Elevated antioxidant response and induction of tau-class glutathione S-transferase after glyphosate treatment in Vigna radiata (L.) Wilczek

Abstract

Glyphosate (N-(phosphonomethyl) glycine) is a broad-spectrum herbicide, acting on the shikimic acid pathway inhibiting 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), thus obstructing the synthesis of tryptophan, phenylalanine, tyrosine and other secondary products. It has also been reported to generate oxidative stress which influences the antioxidant response of target plants. The effect of glyphosate application on total protein, CAT, POD and GST activities was investigated and elevated expression of the oxidative stress enzymes was obtained after glyphosate treatment. Tau-class GSTs are plant-specific, and are chiefly involved in xenobiotics and oxidative stress metabolisms. Many herbicides and safeners have been known to selectively induce tau-class GSTs in different plant species. Here we also report the induction of tau-class GSTs after glyphosate treatment in the seedling roots of two Vigna radiata varieties (PDM11 and PDM54). GSH-agarose affinity chromatography and mass spectrometry revealed that the tau-class GSTs induced in the two varieties were different; the tau-class GSTs present in the untreated controls were also different in the two varieties. The present study highlights the elevated antioxidant response, the induction of tau-class GST and the genotypic variation in the type of tau-GST in control and glyphosate treated varieties of V. radiata.