Uranium(VI) toxicity in tobacco BY-2 cell suspension culture - A physiological study.

For the first time, the physiological and cellular responses of Nicotiana tabacum (BY-2) cells to uranium (U) as an abiotic stressor were studied using a multi-analytic approach that combined biochemical analysis, thermodynamic modeling and spectroscopic studies. The goal of this investigation was to determine the U threshold toxicity in tobacco BY-2 cells, the influence of U on the homeostasis of micro-macro essential nutrients, as well as the effect of Fe starvation on U bioassociation in cultured BY-2 cells. Our findings demonstrated that U interferes with the homeostasis of essential elements. The interaction of U with BY-2 cells confirmed both time- and concentration-dependent kinetics. Under Fe deficiency, a reduced level of U was detected in the cells compared to Fe-sufficient conditions. Interestingly, blocking the Ca channels with gadolinium chloride caused a decrease in U concentration in the BY-2 cells. Spectroscopic studies evidenced changes in the U speciation in the culture media with increasing exposure time under both Fe-sufficient and deficient conditions, leading us to conclude that different stress response reactions are related to Fe metabolism. Moreover, it is suggested that U toxicity in BY-2 cells is highly dependent on the existence of other micro-macro elements as shown by negative synergistic effects of U and Fe on cell viability.