Cadmium resistance in transgenic tobacco plants enhanced by expressing bean heavy metal-responsive gene PvSR2.

PvSR2 (Phaseolus vulgaris stress-related gene) has been cloned from French bean and shown to be expressed specifically upon heavy metal treatment. In order to investigate the role of PvSR2 in plant, PvSR2 gene under the control of cauliflower mosaic virus 35S promoter was introduced into tobacco mediated with Agrobacterium tumefaciens LBA4404. The regenerated plantlets were selected on medium with 100 mg/L kanamycin. PCR and Southern blot analysis showed PvSR2 gene was integrated in tobacco genome. Gus and Northern blot analysis indicated PvSR2 gene was expressed in transgenic seedling. The heavy metal resistance assay showed that the transgenic tobacco seedlings with the PvSR2 coding sequence exhibited higher tolerance to Cd compared with wild-type (WT) under Cd exposure. The Cd content accumulated in root between transgenic and WT seedlings had no obvious difference at lower Cd external concentration (0.05-0.075 mmol/L CdCl(2)), whereas transgenic plant showed a lower root Cd content than the control at higher external Cd concentration (0.1 mmol/L CdCl(2)). These results suggested that the expression of PvSR2 can enhance the Cd tolerance, and PvSR2 may be involved in Cd transportation and accumulation at the test concentration of 0.1 mmol/L Cd.