A red and far-red light receptor mutation confers resistance to the herbicide glyphosate.
Bottom Line: Glyphosate is a widely applied broad-spectrum systemic herbicide that inhibits competitively the penultimate enzyme 5-enolpyruvylshikimate 3-phosphate synthase (EPSPS) from the shikimate pathway, thereby causing deleterious effects.Furthermore, transcript analysis suggested that this diurnal oscillation was not only dependent on phyB but was also due to circadian regulatory mechanisms.Our data offer an explanation of the well documented observation that glyphosate treatment at various times throughout the day, with their specific composition of light quality and intensity, results in different efficiencies of the herbicide.
Affiliation: Department of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Jeddah, Saudi Arabia; Department of Horticulture and Landscape Architecture, Purdue University, 47907, West Lafayette, Indiana, USA.Show MeSH
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Mentions: Our previous results revealed that both the phyB-dependent mechanism and the circadian clock regulatory components are essential parts of the transcriptional regulation of shikimate pathway genes, and that defective phyB causes transcript accumulation in major components of the shikimate pathway in gre1 (Figures4 and S6). Thus, enhanced transcript accumulation is the most likely reason for the development of glyphosate resistance in gre1. In order to test this hypothesis, we performed glyphosate experiments on greenhouse grown plants that had been sprayed at different times. The growth inhibitory potential of the herbicide varied according to the time of day the spray was applied. The plant survival rates were determined based on the development of stem elongation (Figure5). In comparison with gre1 plants, growth of wt plants was arrested completely when they were sprayed 200 μm glyphosate (0.2535 mg m−2) during the first half of the day, whereas glyphosate spraying in late afternoon caused only a partial inhibition (Figure5a, b). When glyphosate was applied either at 5 or 9 o'clock (am) it was lethal to wt plants, however, all wt plants survived if the application occurred later. All gre1 plants survived regardless of the time of spray, however, the growth rate was still dependent upon the spray time; the least growth occurred if sprayed in the morning and better growth occurred at the later applications (Figure5a, b).
Affiliation: Department of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Jeddah, Saudi Arabia; Department of Horticulture and Landscape Architecture, Purdue University, 47907, West Lafayette, Indiana, USA.