Expression of Arabidopsis acyl-CoA-binding proteins AtACBP1 and AtACBP4 confers Pb(II) accumulation in Brassica juncea roots

In Arabidopsis thaliana, the expression of two genes encoding acyl-CoA-binding proteins (ACBPs) AtACBP1 and AtACBP4, were observed to be induced by lead [Pb(II)] in shoots and roots in qRT-PCR analyses. Quantitative GUS (-glucuronidase) activity assays confirmed induction of AtACBP1pro::GUS by Pb(II). Electrophoretic mobility shift assays (EMSAs) revealed that Pas elements in the 5-flanking region of AtACBP1 were responsive to Pb(II) treatment. AtACBP1 and AtACBP4 were further compared in Pb(II) uptake using Brassica juncea, a potential candidate for phytoremediation given its rapid growth, large roots, high biomass and good capacity to accumulate heavy metals. Results from atomic absorption analyses on transgenic B.juncea expressing AtACBP1 or AtACBP4 indicated Pb(II) accumulation in roots. Subsequent Pb(II)-tracing assays demonstrated Pb(II) accumulation in the cytosol of root tips and vascular tissues of transgenic B.junceaAtACBP1-overexpressors (OXs) and AtACBP4-OXs and transgenic ArabidopsisAtACBP1-OXs. Transgenic ArabidopsisAtACBP1-OXs sequestered Pb(II) in the trichomes and displayed tolerance to hydrogen peroxide (H2O2) treatment. In addition, AtACBP1 and AtACBP4 were H2O2-induced in the roots of wild-type Arabidopsis, while lipid hydroperoxide (LOOH) measurements of B.junceaAtACBP1-OX and AtACBP4-OX roots suggested that AtACBP1 and AtACBP4 can protect lipids against Pb(II)-induced lipid peroxidation. Arabidopsis acyl-CoA-binding proteins, AtACBP1 and AtACBP4, have been shown to bind lead [Pb(II)] in vitro, prompting us to investigate their potential in Pb(II) phytoremediation. Our results showed that AtACBP1 and AtACBP4 were induced by Pb(II) and putative elements responsive to Pb(II) were identified in the 5-flanking region of AtACBP1. Transgenic Arabidopsis overexpressing AtACBP1 sequestered Pb(II) in the trichomes and displayed tolerance to hydrogen peroxide (H (2) O (2)) treatment, whereas transgenic Brassica juncea overexpressing AtACBP1 or AtACBP4 sequestered Pb(II) in the cytosol of root tips and vascular tissues, and displayed Pb(II) accumulation in roots. In addition, AtACBP1 and AtACBP4 were induced by H (2) O (2) in roots of wild-type Arabidopsis and transgenic B. juncea overexpressing AtACBP1 or AtACBP4 were protected against Pb(II)-induced lipid peroxidation.