The effect of cadmium on transgenic potato (Solanum tuberosum) plants overexpressing the StDREB transcription factors

Cadmium (Cd) is a toxic heavy metal naturally present in soils. It causes environmental pollution because of the increase of mining and industrial activities in the twentieth century. Although plants do not require Cd, they can accumulate high levels of this metal. The response of plants to Cd pollution involves several signaling pathways involving stress responsive transcription factors. Among these transcription factors, it has been reported that DREB (drought-responsive element binding) factors are involved in plant response to abiotic constraints. In this context, in previous studies, we isolated and characterized two DREB genes from potato that were designated StDREB1 and StDREB2. Their overexpression in transgenic potato lines led to enhanced drought and salt stress tolerance in comparison to untransformed plants. These DREB transcription factors play crucial regulatory roles in different stress responsive pathways in potato. The goal of this report is to study the response of these transgenic potato plants overexpressing StDREB1 and StDREB2 to Cd stress. Therefore, transgenic plants and control plants were cultivated in vitro in MS (Murashige and Skoog) medium supplemented with 50-150 A mu M CdCl2. After 7 and 14 days of treatment, plant tissues were used to evaluate a number of physiological parameters. Transgenic plants submitted to Cd stress, showed lower decrease in growth, chlorpophyll and carotenoid content than wild-type (WT) plants. Similarly, almost no loss of water content was measured in BF3, SP1 and SPM lines. All transgenic plants exhibited lower H2O2 content and higher antioxidant enzyme expression than WT. A higher proline content was also measured in these plants after Cd treatment in comparison to WT. All these data suggest that overexpression of the StDREB genes improves tolerance of potato plants to Cd by improving plant growth, proline and antioxidant production leading to low oxidative stress damage.