Molecular aspects of aluminum toxicity

Haug, A.; Foy, Charles E.

doi:10.1080/07352688409382184

Cited by 329 publications

(195 citation statements)

References 149 publications

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“…Toxic effects of aluminium on various organisms are well known (for reviews see Foy et al, 1978;Haug, 1984), but the mechanisms of its uptake, distribution in the cell and metabolic effects have not yet been evaluated.…”

Section: Introductionmentioning

confidence: 99%

Accumulation of Aluminium by Anabaena cylindrica into Polyphosphate Granules and Cell Walls: an X-ray Energy-dispersive Microanalysis Study

et al. 1985

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Section: Introductionmentioning

confidence: 99%

Accumulation of Aluminium by Anabaena cylindrica into Polyphosphate Granules and Cell Walls: an X-ray Energy-dispersive Microanalysis Study

et al. 1985

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“…One of the first symptoms of stress is the inhibition of root growth, which can begin within hours or minutes, provided the root apex is directly exposed to A1 . A1 is known to affect many cellular functions, and determining which one of these interactions is the primary cause of toxicity continues to be an important goal (Haug, 1984; Haug and Caldwell, 1985;Taylor, 1988;Kochian, 1995). These investigations often require reliable estimates of AI uptake into the symplasm, but the capacity for the cell wall to accumulate high concentrations of cations makes the resolution of apoplasmic and symplasmic fractions difficult (Dainty and Hope, 1959; Zhang and Taylor, 1990; Reid and Smith, 1992).…”

mentioning

confidence: 99%

Direct Evaluation of the Ca2+-Displacement Hypothesis for Al Toxicity

1997

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One explanation for AI toxicity in plants suggests that AI displaces ca'+ from critical sites in the apoplasm. We evaluated the Ca'+-displacement hypothesis directly using near-isogenic lines of wheat (Triticum aestivum L.) that differ in AI tolerance at a single locus. We measured both the growth and total accumulation (apoplasmic plus symplasmic) of 45Ca and AI into roots that had been exposed to AI alone or to AI with other cations. Root growth in the AI-sensitive line was found to be severely inhibited by low activities of AI, even though Ca'+ accumulation was relatively unaffected. In solutions containing the same activity of the AI3+ and Ca2+ ions as above, but also including either 3.0 mM Mg'+, 3.0 mM SI'+, or 30 mM Na+, growth improved, whereas 45Ca2+ accumulation was significantly decreased. Since most of the 45Ca2+ accumulated by roots during short-term treatments will reside in the apoplasm, these results indicate that displacement of Ca2+ from the apoplasm by AI cannot account for the AI-induced inhibition of root growth and, therefore, do not support the Ca2+-displacement hypothesis for AI toxicity. We also show that total accumulation of AI by root apices is greater in the AI-sensitive genotype than the AI-tolerant genotype and suggest that cation amelioration of AI toxicity is caused by the reduction in AI accumulation.Trivalent cations are generally harmful to plants. AI toxicity has attracted particular attention because its prevalence in acid soils can severely limit crop and pasture production. One of the first symptoms of stress is the inhibition of root growth, which can begin within hours or minutes, provided the root apex is directly exposed to A1 . A1 is known to affect many cellular functions, and determining which one of these interactions is the primary cause of toxicity continues to be an important goal (Haug, 1984; Haug and Caldwell, 1985;Taylor, 1988;Kochian, 1995). These investigations often require reliable estimates of AI uptake into the symplasm, but the capacity for the cell wall to accumulate high concentrations of cations makes the resolution of apoplasmic and symplasmic fractions difficult (Dainty and Hope, 1959; Zhang and Taylor, 1990; Reid and Smith, 1992). Some research indicates that A1 can readily cross the plasma membrane (Lazof et al., 1994) and that a large proportion of the A1 in roots resides in the symplasm (Tice et al., 1992; see Taylor,

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“…One of the reasons for this is the fact that aluminum is present in different ionic forms depending upon environmental conditions, mainly the pH of an aqueous solution, existing as Al(H 2 O) 6 3+ (abbreviated as Al 3+ ) at pH<4, as Al(OH) 2+ and Al(OH)2 + at pH 4 and above, as Al(OH)3 precipitates at neutral pH, and as Al(OH) 4 -in alkaline solution 11,27) . Based on the Al-pH chemistry, Al species in a medium below pH 3.5 presents predominantly as free Al 3+ ion, which is toxic to plants and microorganisms 25) .…”

Section: Discussionmentioning

confidence: 99%

“…These observations may suggest that the Al added functions to scavenge free organic acids produced from glucose, thereby protecting the organism from the growth-inhibiting effects of organic acids 17) and lowering the pH of medium. In this context, it is likely that solvated Al 3+ ions are hydrolyzed to form hydrated aluminum ions, simply expressed as [Al(H 2 O) 6-n (OH) n ] (3-n)+ , which behave as Bronsted acids in solution and can undergo acid-base reactions involving the transfer of a proton 11) .…”

Section: Discussionmentioning

confidence: 99%

Enhanced Growth of Acidocella facilis and Related Acidophilic Bacteria at High Concentrations of Aluminum.

et al. 2002

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Acidophilic chemoorganotrophic bacteria of the genus Acidocella, Acidiphilium, and Acidobacterium were tolerant to concentrations of monomeric aluminum ion (Al 3+ ) of up to 100 mM in an acid medium of pH 3.5 or less. Furthermore, their growth was remarkably enhanced by the presence of aluminum. The maximum amount of Al absorbed was 2.02 mg·g dry cell wt -1 for Acidocella facilis. Aluminum phosphate as well as aluminum sulfate among aluminum chemicals tested provided for the most luxuriant growth of this bacterium, whereas aluminum acetate and aluminum lactate had inhibitory effects on growth. The enhanced growth seemed to be caused by a chemical buffering action of the aluminum, but could not be explained merely by an alleviation of H + stress or by the scavenging of growth-inhibitory organic acids excreted. The reasons why the acidophiles are genuinely aluminophilic as well as aluminotolerant still remain to be elucidated. Considering that monomeric Al 3+ is dominant under strongly acid conditions, the possible cultivation of acidophiles at a pH below 4 affords a useful in vitro model system to probe the aluminum toxicity of plants as well as aluminum-microorganism interactions.

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Molecular aspects of aluminum toxicity

Cited by 329 publications

References 149 publications

Accumulation of Aluminium by Anabaena cylindrica into Polyphosphate Granules and Cell Walls: an X-ray Energy-dispersive Microanalysis Study

Accumulation of Aluminium by Anabaena cylindrica into Polyphosphate Granules and Cell Walls: an X-ray Energy-dispersive Microanalysis Study

Direct Evaluation of the Ca2+-Displacement Hypothesis for Al Toxicity

Enhanced Growth of Acidocella facilis and Related Acidophilic Bacteria at High Concentrations of Aluminum.

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