Root Growth of Transgenic Tobacco Plants with Overexpression of Expansin and Xyloglucan endotransglycosylase Genes under Cadmium Stress

Expansins and xyloglucan endotransglycosylases play an important role in the regulation of plant growth under optimal and stressful conditions. Transgenic tobacco plants overexpressing NtEXPA1 and NtEXPA5 expansin genes and NtEXGT xyloglucan endotransglycosylase of Nicotiana tabacum L. have been previously created by the authors. The aim of this work was the morphophysiological analysis of the roots of these transgenic tobacco plants under conditions of cadmium stress. Transgenic tobacco plants were characterized by increased root length compared to wild type plants, both under optimal conditions and when exposed to cadmium. The area of parenchyma cells of roots of transgenic tobacco plants overexpressing NtEXPA1 and NtEXPA5 expansin genes was greater than the wild type, while the cell sizes, on the contrary, were smaller in the case of the transgene NtEXGT. Overexpression of NtEXPA1,NtEXPA5, and NtEXGT genes contributed to an increase in the total antioxidant capacity and activity of ascorbate peroxidases and a decrease in the content of proline in the roots under the action of cadmium. In the shoots of plants transgenic for the expansin genes, a lower content of MDA was found both under optimal conditions and under the action of cadmium. Thus, it has been shown that NtEXPA1 and NtEXPA5 transgenes have a stimulating effect on the growth of tobacco roots under conditions of cadmium stress by enhancing cell expansion and a positive effect on the components of the antioxidant system. The NtEXGT gene is also involved in root growth under the action of cadmium, including through the effect on the antioxidant system.