title: Tandem amplification of a chromosomal segment harboring 5-enolpyruvylshikimate-3-phosphate synthase locus confers glyphosate resistance in Kochia scoparia.
abstract: Recent rapid evolution and spread of resistance to the most extensively used herbicide, glyphosate, is a major threat to global crop production. Genetic mechanisms by which weeds evolve resistance to herbicides largely determine the level of resistance and the rate of evolution of resistance. In a previous study, we determined that glyphosate resistance in Kochia scoparia is due to the amplification of the 5-Enolpyruvylshikimate-3-Phosphate Synthase (EPSPS) gene, the enzyme target of glyphosate. Here, we investigated the genomic organization of the amplified EPSPS copies using fluorescence in situ hybridization (FISH) and extended DNA fiber (Fiber FISH) on K. scoparia chromosomes. In both glyphosate-resistant K. scoparia populations tested (GR1 and GR2), FISH results displayed a single and prominent hybridization site of the EPSPS gene localized on the distal end of one pair of homologous metaphase chromosomes compared with a faint hybridization site in glyphosate-susceptible samples (GS1 and GS2). Fiber FISH displayed 10 copies of the EPSPS gene (approximately 5 kb) arranged in tandem configuration approximately 40 to 70 kb apart, with one copy in an inverted orientation in GR2. In agreement with FISH results, segregation of EPSPS copies followed single-locus inheritance in GR1 population. This is the first report of tandem target gene amplification conferring field-evolved herbicide resistance in weed populations.
authors.affiliation: Departments of Agronomy (M.J., K.N., A.S.G., V.K.V.) and Plant Pathology (D.-H.K., T.D., B.F., S.S., B.S.G.), Kansas State University, Manhattan, Kansas 66506;Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523 (A.W., P.W.); andKansas State University Agricultural Research Center, Hays, Kansas 67601 (P.W.S.) mithila@ksu.edu.
authors.forename: Mithila
authors.initials: M
authors.lastname: Jugulam
authors.affiliation: Departments of Agronomy (M.J., K.N., A.S.G., V.K.V.) and Plant Pathology (D.-H.K., T.D., B.F., S.S., B.S.G.), Kansas State University, Manhattan, Kansas 66506;Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523 (A.W., P.W.); andKansas State University Agricultural Research Center, Hays, Kansas 67601 (P.W.S.).
authors.forename: Kindsey
authors.initials: K
authors.lastname: Niehues
authors.affiliation: Departments of Agronomy (M.J., K.N., A.S.G., V.K.V.) and Plant Pathology (D.-H.K., T.D., B.F., S.S., B.S.G.), Kansas State University, Manhattan, Kansas 66506;Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523 (A.W., P.W.); andKansas State University Agricultural Research Center, Hays, Kansas 67601 (P.W.S.).
authors.forename: Amar S
authors.identifier: http://orcid.org/0000-0001-9980-6562
authors.initials: AS
authors.lastname: Godar
authors.affiliation: Departments of Agronomy (M.J., K.N., A.S.G., V.K.V.) and Plant Pathology (D.-H.K., T.D., B.F., S.S., B.S.G.), Kansas State University, Manhattan, Kansas 66506;Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523 (A.W., P.W.); andKansas State University Agricultural Research Center, Hays, Kansas 67601 (P.W.S.).
authors.forename: Dal-Hoe
authors.initials: DH
authors.lastname: Koo
authors.affiliation: Departments of Agronomy (M.J., K.N., A.S.G., V.K.V.) and Plant Pathology (D.-H.K., T.D., B.F., S.S., B.S.G.), Kansas State University, Manhattan, Kansas 66506;Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523 (A.W., P.W.); andKansas State University Agricultural Research Center, Hays, Kansas 67601 (P.W.S.).
authors.forename: Tatiana
authors.initials: T
authors.lastname: Danilova
authors.affiliation: Departments of Agronomy (M.J., K.N., A.S.G., V.K.V.) and Plant Pathology (D.-H.K., T.D., B.F., S.S., B.S.G.), Kansas State University, Manhattan, Kansas 66506;Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523 (A.W., P.W.); andKansas State University Agricultural Research Center, Hays, Kansas 67601 (P.W.S.).
authors.forename: Bernd
authors.initials: B
authors.lastname: Friebe
authors.affiliation: Departments of Agronomy (M.J., K.N., A.S.G., V.K.V.) and Plant Pathology (D.-H.K., T.D., B.F., S.S., B.S.G.), Kansas State University, Manhattan, Kansas 66506;Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523 (A.W., P.W.); andKansas State University Agricultural Research Center, Hays, Kansas 67601 (P.W.S.).
authors.forename: Sunish
authors.initials: S
authors.lastname: Sehgal
authors.affiliation: Departments of Agronomy (M.J., K.N., A.S.G., V.K.V.) and Plant Pathology (D.-H.K., T.D., B.F., S.S., B.S.G.), Kansas State University, Manhattan, Kansas 66506;Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523 (A.W., P.W.); andKansas State University Agricultural Research Center, Hays, Kansas 67601 (P.W.S.).
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Varanasi
authors.affiliation: Departments of Agronomy (M.J., K.N., A.S.G., V.K.V.) and Plant Pathology (D.-H.K., T.D., B.F., S.S., B.S.G.), Kansas State University, Manhattan, Kansas 66506;Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523 (A.W., P.W.); andKansas State University Agricultural Research Center, Hays, Kansas 67601 (P.W.S.).
authors.forename: Andrew
authors.initials: A
authors.lastname: Wiersma
authors.affiliation: Departments of Agronomy (M.J., K.N., A.S.G., V.K.V.) and Plant Pathology (D.-H.K., T.D., B.F., S.S., B.S.G.), Kansas State University, Manhattan, Kansas 66506;Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523 (A.W., P.W.); andKansas State University Agricultural Research Center, Hays, Kansas 67601 (P.W.S.).
authors.forename: Philip
authors.initials: P
authors.lastname: Westra
authors.affiliation: Departments of Agronomy (M.J., K.N., A.S.G., V.K.V.) and Plant Pathology (D.-H.K., T.D., B.F., S.S., B.S.G.), Kansas State University, Manhattan, Kansas 66506;Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523 (A.W., P.W.); andKansas State University Agricultural Research Center, Hays, Kansas 67601 (P.W.S.).
authors.forename: Phillip W
authors.initials: PW
authors.lastname: Stahlman
authors.affiliation: Departments of Agronomy (M.J., K.N., A.S.G., V.K.V.) and Plant Pathology (D.-H.K., T.D., B.F., S.S., B.S.G.), Kansas State University, Manhattan, Kansas 66506;Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523 (A.W., P.W.); andKansas State University Agricultural Research Center, Hays, Kansas 67601 (P.W.S.).
authors.forename: Bikram S
authors.initials: BS
authors.lastname: Gill
mesh_terms: D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase / Q000235:genetics* / Q000378:metabolism; D027467:Bassia scoparia / Q000201:enzymology* / Q000235:genetics; D005075:Biological Evolution; D002874:Chromosome Mapping; D005784:Gene Amplification; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D053209:Herbicide Resistance; D006540:Herbicides / Q000494:pharmacology*; D017404:In Situ Hybridization, Fluorescence; D008954:Models, Biological; D000097797:Glyphosate
chemical_list: D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase; D005998:Glycine; D006540:Herbicides; D000097797:Glyphosate