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Resistance Mutation Conserved Between Insects and Mites Unravels the Benzoylurea Insecticide Mode of Action on Chitin Biosynthesis

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Resistance Mutation Conserved Between Insects and Mites Unravels the Benzoylurea Insecticide Mode of Action on Chitin Biosynthesis Resistance mutation conserved between insects and mites unravels the benzoylurea insecticide mode of action on chitin biosynthesis Vassilis Dourisa,b,1, Denise Steinbachc,d,1, Rafaela Panteleria,b, Ioannis Livadarasa, John Anthony Pickette,2, Thomas Van Leeuwenf,g, Ralf Nauenc,2, and John Vontasa,h,2 aInstitute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas, GR-70013 Heraklion, Crete, Greece; bLaboratory of Molecular Entomology, Department of Biology, University of Crete, GR-70013 Heraklion, Crete, Greece; cBayer CropScience AG, R&D Pest Control Biology, D-40789 Mannheim, Germany; dDevelopmental Biology, Department of Biology, Martin-Luther University Halle-Wittenberg, 06120 Halle, Germany; eDepartment of Biological Chemistry and Crop Protection, Rothamsted Research, Hertfordshire, Harpenden AL5 2JQ, United Kingdom; fInstitute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, 1098 XH Amsterdam, The Netherlands; gLaboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, 9000 Ghent, Belgium; and hLaboratory of Pesticide Science, Department of Crop Science, Agricultural University of Athens, GR-11855 Athens, Greece Contributed by John Anthony Pickett, November 7, 2016 (sent for review July 26, 2016; reviewed by Simon W. Baxter, John E. Casida, Richard ffrench- Constant, and Charles S. Wondji) Despite the major role of chitin biosynthesis inhibitors such as current insecticides have neurotoxic and muscle action (>80%), benzoylureas (BPUs) in the control of pests in agricultural and whereas only a relatively small proportion interfere with growth and public health for almost four decades, their molecular mode of development (insect growth regulators, IGRs) and thus are highly action (MoA) has in most cases remained elusive. BPUs interfere selective to targeted arthropod pests as there are often no physio- with chitin biosynthesis and were thought to interact with logically related processes or target sites present in vertebrates. IGRs sulfonylurea receptors that mediate chitin vesicle transport. Here, are a group of chemically diverse compounds including the micro- we uncover a mutation (I1042M) in the chitin synthase 1 (CHS1) bial-derived pyrimidine-nucleoside peptides, benzoylureas (BPUs), SCIENCES gene of BPU-resistant Plutella xylostella at the same position as oxazolines, and thiadiazines (6) that all interfere with chitin bio- the I1017F mutation reported in spider mites that confers etoxa- synthesis or transport and deposition pathways. The MoA of the APPLIED BIOLOGICAL zole resistance. Using a genome-editing CRISPR/Cas9 approach antifungal pyrimidine-nucleoside antibiotics is by their function as coupled with homology-directed repair (HDR) in Drosophila mela- substrate analogs of UDP-N-acetylglucosamine at the catalytic site of nogaster, we introduced both substitutions (I1056M/F) in the cor- chitin synthase (CHS) and are thus considered competitive inhibitors responding fly CHS1 gene (kkv). Homozygous lines bearing either – of these mutations were highly resistant to etoxazole and all (7 9). BPUs (10), such as the major mosquito larvicide diflu- tested BPUs, as well as buprofezin—an important hemipteran chi- benzuron and the agriculturally widely used insecticides triflumuron tin biosynthesis inhibitor. This provides compelling evidence that and lufenuron, represent a group of compounds (group 15 with BPUs, etoxazole, and buprofezin share in fact the same molecular regard to the IRAC grouping system; see also Fig. S1)thatinhibit MoA and directly interact with CHS. This finding has immediate chitin biosynthesis by a unique yet elusive mechanism of action in- effects on resistance management strategies of major agricultural dependent of the catalytic reaction of CHS itself (6, 10, 11). Al- pests but also on mosquito vectors of serious human diseases such though the sulfonylurea receptor (SUR) has been suggested as the as Dengue and Zika, as diflubenzuron, the standard BPU, is one of the few effective larvicides in use. The study elaborates on how Significance genome editing can directly, rapidly, and convincingly elucidate the MoA of bioactive molecules, especially when target sites are An old enigma in insect toxicology, the mode of action (MoA) of complex and hard to reconstitute in vitro. selective chitin biosynthesis inhibitors in arthropods, is resolved. Benzoylureas, buprofezin, and etoxazole share a MoA by di- insecticide resistance | benzoylureas | CRISPR/Cas9 | resistance rectly interacting with chitin synthase 1. The finding that a single management | mosquito