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About the Authors:
Todd A. Gaines
* E-mail: [email protected]
Affiliations Australian Herbicide Resistance Initiative, School of Plant Biology, University of Western Australia, Crawley, Western Australia, Australia, Weed Resistance Research, Bayer CropScience, Frankfurt am Main, Germany
Alice A. Wright
Affiliation: Crop Production Systems Research Unit, United States Department of Agriculture - Agricultural Research Service, Stoneville, Mississippi, United States of America
William T. Molin
Affiliation: Crop Production Systems Research Unit, United States Department of Agriculture - Agricultural Research Service, Stoneville, Mississippi, United States of America
Lothar Lorentz
Affiliation: Weed Resistance Research, Bayer CropScience, Frankfurt am Main, Germany
Chance W. Riggins
Affiliation: Department of Crop Sciences, University of Illinois, Urbana, Illinois, United States of America
Patrick J. Tranel
Affiliation: Department of Crop Sciences, University of Illinois, Urbana, Illinois, United States of America
Roland Beffa
Affiliation: Weed Resistance Research, Bayer CropScience, Frankfurt am Main, Germany
Philip Westra
Affiliation: Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado, United States of America
Stephen B. Powles
Affiliation: Australian Herbicide Resistance Initiative, School of Plant Biology, University of Western Australia, Crawley, Western Australia, Australia
Introduction
Gene amplification, the reiteration of a coding segment resulting in one or more additional gene copies, is known to be a common process in the evolutionary history of plants and is vital for generating genomic diversity [1]. In addition to being a mechanism of adaptive evolution in mammalian cancer cells [2], bacteria [3], and arthropods [4], gene amplification is an important adaptive mechanism for antibiotic resistance, and the increased expression can offset fitness penalties associated with some resistance mechanisms [5]. Gene amplification and the resulting proportional increase in transcript levels has been implicated in insecticide resistance evolution in 10 different arthropod species, both for genes having a role in increased insecticide metabolism and for genes encoding proteins inhibited by insecticides (reviewed by [4]). Hence, numerous cases have been demonstrated where gene amplification has facilitated adaptive evolution.
Gene amplification is also an adaption in plants conferring resistance to the herbicide glyphosate [6]. Glyphosate is the world’s most important and widely used herbicide and persistent usage is resulting in resistance evolution [7]. An Amaranthus palmeri population highly resistant to glyphosate was found to have from 40- to 100-fold amplification of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene,...