Effect of glyphosate on the activity of DAHP synthase isozymes in callus cultures of groundnut (<i>Arachis hypogaea </i>L.) selected <i>in vitro</i>

Abstract

Two isozymes of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHP synthase or DS, EC 4.1.2.15) from the callus cultures of <i>Arachis hypogaea </i>L. were resolved by DEAE cellulose column chromatography and characterized using selective assays based on divalent cation requirements and regulation by the end-product amino acids. The total extractable activity of DAHP synthase did not show any change in the glyphosate sensitive and tolerant cell lines when compared to 5-enolpyruvylshikimate-3-phosphate synthase (EPSP synthase, EC 2.5.1.19), the known target of inhibition by glyphosate. However, the activities of both, DAHP synthase and EPSP synthase were inhibited by glyphosate <i>in vitro. </i>The inhibitory effects of glyphosate on the activities of (a) EPSP synthase and DAHP synthase, and (b) isozymes of DAHP synthase, have been compared. The data indicate that the Co²⁺ dependent isozyme of DAHP synthase is a putative target for the action of glyphosate in <i>A. hypogaea.</i>