engleski

Oxidative stress in Mammillaria gracillis tissues grown in vitro

In vitro propagated plants of Mammillaria gracillis Pfeiff. (Cactaceae) develop calli without any exogenous growth regulators. This habituated calli spontaneously regenerate morphologically normal and hyperhydric shoots. Since the habituation and hyperhydricity are both part of a neoplastic progression, cactus cells were transformed with A. tumefaciens wild strain B6S3. The aim of this study was to find out if activated oxygen metabolism is involved in the processes of habituation, hyperhydricity and tumourisation in in vitro propagated plants of Mammillaria gracillis Pfeiff. A significantly higher MDA and carbonyl contents as well as H2O2 production were observed in callus, hyperhydric regenerants and tumour in comparison to normal shoots. LOX activity showed a similar trend, with a clear increase in activity in callus and hyperhydric regenerants. The activities of antioxidative enzymes PPX (EC 1.11.1.7), APX (EC 1.11.1.11), GR (EC 1.8.1.7) and CAT (EC 1.11.1.6) were also higher in the callus, hyperhydric regenerants and tumour while an increase in SOD (EC 1.15.1.1) activity was observed in the callus and hyperhydric regenerants. PAL (EC 4.3.1.5) activity significantly decreased from normal shoot via callus to hyperhydric regenerants, being the lowest in tumour. Content of total phenols was also significantly lower in callus, hyperhydric tissue and tumour in comparison to normal tissue. Our results revealed a prominent oxidative stress in callus, hyperhydric regenerants and tumour as well as a strong induction of the antioxidant system indicating that ROS and activated oxygen metabolism are involved in the processes of habituation and hyperhydricity in M. gracillis as well as in tumour transformation.

oxidative stress; Mammillaria gracillis; plant tissue culture

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