Ex planta phytoremediation of trichlorophenol and phenolic allelochemicals via an engineered secretory laccase

Plant roots release a range of enzymes capable of degrading chemical compounds in their immediate vicinity(1-2). We present a system of phytoremediation ex planta based on the overexpression of one such enzyme, a secretory laccase. Laccases catalyze the oxidation of a broad range of phenolic compounds(3), including polychlorinated phenols such as 2,4,6-trichlorophenol (TCP), that are among the most hazardous and recalcitrant pollutants in the environment(4). We isolated a secretory laccase cDNA of LAC1, which is specifically expressed in the roots of Gossypium arboreum (cotton). Transgenic Arabidopsis thaliana plants overexpressing LAC1 exhibited enhanced resistance to several phenolic allelochemicals and TCP. The secretory laccase activity in these plants was responsible for the conversion of sinapic acid into a mono-lactone type dimer and for the transformation of TCP.