Tandem Amplification of a Chromosomal Segment Harboring 5-Enolpyruvylshikimate-3-Phosphate Synthase Locus Confers Glyphosate Resistance in Kochia scoparia1[W][OPEN]

Genes encoding enolpyruvylshikimate phosphate synthase are tandemly arranged on chromosomes of field-evolved glyphosate-resistant Kochia scoparia . Recent rapid evolution and spread of resistance to the most extensively used herbicide, glyphosate, is a major threat to global crop production. Genetic...

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Published in:Plant physiology (Bethesda) 2014-07, Vol.166 (3), p.1200-1207
Main Authors: Jugulam, Mithila, Niehues, Kindsey, Godar, Amar S., Koo, Dal-Hoe, Danilova, Tatiana, Friebe, Bernd, Sehgal, Sunish, Varanasi, Vijay K., Wiersma, Andrew, Westra, Philip, Stahlman, Phillip W., Gill, Bikram S.
Format: Article
Language:English
Subjects:
s - Focus Issue
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Summary:Genes encoding enolpyruvylshikimate phosphate synthase are tandemly arranged on chromosomes of field-evolved glyphosate-resistant Kochia scoparia . 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.
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.114.242826