title: Effect of Flumorph on F-Actin Dynamics in the Potato Late Blight Pathogen Phytophthora infestans.
abstract: Oomycetes are fungal-like pathogens that cause notorious diseases. Protecting crops against oomycetes requires regular spraying with chemicals, many with an unknown mode of action. In the 1990s, flumorph was identified as a novel crop protection agent. It was shown to inhibit the growth of oomycete pathogens including Phytophthora spp., presumably by targeting actin. We recently generated transgenic Phytophthora infestans strains that express Lifeact-enhanced green fluorescent protein (eGFP), which enabled us to monitor the actin cytoskeleton during hyphal growth. For analyzing effects of oomicides on the actin cytoskeleton in vivo, the P. infestans Lifeact-eGFP strain is an excellent tool. Here, we confirm that flumorph is an oomicide with growth inhibitory activity. Microscopic analyses showed that low flumorph concentrations provoked hyphal tip swellings accompanied by accumulation of actin plaques in the apex, a feature reminiscent of tips of nongrowing hyphae. At higher concentrations, swelling was more pronounced and accompanied by an increase in hyphal bursting events. However, in hyphae that remained intact, actin filaments were indistinguishable from those in nontreated, nongrowing hyphae. In contrast, in hyphae treated with the actin depolymerizing drug latrunculin B, no hyphal bursting was observed but the actin filaments were completely disrupted. This difference demonstrates that actin is not the primary target of flumorph.
authors.affiliation: First, second, fourth, and fifth authors: Laboratory of Phytopathology, and second and third authors: Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands; and fourth author: Centre for BioSystems Genomics, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Chenlei
authors.initials: C
authors.lastname: Hua
authors.forename: Kiki
authors.initials: K
authors.lastname: Kots
authors.forename: Tijs
authors.initials: T
authors.lastname: Ketelaar
authors.forename: Francine
authors.initials: F
authors.lastname: Govers
authors.forename: Harold J G
authors.initials: HJ
authors.lastname: Meijer
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D049452:Green Fluorescent Proteins; D025301:Hyphae; D009025:Morpholines / Q000494:pharmacology*; D055750:Phytophthora infestans / Q000166:cytology / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D010935:Plant Diseases / Q000382:microbiology*; D011198:Solanum tuberosum / Q000382:microbiology*; D053778:Thiazolidines / Q000494:pharmacology
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D009025:Morpholines; D053778:Thiazolidines; C485184:enhanced green fluorescent protein; C528737:flumorph; D049452:Green Fluorescent Proteins; C037068:latrunculin B
keywords: oomyceticide