engleski

Oxidative Stress in Horseradish (Armoracia lapathifolia Gilib.) Tissues Grown in vitro

In a previous study it was reported that transformed tissue of horseradish (Armoracia lapathifolia Gilib.), obtained by infection of leaf explants with A. tumefaciens, developed two tumor lines with different morphology. One line still grows as a completely unorganized tissue (TN - tumor tissue), while the other line grows as a partially organized teratogenous tumor with malformed hyperhydric shoots (TM - teratoma tissue), but does not regenerate the whole plant of normal morphology. The factor responsible for this problem could be the increased production of reactive oxygen species (ROS). Therefore, in this study a possible involvement of activated oxygen metabolism in dedifferentiation and hyperhydricity in TM and TN tissues was investigated. Elevated values of malondialdehyde and protein carbonyl contents found in TM and TN, in comparison to plantlets leaf, confirmed the presence of oxidative stress. However, lower H2O2 content was measured in TM and TN. Lipoxygenase (LOX) activity was more pronounced in TM and especially in TN, compared to leaf, which suggests that the LOX-dependent peroxidation of fatty acids might be one of the causes of oxidative damage. Moreover, significantly higher peroxidase (PRX) and ascorbate peroxidase (APX) activity as well as the increased number of their isoforms was found in transformed TM and TN in comparison to leaf. On the other hand, significantly lower superoxide dismutase (SOD) activity was found in TM and TN which correlates with lower H2O2 content. High catalase (CAT) activity measured in leaf and partially organized TM is consistent with CAT role in growth and differentiation. In conclusion, in horseradish transformed tissues, that are undergoing dedifferentiation and hyperhydricity, prominent oxidative damage was found. This result suggests that oxidative stress could be associated with the inability of partially organized teratogenous TM to regenerate plantlets with normal morphology.

antioxidative enzymes; horseradish; isoenzyme pattern; oxidative stress; tissue culture; tumor tissue

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