control mutation confers striking levels of insecticide resistance against three putative different MoAs has important ramifications on nsects pose tremendous threats to humans in two main areas. resistance management strategies and rational use of insecti- IPathogens causing diseases such as malaria, dengue fever, and cides against major agricultural pests and vectors of human more recent problems caused by the Zika virus, are vectored by diseases. Our results also show that CRISPR/Cas9-mediated gain- mosquitos, such as the Anopheles gambiae and Aedes aegypti, and of-function mutations in single-copy genes of highly conserved cause severe global health problems (1). Furthermore, the sus- target sites in arthropods provide opportunities for compre- tainability of agricultural yields, which need to meet predicted hensive insecticide resistance investigations across species population growth (2), is seriously threatened by pest insects and boundaries and against several insecticide classes. mites. The diamondback moth Plutella xylostella, a global lepi- dopterous pest of brassicaceous vegetables, is one of the economi- Author contributions: V.D., D.S., T.V.L., R.N., and J.V. designed research; V.D., D.S., R.P., and I.L. cally most important agricultural pests in the world, particularly due performed research; V.D., R.P., and I.L. performed CRISPR/Cas9 experiments in Drosophila;D.S. performed experiments in Plutella xylostella; V.D., D.S., J.A.P., T.V.L., R.N., and J.V. analyzed to it having developed resistance to almost all chemical classes of data; and V.D., D.S., J.A.P., R.N., and J.V. wrote the paper. insecticides applied for its control under continuous insecticide Reviewers: S.W.B., University of Adelaide; J.E.C., University of California, Berkeley; R.f.-C, pressure (3). University of Exeter; and C.S.W., Liverpool School of Tropical Medicine. Protection of food sources and human health from invertebrate The authors declare no conflict of interest. pests is critically reliant on insecticides (4, 5). Insecticides are clas- 1V.D. and D.S. contributed equally to this work. sified according to mode of action (MoA) and chemistry into several 2To whom correspondence may be addressed. Email: [email protected], groups through the IRAC (Insecticide Resistance Action Commit- [email protected], or [email protected]. tee) insecticide grouping system, which is the basis for their rational This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. use and resistance management strategies (4). The vast majority of 1073/pnas.1618258113/-/DCSupplemental. www.pnas.org/cgi/doi/10.1073/pnas.1618258113 PNAS Early Edition | 1of6 Downloaded by guest on October 4, 2021 direct target of BPUs (12) by affecting chitin biosynthesis indirectly generations resulted in high BPU cross-resistance compared with by altering vesicle trafficking, its role in chitin biosynthesis inhibition the parental strain and reference strains BCS-S and Japan (Table remains controversial (13, 14). Furthermore, it was recently shown 1). The selected strain Sudlon-Tfm was not only resistant to that SUR is dispensable for cuticle formation and chitin biosynthesis chemically diverse BPUs but also etoxazole (>178-fold), a chitin in Drosophila melanogaster (15). biosynthesis inhibitor of a different chemical class. Reciprocal Buprofezin (group 16) and etoxazole (group 10B) are two crosses between Sudlon-Tmf and BCS and Sudlon revealed that other, chemically different compounds (Fig. S1) highly selective the resistance was inherited autosomal recessive (Fig. 1) with a to sucking agricultural pests that have also been proposed to degree of dominance ranging from –0.73 to –0.88 in all re- interfere with chitin biosynthesis or cuticle formation (16, 17). ciprocal crosses (Table S1). Comparison of the postembryonic Etoxazole is an oxazoline acaricide widely used against pest mite developmental time of strains Sudlon and Sudlon-Tfm showed species but with limited activity on insects (18). Genomic map- that Sudlon-Tfm had a significantly longer larval (fourth instar) ping of a recessive monogenic etoxazole resistance locus in the and pupal development time (Fig. S2), which could be indicative two-spotted spider mite Tetranychus urticae, together with addi- of possible fitness costs associated with the selected BPU re- tional genetic and biochemical evidence, suggests that a single sistance trait in Plutella. mutation in CHS1 is associated with etoxazole resistance; this Based on (i) the identical symptoms of poisoning observed mutation, I1017F (T. urticae numbering), is located in the following exposure to both BPUs and etoxazole, (ii) the in- C-terminal transmembrane domain. Therefore, it is likely that heritance of resistance in an autosomal and recessive way in line CHS1 is the molecular target of etoxazole as well as the chem- to the etoxazole resistance
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