Molecular characterization of Arabidopsis and Brassica juncea Cu/Zn-superoxide dismutases reveals their regulation of shoot regeneration

Abstract

Superoxide dismutases (SODs) are ubiquitous metalloenzymes that catalyze the dismutation of superoxide radicals (O 2 - ) to molecular oxygen (O2) and hydrogen peroxide (H2O 2). In this study we characterized an Arabidopsis thaliana CuZnSOD (CSD1), a close ortholog of a previously identified Brassica juncea CuZnSOD (MSOD1). CSD1 and other two homologs CSD2 and CSD3 were spatially regulated in Arabidopsis, and CSD1 exhibited distinct expression patterns in response to different stress treatments. To investigate the in vivo function of SOD, transgenic Arabidopsis plants, expressing sense and antisense MSOD1 RNAs, were generated and those with altered SOD activity were selected for further characterization. Although SOD transgenic plants exhibited normal phenotypes, the shoot regeneration response in transgenic explants was significantly affected by the modulated SOD activity and the corresponding H2O 2 levels. Transgenic explants with downregulated SOD activity were poorly regenerative, whereas those with upregulated SOD activity were highly regenerative. These results suggest that shoot regeneration in vitro is regulated by the SOD activity. © 2007 Springer Science+Business Media, LLC.