Publication Date:
2012-02-28
Description:
To investigate the mechanism of cadmium (Cd) detoxification in rice ( Oryza sativa L.), a Cd-tolerant mutant cadH-5 , obtained by an Agrobacterium tumefaciens -based gene-delivery system, was used for a Cd-tolerance and accumulation study. After 15 d of exposure to 0.75 mM CdCl 2 , significant phenotypic differences were observed between the wild type (WT) and cadH-5. When exposed to 0.5 mM CdCl 2 , higher Cd levels were accumulated in cadH-5 root cell wall, root cytosol, and membranes than those in WT. However, Cd concentrations in root tissues varied in both WT and cadH5. No significant difference of hydrogen peroxide (H 2 O 2 ) concentrations was observed between WT and cadH-5 , while contents of cell-wall polysaccharides and phytochelatins (PCs) in the mutant were higher compared to WT. The ratios of reduced glutathione to oxidized glutathione (GSH : GSSG) and ascorbate to dehydroascorbate (ASC : DHA) were lower in WT than in cadH-5 , while the NADPH : NADP + ratio was different to the ratios of GSH : GSSG and ASC : DHA; the ascorbate peroxidase (APX, EC 1.11.1.11), glutathione peroxidase (GR, EC 1.6.4.2), dehydroascorbate reductase (DHAR, EC 1.8.5.1), and monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) activities were lower in WT compared to cadH-5. Our results indicate that under long-term Cd stress, cadH-5 plants can accumulate more Cd with more PC. Also, the redox status of ASC-GSH cycle was more inhibited in WT than in cadH-5 plants, rendering WT less able to scavenge reactive oxygen species (ROS). The cadH-5 mutant maintains relatively high ASC, GSH, and NADPH concentrations, ratios of ASC : DHA, GSH : GSSG, and NADPH : NADP + , as well as antioxidative enzymatic activities and PC concentrations. Thus, it is tolerant of relatively high Cd accumulation.
Print ISSN:
1436-8730
Electronic ISSN:
1522-2624
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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