The role of oxidative stress induced by growth regulators in the regeneration process of wheat

As part of work to optimize the regeneration processes of winter wheat callus culture the effects of two auxins (2,4-D, IAA), two cytokinins (kinetin, zeatin), and the fungal mycotoxin zearalenone, were tested individually in vitro using embryo-, and inflorescence-derived callus. To determine the role of oxidative stress in cell regeneration, changes in the basic antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and peroxidases (PODs) were investigated. In general, zearalenone (ZEN) was found to be more effective than cytokinin treatments for inducing shoot production, whereas auxins suppressed the regeneration process. Regenerating callus showed higher induction of these antioxidant enzymes in comparison with non-regenerating callus. SOD, CAT and POD activities were higher in callus derived from inflorescence than in callus derived from immature embryo. Activities of SOD, CAT and POD in culture derived from immature embryos were depending on type of growth regulator in medium. The highest enzyme activities were observed in non-regenerating tissues after auxins treatment and in regenerating tissues after cytokinins treatment. The effect of ZEN was similar to that of cytokinins. One MnSOD band and two Cu/ZnSOD bands were detected in all cultures. Changes in SOD izoform patterns occurred in callus culture on media with auxins and ZEN, but not on media with cytokinins. Our results suggest that callus regeneration is associated with reactive oxygen species production induced by specific growth regulators. Reactive oxygen species under the control of cellular antioxidant machinery can mediate signalling pathways between exogenously applied growth regulators and the induction and/or creation of the direction of morphogenesis.