Occurrence and Charactrisation of Superoxide Dismutases in the Female Reproductive Structures of Petunia

Abstract

Superoxide Dismutase (SOD) activity in cell-free extracts prepared from healthy mature flowers of Petunia hybrida (variety 'Hurrah') was studied. The SOD activity in the crude extracts was stable for more than one month when stored at -20 oC. It was found that pH 7.8 is optimal for SOD activity. Different flower tissues of petunia (stigma, style and ovary) at various stages of development were extracted and analysed for SOD activity. SOD activity was found to be significantly highest in the ovary tissue of dehiscent petunia flowers. Three SOD isozymes were detected after crude extracts of the different female reproductive tissues of petunia flowers were analysed on a non-denaturing polyacrylamide gel electrophoresis system. Based on a difference in the sensitivity of the SOD isoforms to H2O2 and KCN, it is suggested that Mn-SOD, Fe-SOD and Cu/Zn-SOD were present in the crude extracts of the female reproductive tissues of petunia flowers. The response of the female reproductive parts of petunia flowers was also tested under water deficiency and high temperature (35 oC) stress. The SOD activity seemed to increase more in response to the high temperature than the water deficiency stress. Intense blue staining was observed from developing younger buds, and much lower formazan deposition was detected at the later stage. This indicates the lower O2- produced during later stages mainly due to increasing SOD synthesis. DEAE cellulose chromatography was successfully used to partially purify SOD from the ovaries of petunia flowers. The characteristics of the partially purified enzyme fraction were found to be very similar to those of the crude extracts.