Overexpression of a basic peroxidase in transgenic tomato (Lycopersicon esculentum Mill. cv. Pera) hairy roots increases phytoremediation of phenol

In recent years, genetic engineering and tissue culture techniques have produced significant biotechnological advances in phytoremediation. Numerous peroxidases (E.C. 1.11.1.7) have been implicated in the phytoremediation of phenol, a common and highly toxic contaminant present in industrial wastewaters. To explore the possibility of enhancing phenol removal and to find out if tpx1, a basic (pI 9.6) peroxidase from tomato, is involved in phenol removal, we established transgenic tomato hairy root clones which overexpress tpx1 gene, following an unusual procedure: successive transformation with Agrobacterium tumefaciens and Agrobacterium rhizogenes. The overexpression of tpx1 correlated with higher in vivo and in vitro peroxidase activity in crude extracts (CE) of transgenic hairy root clones than in those of the wild type culture. Furthermore, peroxidase zymograms of transgenic clones showed higher activity of a band with pI 9.6 in the fraction of ionically bound to cell wall proteins. The transgenic clones with the highest peroxidase activity (clones 8 and 9) were selected and tested for phenol removal from aqueous solutions. Removal efficiency of the transgenic clone 8 was significantly higher than the wild type hairy roots. The data presented here provide evidence of the utility of successive transformation for obtaining stable transgenic hairy roots and demonstrate that engineered hairy root cultures overexpressing tpx1 peroxidase enhance phenol removal and could be useful tools in phytoremediation process.