| Catalases (H2O2: H2O 2 oxidoreductase, EC 1.11.1.6; CAT) are heme-containing tetramers that are important in destroying H2O2 found in different cellular compartments. Maize Cat3 has been shown to be capable of dismutating H2O2 via either a catalatic or peroxidatic reaction. In addition, increased maize CAT3 transcripts were detected during periods of chilling acclimation. In this study, a maize Cat3 cDNA was isolated using reverse transcriptase polymerase chain reaction. To better understand the role of maize CAT3 in oxidative stress, we have introduced the transgene that expresses this enzyme into wild type tobacco, Xanthi NN (Nicotiana tabacum). Total catalase activities were only slightly higher in transgenic plants as compared to Xanthi NN. While total peroxidatic activity of these transgenic plants was found to be 12-fold higher than in the wild-type tobacco. The transgenic Cat3 plants were exposed to various abiotic stresses such as, low temperatures, high temperatures, salinity, chemical treatments, and photooxidation. Increased seedling growth was evident in transgenic seedlings during treatments at low temperatures, high temperatures, and salt treatment which could implicate increased protection from oxidative damage. No significant protection was evident when treated with methyl viologen or photooxidative stress. In addition, lower lipid peroxidation levels in transgenic plants correlate with increased peroxidatic activity in these plants. These data suggests that maize CAT3 expressed in wild-type tobacco have increased protection against various forms of oxidative stress. |
