Gene duplication and aneuploidy trigger rapid evolution of herbicide resistance in common waterhemp

Plant Physiol. Herbicide resistance is a serious problem in contemporary agriculture. One of the most widely used herbicides, glyphosate, interferes with the activity of EPSPS (5-enolpyruvylshikimate-3-phosphate synthase). Koo et al. previously showed that glyphosate-resistant waterhemp (Amaranthus tuberculatus, a common weed in agricultural fields) has an increased copy number of the EPSPS gene and an extra chromosome. In this new report, they demonstrate that the extra gene copies are found on small circular ring chromosomes of various sizes that can be passed between generations. The authors speculate on the mechanism of formation of these ring chromosomes including the involvement of the Breakage-Fusion-Bridge mechanism described initially by Barbara McClintock. (Summary by Mary Williams) Plant Physiol. 10.1104/pp.17.01668