title: Mandipropamid targets the cellulose synthase-like PiCesA3 to inhibit cell wall biosynthesis in the oomycete plant pathogen, Phytophthora infestans.
abstract: Oomycete plant pathogens cause a wide variety of economically and environmentally important plant diseases. Mandipropamid (MPD) is a carboxylic acid amide (CAA) effective against downy mildews, such as Plasmopara viticola on grapes and potato late blight caused by Phytophthora infestans. Historically, the identification of the mode of action of oomycete-specific control agents has been problematic. Here, we describe how a combination of biochemical and genetic techniques has been utilized to identify the molecular target of MPD in P. infestans. Phytophthora infestans germinating cysts treated with MPD produced swelling symptoms typical of cell wall synthesis inhibitors, and these effects were reversible after washing with H(2)O. Uptake studies with (14)C-labelled MPD showed that this oomycete control agent acts on the cell wall and does not enter the cell. Furthermore, (14)C glucose incorporation into cellulose was perturbed in the presence of MPD which, taken together, suggests that the inhibition of cellulose synthesis is the primary effect of MPD. Laboratory mutants, insensitive to MPD, were raised by ethyl methane sulphonate (EMS) mutagenesis, and gene sequence analysis of cellulose synthase genes in these mutants revealed two point mutations in the PiCesA3 gene, known to be involved in cellulose synthesis. Both mutations in the PiCesA3 gene result in a change to the same amino acid (glycine-1105) in the protein. The transformation and expression of a mutated PiCesA3 allele was carried out in a sensitive wild-type isolate to demonstrate that the mutations in PiCesA3 were responsible for the MPD insensitivity phenotype.
authors.affiliation: Syngenta Crop Protection AG, CH-4332 Stein, Switzerland.
authors.forename: Mathias
authors.initials: M
authors.lastname: Blum
authors.forename: Martine
authors.initials: M
authors.lastname: Boehler
authors.forename: Eva
authors.initials: E
authors.lastname: Randall
authors.forename: Vanessa
authors.initials: V
authors.lastname: Young
authors.forename: Michael
authors.initials: M
authors.lastname: Csukai
authors.forename: Sabrina
authors.initials: S
authors.lastname: Kraus
authors.forename: Florence
authors.initials: F
authors.lastname: Moulin
authors.forename: Gabriel
authors.initials: G
authors.lastname: Scalliet
authors.forename: Anna O
authors.initials: AO
authors.lastname: Avrova
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Whisson
authors.forename: Raymonde
authors.initials: R
authors.lastname: Fonne-Pfister
mesh_terms: D020418:Algal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000577:Amides / Q000494:pharmacology*; D000595:Amino Acid Sequence; D002264:Carboxylic Acids / Q000494:pharmacology*; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism*; D002482:Cellulose / Q000096:biosynthesis; D003433:Crosses, Genetic; D005020:Ethyl Methanesulfonate; D018628:Gene Dosage / Q000235:genetics; D005947:Glucose / Q000378:metabolism; D005964:Glucosyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016296:Mutagenesis / Q000187:drug effects; D009154:Mutation / Q000235:genetics; D055750:Phytophthora infestans / Q000166:cytology / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D010944:Plants / Q000187:drug effects / Q000382:microbiology*; D014170:Transformation, Genetic / Q000187:drug effects
chemical_list: D020418:Algal Proteins; D000577:Amides; D002264:Carboxylic Acids; C550943:mandipropamid; D002482:Cellulose; D005020:Ethyl Methanesulfonate; D005964:Glucosyltransferases; C478648:cellulose synthase; D005947:Glucose
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