Studies On Physiological Function Of Arabidopsis Vtc1 Mutant Under UV-B Radiation

Ultraviolet-B (UV-B) radiation has a negative impact on plant cells, and results in the generation of reactive oxygen species (ROS). In order to increase our understanding of the effects of UV-B on antioxidant processes, we investigated the response of an ascorbate-deficient Arabidopsis thaliana mutant vtc1 to short-term increased UV-B exposure. After UV-B supplementation, vtc1 mutants exhibited more oxidative damage than wild type (WT) plants. H₂O₂ content and the production of thiobarbituric acid reactive substances (TBARS) were increased more in the mutant. More pronunciated decrease in chlorophyll contents and maximum photochemical efficiency of PSII was observed in the vtc1 mutant than WT plants. The decreased NPQ in the mutant under UV-B radiation suggest that photoprotection was impaired. The vtc1 mutants had higher total glutathione than the WT plants during the first day of UV-B treatment. Reduced ratio of glutathione/total glutathione and increased ratio of dehydroascorbate/total ascorbate in the vtc1 mutants were detected compared with the WT plants. In addition, the enzymes responsible for ROS scavenging, including superoxide dismutase, catalase, and ascorbate peroxidase, had decreased activity in the vtc1 mutants, compared to the WT plants. The same reduced activity in the vtc1 mutants was detected for the enzymes responsible for the regeneration of ascorbate and glutathione (including monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase). These results suggest that the ascorbate-deficient mutant vtc1 is more sensitive to supplementary UV-B treatment than WT plants and ascorbate can be considered an important antioxidant for UV-B radiation.