The Changes of Tolerance, Accumulation and Oxidative Stress Response to Cadmium in Tobacco Caused by Introducing Datura stramonium L. Genes

Abstract

Whether it is possible to create suitable plants for cadmium phytoremediation by introducing Datura stramonium L. genes into tobacco (Nicotiana tabacum L.) remains unclear. Hydroponic experiments were performed on N. tabacum L. var. MTLY, a newly developed hybrid variety, and the parents. Seedlings at the six-leaf stage were treated with 0 (control), 10 µM, 180 µM and 360 µM CdCl2 for 7 days, and their differences in Cd tolerance and accumulation and physiological and metabolic responses were evaluated. When subjected to 360 µM Cd, the growth of “MTLY”, in terms of the dry weight, plant height and root length, was obviously better than N. tabacum L. var. LY2 (female parent). In contrast to D. stramonium (male parent) and “LY2”, “MTLY” accumulated more Cd in shoots (127.6–3837.1 mg kg−1) and roots (121.6–1167.7 mg kg−1). Moreover, unlike “LY2”, “MTLY” could accumulate more Cd in its shoots than roots. Its bioconcentration factor (BCF) and translocation factor (TF) values reached 95.9–149.7 and 1.0–3.5, respectively, which were far greater than those of “LY2”. High-dose Cd stress significantly increased reactive oxygen species (ROS) and malondialdehyde (MDA) levels and decreased chlorophyll contents in tobacco seedlings, especially in “LY2”. Various enzymatic and non-enzymatic antioxidants in the three materials showed different responses to Cd stress. The change of the phenolic compounds and alkaloids in “MTLY” was basically similar to that in D. stramonium, but their levels were apparently higher than those in “LY2”. Results indicated that distant hybridization could be one of the effective methods for introducing metal-hyperaccumulator genes into a high biomass species, which contributed to enhancing the Cd tolerance, accumulation and detoxification in tobacco. This study has great significance in obtaining elite germplasm for phytoremediation. The exact mechanisms in molecules and genetics and the practical effectiveness in cadmium-contaminated soil remain to be further elucidated.