Generation of transformed roots of Scirpus americanus Pers. and study of their potential to remove Pb2+ and Cr3+

In vitro root cultures of Scirpus americanus are capable to remove heavy metals. To improve metal uptake, this work focused on the production of transformed roots with the strain A4 of Agrobacterium rhizogenes containing the agropine-type plasmid pRiA4 and the binary vector pESC4. Materials used as explants included in vitro root cultures, seedlings grown under hydroponic conditions, and in vitro seedlings. Infection of in vitro root cultures failed to produce hairy roots, while the infection of greenhouse and in vitro seedlings induced 84 and 67 % GUS-positive hairy roots, respectively. From 31 clones obtained, clones T11, T12 and T14 expressed the genes nptII and rol B. As T12 exhibited a faster growth, it was selected for metal-uptake experiments. Clone T12 grown in the presence of metals removed 3.8 and 1.2 times more Pb and Cr, respectively, than non-transformed roots, suggesting that this clone displays more efficient tolerance mechanisms to Pb and Cr. Metal absorption was 4-6 fold higher than adsorption. Transgenic plants were regenerated from in vitro root cultures of clone T12. The use of hairy roots and transformed plants of S. americanus could provide an alternative strategy for the remediation of water contaminated with heavy metals.