Arabidopsis AtLTI30 and AtHIRD11 dehydrin genes and their contribution to cadmium tolerance in transgenic tobacco plants

We investigated the contribution of two Arabidopsis AtHIRD11 (AT1G54410, DH1) and AtLTI30 (AT3G50970, DH3) dehydrin genes to cadmium stress tolerance in plants. We generated two sets of transgenic tobacco plants overexpressing dehydrins DH1 and DH3. Transgenic and non-transgenic (control) plants were exposed to the long-term (50 µM cadmium chloride for 10 days) and short-term (100 µM cadmium chloride for 24 h) stress and analysed. Our results revealed that the dehydrin DH3 has modulated the cadmium uptake capacity of tobacco. The DH3 overexpressing plants absorbed cadmium significantly faster and in larger quantitates (at least 2.4-fold). Most of the absorbed cadmium was retained in the roots and not translocated to the leaves of DH3 plants. In root cells, a larger portion of cadmium was allocated in the soluble fraction consisting of cytosol and vacuoles, suggesting a potential role for DH3 in cadmium detoxification. An overexpression of the gene DH3 led to a significant (at least 6- and 2.6-fold) increase in the content of non-enzymatic antioxidants chlorogenic acid and rutin, respectively, under standard as well as stress conditions. Some of the cadmium-responsive miRNAs (nta-miR169q, nta-miR319b and nta-miR156g) were supressed in DH3 overexpressing plants, indicating a potential role for DH3 in modulating of plant's defence response. Unlike the DH3 gene, the contribution of the dehydrin DH1 to cadmium tolerance seems to be insignificant.