C518457/1, BB/G012075/1, BB/J018333/1) (K.L.M., C.J.S., J.S.C., K.S.D., and P.v.W.), the University of Aberdeen (V.L.A., C.J.S., and P.v.W.), MSD Animal Health (J.S.C., K.S.D., and A.H.v.d.B), and The Royal Society (P.v.W.). This work was also supported by a Marie Curie Initial Training Networks with the SAPRO (sustainable approaches to reduce Oomycete (Saprolegnia) infections in aquacultures) grant PITN-GA-2009-238550 (A.H.v.d.B., L.L., C.J.S., P.v.W.). We would like to acknowledge Aberdeen Proteomics for carrying out LC–MS/MS and Laura Grenville-Briggs for valuable discussion and technical help. We are grateful to the Broad Institute (Carsten Russ, Rays Jiang, Brian Haas, and Chad Nusbaum), Brett Tyler (VBI), and P.v.W. for early release of draft supercontigs of the genome sequence of isolate CBS233.65, which helped us identify SpSsp1.Peer reviewedPublisher PD

Host-targeting protein 1 (SpHtp1) from the oomycete Saprolegnia parasitica translocates specifically into fish cells in a tyrosine-O-sulphate-dependent manner

The eukaryotic oomycetes, or water molds, contain several species that are devastating pathogens of plants and animals. During infection, oomycetes translocate effector proteins into host cells, where they interfere with host-defense responses. For several oomycete effectors (i.e., the RxLR-effectors) it has been shown that their N-terminal polypeptides are important for the delivery into the host. Here we demonstrate that the putative RxLR-like effector, host-targeting protein 1 (SpHtp1), from the fish pathogen Saprolegnia parasitica translocates specifically inside host cells. We further demonstrate that cell-surface binding and uptake of this effector protein is mediated by an interaction with tyrosine-O-sulfate–modified cell-surface molecules and not via phospholipids, as has been reported for RxLR-effectors from plant pathogenic oomycetes. These results reveal an effector translocation route based on tyrosine-O-sulfate binding, which could be highly relevant for a wide range of host–microbe interactions