Overexpression of the iron transporter NtPIC1 in tobacco mediates tolerance to cadmium.

KEY MESSAGE: Overexpression of the iron transporter NtPIC1 increases iron concentration in shoots and reduces Cd uptake/accumulation in plants, mediating tolerance to cadmium. Cadmium (Cd) is toxic to plant cells and causes plants to display a typical iron (Fe) deficiency phenotype. NtPIC1 (Permease In Chloroplast1) is an Fe transporter protein in tobacco, required for Fe homeostasis. Based on preliminary results in transformed Saccharomyces cerevisiae BY4741 cells, which showed that NtPIC1 expression increased Cd tolerance, this study evaluated Cd tolerance in tobacco plants overexpressing NtPIC1 (NtPIC1-OE). We show that these plants have longer roots and higher fresh weights than wild-type (WT) plants after Cd exposure. Under Cd stress, WT plants display more chlorosis, stronger growth inhibition, and lower chlorophyll concentrations than NtPIC1-OE plants. Importantly, NtPIC1-OE plants had higher Fe concentrations in shoots and lower Fe concentrations in roots, and Cd concentrations in NtPIC1-OE plants were significantly lower compared to those in WT plants. Moreover, Fe transport-related genes (NtPIC1, NtNRAMP1, and NtFER1) were upregulated in NtPIC1-OE plants, while Fe deficiency-related genes (NtFRO1, NtIRT1, and NtZIP1) that mediate Cd uptake were downregulated. We also found that the activities of several antioxidative enzymes were significantly higher in NtPIC1-OE plants than in WT plants under Cd stress. Overall, our results demonstrate that overexpression of NtPIC1 is an efficient way to increase shoot Fe concentrations and reduce Cd uptake/accumulation in plants.