title: Population bulk segregant mapping uncovers resistance mutations and the mode of action of a chitin synthesis inhibitor in arthropods.
abstract: Because of its importance to the arthropod exoskeleton, chitin biogenesis is an attractive target for pest control. This point is demonstrated by the economically important benzoylurea compounds that are in wide use as highly specific agents to control insect populations. Nevertheless, the target sites of compounds that inhibit chitin biogenesis have remained elusive, likely preventing the full exploitation of the underlying mode of action in pest management. Here, we show that the acaricide etoxazole inhibits chitin biogenesis in Tetranychus urticae (the two-spotted spider mite), an economically important pest. We then developed a population-level bulk segregant mapping method, based on high-throughput genome sequencing, to identify a locus for monogenic, recessive resistance to etoxazole in a field-collected population. As supported by additional genetic studies, including sequencing across multiple resistant strains and genetic complementation tests, we associated a nonsynonymous mutation in the major T. urticae chitin synthase (CHS1) with resistance. The change is in a C-terminal transmembrane domain of CHS1 in a highly conserved region that may serve a noncatalytic but essential function. Our finding of a target-site resistance mutation in CHS1 shows that at least one highly specific chitin biosynthesis inhibitor acts directly to inhibit chitin synthase. Our work also raises the possibility that other chitin biogenesis inhibitors, such as the benzoylurea compounds, may also act by inhibition of chitin synthases. More generally, our genetic mapping approach should be powerful for high-resolution mapping of simple traits (resistance or otherwise) in arthropods.
authors.affiliation: Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, B-9000 Ghent, Belgium. thomas.vanleeuwen@ugent.be
authors.forename: Thomas
authors.initials: T
authors.lastname: Van Leeuwen
authors.forename: Peter
authors.initials: P
authors.lastname: Demaeght
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Osborne
authors.forename: Wannes
authors.initials: W
authors.lastname: Dermauw
authors.forename: Simon
authors.initials: S
authors.lastname: Gohlke
authors.forename: Ralf
authors.initials: R
authors.lastname: Nauen
authors.forename: Miodrag
authors.initials: M
authors.lastname: Grbic
authors.forename: Luc
authors.initials: L
authors.lastname: Tirry
authors.forename: Hans
authors.initials: H
authors.lastname: Merzendorfer
authors.forename: Richard M
authors.initials: RM
authors.lastname: Clark
mesh_terms: D000818:Animals; D001181:Arthropods / Q000502:physiology*; D002686:Chitin / Q000037:antagonists & inhibitors* / Q000737:chemistry; D002687:Chitin Synthase / Q000037:antagonists & inhibitors; D015925:Cryopreservation; D004132:Diflubenzuron / Q000737:chemistry; D004351:Drug Resistance; D005260:Female; D005656:Fungal Proteins / Q000378:metabolism; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D007306:Insecticides / Q000494:pharmacology; D008297:Male; D008954:Models, Biological; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010080:Oxazoles / Q000737:chemistry; D011157:Population Dynamics; D017434:Protein Structure, Tertiary; D014508:Urea / Q000737:chemistry
chemical_list: D005656:Fungal Proteins; D007306:Insecticides; D010080:Oxazoles; D002686:Chitin; D014508:Urea; D002687:Chitin Synthase; D004132:Diflubenzuron; C508136:etoxazole