Transcript accumulation of stress-related genes in Vicia faba roots under a short exposure to cadmium

Messenger RNA accumulation of various stress-related protein genes was monitored in response to Cd in Vicia faba plants. Metal treatment induced reactive oxygen species (ROS) production. H2O2 accumulated 12h after the Cd exposure in Vicia roots proportionally to intracellular Cd content of treated plants and O-2(-) by 24h. The time course of oxidative stress evidenced by malondialdehyde (MDA) content indicated that lipoperoxidation occurred 24h after Cd treatment. Prior to oxidative burst, the metal induced a similar dose-dependent kinetic of transcript accumulation for Hsp70.1, MT2, GR1 and Cu-ZnSOD genes with a rapid increase or response at 12h of Cd treatment, whereas the prolonged exposure to Cd resulted in reduction in the mRNA levels for all four genes. The pattern of Cat transcript accumulation was different from the other four genes and correlated with the intracellular oxidative burst. Cat transcripts were accumulated at 24h in the Vicia roots, and this antioxidative enzyme gene was at high level of expression till the end of treatment concomitantly to ROS overproduction and MDA accumulation. The results indicate two different gene expression pathways activated by Cd-induced abiotic stress conditions and might be related to the cell oxidative status.