Influence of Serratia liquefaciens and a xenobiotic glutathione conjugate on the detoxification enzymes in a hairy root culture of horseradish (Armoracia rusticana)

Plants are able to detoxify organic pollutants by conjugation reactions, e.g. mediated by glutathione S-transferases (GST). A significant fraction of the resulting metabolites reaches the rhizosphere, where they may impact other plants' roots and micro organisms in the root zone. In this work we investigated the influence of a xenobiotic conjugate, dinitrobenzene-glutathione, on sterile hairy root cultures of horse radish (Armoracia rusticana) and roots colonized with Serratia liquefaciens. When hairy roots were incubated with glutathione conjugates, we found that peroxidase activity for guajacol, GST-CDNB activity and dichloromethane detoxification were transiently induced during the first 6 hrs of treatment. Roots colonized with bacteria reacted faster than sterile roots. The ability of the roots to conjugate DCNB with glutathione was totally lost at the cost of p-NBOC activity. This is to our knowledge the first report on the synergistic effects of a soil bacterium and a xenobiotic conjugate on plant roots. Serratia is able to change the detoxification capacity of plant roots significantly and will by that influence the plant-rhizosphere metabolism of organic xenobiotics.