Effects of phosphogypsum on the growth of potato plants overexpressing the StDREB1 transcription factor

Abstract

Phosphogypsum (PG) is an acidic industrial by-product, resulting from the production of phosphoric acid. In Tunisia, 10 million tons of PG are discarded yearly without any treatment. The Tunisian PG is characterized by its cadmium content of about 3.1–22.9 mg/kg. It is mainly stocked without any treatment near the production sites. Therefore, minimizing the negative impact of this waste has increasingly aroused the interest of many researchers. The use of PG as alternative phosphorous and sulfate fertilizer was envisaged. In this context, we have investigated the possibility of cultivating transgenic potato plants overexpressing the dehydration responsive element binding (StDREB1) protein on PG-supplemented substrates. Prewashed PG (WPG) was used to reduce the acidity of PG. Two WPG concentrations were used (15 and 30%) for potato culture during 60 days. The data show that WPG altered the survival rate of wild-type potato plants. Indeed, increasing the amount and treatment period of WPG led to a decrease in plant survival to 10% (after 60 days), while the survival rate of transgenic lines was about 50% with normal growth characteristics. Furthermore, an increase in proline and soluble sugar and reduced levels of H2O2 and malondialdehyde were measured in transgenic plants. An increase in antioxidant enzyme activities was observed in these transgenic lines revealing that they can cope with oxidative stress generated by phosphogypsum addition in the medium. A very low accumulation of Cd was detected in leaves of both transgenic lines. All these data suggest that overexpression of the StDREB1 transcription factor in transgenic potato plants improved their tolerance to WPG.