Protein identification before and after glyphosate exposure in Lolium multiflorum genotypes.

Background: Weeds reduce crop yields, and among the methods used to control these plants, the use of chemicals is preferred. However, the repeated application of herbicides with the same mechanism of action selects for resistant populations. The aim of this study was to evaluate glyphosate resistance in Lolium multiflorum (Lam.) and relate the resistance to protein expression in the absence and presence of the herbicide using a metabolic-proteomic approach.

Results: Glyphosate resistance was confirmed, with a sevenfold difference in resistance between susceptible and resistant genotypes. Among the possible mechanisms affecting resistance, mutations in the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), herbicide differential translocation and overexpression of EPSPS are suggested. Susceptible plants had higher growth than did resistant plants in the absence of the herbicide, in addition to greater expression of protein groups related to photosynthesis and to tolerance to biotic and abiotic stresses. With application of glyphosate, resistant plants maintained their metabolism and began to express EPSPS and other candidate proteins related to herbicide resistance.

Conclusions: In the absence of glyphosate, the susceptible plants would replace the resistant plants over time, and abiotic or biotic stresses would accelerate this process. Resistance in plants resulted from a combination of target-site and non-target-site resistance mechanisms. We identified several candidate proteins that could be investigated in future studies on glyphosate resistance. © 2017 Society of Chemical Industry.