title: The sterol-binding activity of PATHOGENESIS-RELATED PROTEIN 1 reveals the mode of action of an antimicrobial protein.
abstract: Pathogenesis-related proteins played a pioneering role 50 years ago in the discovery of plant innate immunity as a set of proteins that accumulated upon pathogen challenge. The most abundant of these proteins, PATHOGENESIS-RELATED 1 (PR-1) encodes a small antimicrobial protein that has become, as a marker of plant immune signaling, one of the most referred to plant proteins. The biochemical activity and mode of action of PR-1 proteins has remained elusive, however. Here, we provide genetic and biochemical evidence for the capacity of PR-1 proteins to bind sterols, and demonstrate that the inhibitory effect on pathogen growth is caused by the sequestration of sterol from pathogens. In support of our findings, sterol-auxotroph pathogens such as the oomycete Phytophthora are particularly sensitive to PR-1, whereas sterol-prototroph fungal pathogens become highly sensitive only when sterol biosynthesis is compromised. Our results are in line with previous findings showing that plants with enhanced PR-1 expression are particularly well protected against oomycete pathogens.
authors.affiliation: Department of Biology, University of Fribourg, Fribourg, Switzerland.
authors.forename: Jordi
authors.initials: J
authors.lastname: Gamir
authors.affiliation: Department of Biology, University of Fribourg, Fribourg, Switzerland.
authors.forename: Rabih
authors.initials: R
authors.lastname: Darwiche
authors.affiliation: Department of Biology, University of Fribourg, Fribourg, Switzerland.
authors.forename: Pieter
authors.initials: P
authors.lastname: Van't Hof
authors.affiliation: Department of Biology, University of Fribourg, Fribourg, Switzerland.
authors.forename: Vineet
authors.initials: V
authors.lastname: Choudhary
authors.affiliation: Department of Biology, University of Fribourg, Fribourg, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Stumpe
authors.affiliation: Department of Biology, University of Fribourg, Fribourg, Switzerland.
authors.forename: Roger
authors.initials: R
authors.lastname: Schneiter
authors.affiliation: Department of Biology, University of Fribourg, Fribourg, Switzerland.
authors.forename: Felix
authors.initials: F
authors.lastname: Mauch
mesh_terms: D000890:Anti-Infective Agents / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D060467:Disease Resistance / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions; D015151:Immunoblotting; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D010838:Phytophthora / Q000502:physiology; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D010944:Plants / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D011485:Protein Binding; D013261:Sterols / Q000378:metabolism*; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000382:microbiology
chemical_list: D000890:Anti-Infective Agents; D010940:Plant Proteins; D013261:Sterols; D002784:Cholesterol
keywords: CAP protein; PR-1; Phytophthora; antimicrobial protein; plant immunity; sterol binding