CHANGES OF SHIKIMATE PATHWAY IN GLYPHOSATE TOLERANT ALFALFA CELL-LINES WITH REDUCED EMBRYOGENIC ABILITY

Glyphosate tolerant cell lines were selected from highly embryogenic c ell suspension culture of Medicago sativa L. Resistant cell lines show ed significant reduction of embryogenic ability and during long-term c ulture in the presence of glyphosate gradual loss of this ability was observed. After glyphosate treatment the increased activity of 5-enolp yruvylshikimate-3-phosphate synthase in tolerant cell lines overcame t he block in aromatic amino acid synthesis which was observed in contro l cell lines. Glyphosate caused marked increase in the content of shik imic acid in both control and tolerant cell lines but the accumulation of shikimic acid was considerably lower in tolerant calli. Significan t qualitative and quantitative differences were found in the content o f individual phenolic acids. The considerable decrease in the amount o f cinnamic acid derivates and broader spectrum of hydroxybenzoic acids suggest in tolerant cell lines the activation of alternative pathway not regulated by phenylalanine ammonia lyase. The possible role of alt ered pool of phenolic acids on the embryogenic ability is discussed.