JXB Advance Access originally published online on November 1, 2005
Journal of Experimental Botany 2005 56(422):3041-3049; doi:10.1093/jxb/eri301
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RESEARCH PAPER |
Increased sensitivity to salt stress in an ascorbate-deficient Arabidopsis mutant
1Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, 730000, China
2School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
* To whom correspondence should be addressed at the School of Life Sciences. Fax: +86 931 8912823. E-mail: zhanglixin{at}lzu.edu.cn
The Arabidopsis thaliana ascorbate-deficient vtc-1 mutant has only 30% ascorbate contents of the wild type (WT). This ascorbate-deficient mutant was used here to study the physiological roles of ascorbate under salt stress in vivo. Salt stress resulted in a more significant decrease in CO2 assimilatory capacity in the vtc-1 mutant than in the WT. Photosystem II function in the Arabidopsis vtc-1 mutant also showed an increased sensitivity to salt stress. Oxidative stress, indicated by the hydrogen peroxide content, increased more dramatically in the vtc-1 mutant than in the WT under salt stress. To clarify the reason for the increased oxidative stress in the vtc-1 mutant, the contents of small antioxidant compounds and the activities of several antioxidant enzymes in the ascorbate–glutathione cycle were measured. Despite an elevated glutathione pool in the vtc-1 mutant, the ascorbate contents and the reduced form of ascorbate decreased very rapidly under salt stress. These results showed that the activities of MDAR and DHAR were lower in the vtc-1 mutant than in the WT under salt stress. Thus, low intrinsic ascorbate and an impaired ascorbate–glutathione cycle in the vtc-1 mutant under salt stress probably induced a dramatic decrease in the reduced form of ascorbate, which resulted in both enhanced ROS contents and decreased NPQ in the vtc-1 mutant.
Key words: Arabidopsis thaliana, ascorbate–glutathione cycle, oxidative stress, photosystem II, vtc-1
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