Evolution of a Double Amino Acid Substitution in the 5-Enolpyruvylshikimate-3-Phosphate Synthase in Eleusine indica Conferring High-Level Glyphosate Resistance1

• Published in: Plant physiology (Bethesda) Vol. 167; no. 4; pp. 1440 - 1447
• Main Authors: Yu, Qin, Jalaludin, Adam, Han, Heping, Chen, Ming, Sammons, R. Douglas, Powles, Stephen B.
• Format: Journal Article
• Language: English
• Published: American Society of Plant Biologists 25.02.2015
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.15.00146

Naturally evolved double mutants in 5-enolpyruvylshikimate-3-phosphate synthase mimic engineered glyphosate-tolerant 5-enolpyruvylshikimate-3-phosphate synthase in crops and confer high-level glyphosate resistance. Glyphosate is the most important and widely used herbicide in world agriculture. Intensive glyphosate selection has resulted in the widespread evolution of glyphosate-resistant weed populations, threatening the sustainability of this valuable once-in-a-century agrochemical. Field-evolved glyphosate resistance due to known resistance mechanisms is generally low to modest. Here, working with a highly glyphosate-resistant Eleusine indica population, we identified a double amino acid substitution (T102I + P106S [ TIPS ]) in the 5-enolpyruvylshikimate-3-phosphate synthase ( EPSPS ) gene in glyphosate-resistant individuals. This TIPS mutation recreates the biotechnology-engineered commercial first generation glyphosate-tolerant EPSPS in corn ( Zea mays ) and now in other crops. In E. indica , the naturally evolved TIPS mutants are highly (more than 180-fold) resistant to glyphosate compared with the wild type and more resistant (more than 32-fold) than the previously known P106S mutants. The E. indica TIPS EPSPS showed very high-level (2,647-fold) in vitro resistance to glyphosate relative to the wild type and is more resistant (600-fold) than the P106S variant. The evolution of the TIPS mutation in crop fields under glyphosate selection is likely a sequential event, with the P106S mutation being selected first and fixed, followed by the T102I mutation to create the highly resistant TIPS EPSPS . The sequential evolution of the TIPS mutation endowing high-level glyphosate resistance is an important mechanism by which plants adapt to intense herbicide selection and a dramatic example of evolution in action.