COAT BUTTONS (Tridax procumbens) with GROUP G/9 resistance: (INHIBITION OF ENOLPYRUVYL SHIKIMATE PHOSPHATE SYNTHASE ) Inhibition of EPSP synthase
MUTATION: THREONINE 102 to SERINE
Coat Buttons (Tridax procumbens) is a dicot plant in the asteraceae family. A single amino acid substitution from Threonine 102 to Serine has led to resistance to Inhibition of Enolpyruvyl Shikimate Phosphate Synthase as indicated in the table below.		Coat Buttons

Chemical Family	Example Herbicide	Resistance Level
Glycines	glyphosate	Intermediate Resistance < 10 fold

REFERENCES

Jingbo Li, Qiong Peng, Heping Han, Alex Nyporko, Tymofii Kulynych, Qin Yu, and Stephen Powles. 2018. Glyphosate resistance in Tridax procumbens via a novel EPSPS Thr-102-Ser substitution. Journal of Agricultural and Food Chemistry : .

This study confirmed the first case of glyphosate resistance in Tridax procumbens and investigated the glyphosate-resistance mechanisms. Sequencing and cloning of the full 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) coding sequences revealed a point mutation (ACC to TCC) at amino acid position 102, resulting in a novel Thr-102-Ser substitution. Other possible resistance mechanisms (i.e., target-site EPSPS-gene overexpression, nontarget-site differential glyphosate uptake and translocation) were also examined and were unlikely to be involved in resistance in this population. Structural modeling of the wild-type and mutant EPSPS in complex with glyphosate and phosphoenolpyruvate (PEP) revealed that the Thr-102-Ser substitution weakly decreased EPSPS affinity to glyphosate, but sharply increased EPSPS affinity to the natural substrate, PEP. Therefore, this novel mutation is very likely responsible for the observed glyphosate resistance in this tetraploid weed species via dual mechanisms of reducing glyphosate binding and favoring PEP binding to EPSPS..

This case was entered by Todd Gaines Email: todd.gaines@colostate.edu

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