RESUMEN
The aim of the study was to evaluate the long-term effect of Agrobacterium rhizogenes genes transfer on plant antioxidant system by the study of superoxide dismutase (SOD) activity in "hairy" roots of Artemisia and Althaea spp plants. PCR analyses revealed stability of the transformation and presence of bacterial rol B and rol C genes in the "hairy" roots after 4-6 years from the transformation event. SOD activity in the roots of untransformed in vitro cultivated plants used for the initiation of "hairy" roots growth was in the range of 45.8 ± 8.7 U/µg (Althaea officinalis) and 275 ± 97.1 U/µg (Artemisia ludoviciana). After a long-term in vitro cultivation more than half of tested "hairy" root lines (54%) showed a significant increase in SOD activity values compared to untransformed roots. The highest SOD activity values of "hairy" root lines (24-fold increase) were founded in A. officinalis (1105 ± 174 U/µg) and A. dracunculus (1356 ± 402 U/µg). The increase of the activity was found also in "hairy" roots of A. vulgaris (up to 375 ± 28.2 U/µg, sevenfold increase), A. ludoviciana (1001 ± 191 U/µg, 3.6-fold increase), and A. tilesii (438 ± 104 U/µg, 1.6-fold increase). The results of our study indicate that transformation by wild-type A. rhizogenes not harboring any foreign genes implementing in SOD activity regulation can often stably activate plant antioxidant enzyme system. This effect, observed in the "hairy" roots of five plant species in 4-6 years of the transformation event, obviously, should be taken into account in works aimed at creating transgenic plants by Agrobacterium-mediated transformation.