Molecular and biochemical characterization of tomato (Solanum lycopersicum L.) plants cv. Micro-Tom under lead (Pb)-induced stress

Two different Pb concentrations (5 and 10 mg/kg of PbAc2) were used to study the response of Solanum lycopersicum L. cv. Micro-Tom (MT) plants in two vegetative growth phases. Two genes that have been previously reported to be heavy metal inducible genes (superoxide dismutase, SOD, EC 1.15.1.1; and isofl avone reductase, IFR; EC 1.6.4.2) and another one putatively interesting in this fi eld (transcriptionally controlled tumor protein, TCTP) were selected for an expression study using a real time PCR technique. In the fi rst growth phase (germination to fl owering) TCTP was repressed at 10 mg/kg and in the control, SOD expression was low at both concentrations (5 and 10 mg/kg of PbAc2) and IFR was higher at 10 mg/kg PbAc2. In the second phase (fl owering to fructifi cation) three genes were expressed in both concentrations but in the case of TCTP and SOD the expression was higher at 5 mg/kg of PbAc2. SOD and Glutathione reductase (GR; EC 1.6.4.2) were selected for a biochemical study together with the determination of protein concentration using spectrophotometer. SOD was higher at 10 mg/kg PbAc2 showing signifi cant difference with control, and GR had the same behavior but had signifi cant differences with the other two treatments while total proteins were higher for the control showing signifi cant differences at 10 mg/kg of PbAc2. This research suggests that Pb toxicity leads to the induction of key enzymes of antioxidant defense system in tomato plants.