EFFECT OF HEAVY METAL TREATMENTS ON METALLOTHIONEIN EXPRESSION PROFILES IN WHITE POPLAR (Populus alba L.) CELL SUSPENSION CULTURES

Abstract. Populus species and hybrids are intensively cultivated as sources of woody biomass and are good candidates for phytoremediation because of their rapid growth rate, extensive root system and ease of propagation and transformation. To date, the molecular mechanisms that regulate heavy metal tolerance have not been fully investigated. In the present work, white poplar (Populus alba L.) cell suspension cultures were used as model system to investigate the response to heavy metal treatments. The VFMT2 cDNA, encoding a type 2 metallothionein from P. alba, was isolated by RT-PCR approach. The expression profiles of the VFMT2 gene were then investigated by Quantitative Real Time Polymerase Chain Reaction (QRT-PCR) under oxidative stress conditions. The latter were induced by exposing the cell suspension cultures to different doses of cadmium (75 and 150 μM CdSO4), copper (50 and 100 μM CuCl2) and zinc (1 and 2 mM ZnSO4). Cell death was evidenced by Evans blue staining. The VFMT2 gene was up-regulated in response to heavy metal treatments and the highest mRNA level (up to 5-fold) was observed 4 h following exposure to 100 μM CuCl2