Aluminum Toxicity in Soybean Cell Cultures
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Date
2001-02
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Central Research Institute for Food Crops
Abstract
Aluminum phytotoxicity is a major factor of the infertility of acid soils. The main toxic form of aluminum is the Al3* ion. Its occurrence strongly depends on the pH of the solution and the activity of other ions that can interact with Al3*. Simulating the mineral environment of aluminum-toxic soils in plant cell culture requires careful modifications to the standard culture medium. In principle, using such an aluminum-toxic medium it is possible to select for cell lines that show an increased resistance to aluminum Selection for aluminum resistance can be achieved by different strategies. In direct strategies cells are selected for their ability to actively grow in the presence of toxic concentrations of ionic aluminum. Rescue strategies involve a recovery of cells in normal medium that have survived a previous aluminum treatment. Different direct and rescue methods and required medium modifications for soybean cell cultures are presented and discussed with regard to arising problems and possible solutions. Aluminum ions cause a multitude of harmful changes to various cellular process. Despite intensive research a primary target of aluminum phytotoxicity has not been identified so far. Al1* can enhance the iron-mediated peroxidation of membrane lipids. In soybean cell cultures this stimulation of lip id peroxidation coincides with aluminuminduced cell death. Experiments with lipophilic antioxidants showed that soybean cells survived in the presence of cytotoxic levels of aluminum in the culture medium when lipid peroxidation was suppressed. This leads to the conclusion that aluminum toxicity In soybean cell cultures is at least partly mediated by an enhancement of lipid peroxidation The underlying mechanism of Al1* action could involve the increased formation of reactive oxygen species. In soybean cell cultures, however, aluminum treatment did not lead to a measurable formation of reactive oxygen species. Therefore, it seems more likely that direct interactions between A!1* and membrane lipids lead to changes in membrane structure that facilitate lipid peroxidation processes. The importance of different toxic effects of aluminum on soybean cells are discussed.
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Keywords
Aluminum toxicity, Glycine max, cell culture