Altered Expression of Superoxid Dismutase (SOD) Isoforms Is Necesary For Better Performance of A Recently Developed Drought-Tolerant Mutant of Rice Under Dehydration Stress

Abstract

Drought is one of the most important abiotic stresses, which annually reduces agriculture production worldwide. With regard to the occurrence of successive drought stress in the life period of crop plants, dealing with the stress, particularly in rice growing regions needs special attention. Therefore, this study aimed to investigate and to compare a recently-developed drought-tolerant mutant line under dehydration stress with its original parental cultivar (Neda). Mutant line performed better than its original parental cultivar Neda at seedling and whole plant stages under dehydration and drought stresses, respectively. For gene expression analysis, dehydration stress was mimicked by polyethylene glycol 6000 (osmotic pressure of -6 bar), and sampling was done at 0, 12, 24 and 36 hours after the stress, and expression of two isoforms of superoxide dismutase (SOD) gene was evaluated by real-time quantitative PCR method. Assessment of relative expression of superoxide dismutase isoform OsMnSOD at different times after stress showed that the expression of this gene in the parental cultivar was not significantly altered after the stress, while in the mutant line MT149 it was significantly decreased within early hours after stress but was significantly increased up to 11-fold within 24 hours after stress, and the expression of another isoform of superoxide dismutase, OsCu-ZnSOD, in mutant line MT149 also was first decreased and then increased up to 9-fold within 24 hours after stress. On the basis of the results of this research it can be concluded that probably one of the reasons for higher drought/dehydration tolerance of the mutant MT149 compared to Neda, is the increased expression of both isoforms of OsMnSOD and OsCu-ZnSOD within first 24 hours of exposing to the stress, making it possible to overcome the toxic effects of reactive oxygen species (ROS).