Relationships between Cadmium, Zinc, Cd-Peptide, and Organic Acid in Tobacco Suspension Cells

Krotz, R.M.; Evangelou, Bill P.; Wagner, George J.

doi:10.1104/pp.91.2.780

Cited by 144 publications

(69 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Earlier, Krotz et al (9) showed that after 3 to 4 d exposure of Datura cultured cells to 30 to 45 AM Cd most of the metal was recovered in isolated vacuoles. A number of studies using electron microscopy techniques have shown the presence of Cd deposits in vacuoles as well as other sites within tissues of plants exposed to high levels of Cd (5,19,25,26).…”

Section: Methodsmentioning

confidence: 97%

“…The study was carried out using a computer model, GEO-CHEM-PC (16,23), to simulate the chemical thermodynamic state of the vacuole based principally on chemical data of vacuole content of tobacco suspension cells (9). The GEO-CHEM-PC computer model uses an iterative procedure to solve simultaneously all equations describing dissolved and solid species.…”

Section: Methodsmentioning

confidence: 99%

“…Its features have been described in detail elsewhere (16 Tables II and III, and the thermodynamic protonation constants for various ligands are listed in Table IV. Concentrations of organic acids and ions were estimated from extracts of Cd-treated cultured cell assuming that 75% of packed cell volume was vacuolar sap and that major ion and organic acid species occur in the vacuole in vivo (9). The last assumption (for acids and nutrient ions) is based on earlier 10 and 30% ofCd present was as Cd-peptide, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…Recent studies suggest that heavy metals accumulated in the higher plant are mainly compartmentalized in the vacuole (5,7,9,27). Various mechanisms have been proposed to account for the accumulation of these potentially toxic heavy metal ions in the plant vacuole (18,30).…”

mentioning

confidence: 99%

“…Various mechanisms have been proposed to account for the accumulation of these potentially toxic heavy metal ions in the plant vacuole (18,30). In general, these mechanisms include formation of soluble metal-organic acid complexes (4,9,14) or metal-phytate (25,26), formation ofmetalpeptide or metal-peptide-sulfide complexes (9,18,27), or precipitation of metal-sulfides (2,21,25).…”

mentioning

confidence: 99%

See 4 more Smart Citations

Computer-Simulated Evaluation of Possible Mechanisms for Quenching Heavy Metal Ion Activity in Plant Vacuoles

Wang¹,

Evangelou²,

Nielsen³

et al. 1991

Plant Physiol.

Self Cite

View full text Add to dashboard Cite

Various mechanisms have been suggested for the quenching of Cd ion activity in plant vacuoles. These include solution complexation with organic acids and sulfhydryl-containing peptides and precipitation as sulfides. Because direct experimental support for these mechanisms is lacking and difficult to obtain, we have used a computer model to evaluate the quenching role of possible organic and inorganic ligands of tobacco cultured cells exposed to Cd. Results of this thermodynamic evaluation, which assumes that a chemical equilibrium state is met in the vacuole, support the conclusion that sulfhydryl-containing peptides and certain organic acids may form soluble Cd complexes. Although complexation of malate and oxalate with Cd is predicted to be less significant, citrate in the concentration range encountered in the tobacco cultured cell vacuoles has high potential for forming soluble complexes with Cd over the entire possible vacuolar pH range, especially 4.3 to 7.0, even in the presence of low levels of Cd-binding peptides. In addition, results show that inorganic chloride, sulfide (if present), and phosphate may also act to sequester Cd ion activity in the vacuole by forming soluble Cd-Cl and insoluble CdS and Cd-phosphate.Understanding the fate ofCd in plants is of interest because of concerns of Cd transfer from plants to animals and man. Recent studies suggest that heavy metals accumulated in the higher plant are mainly compartmentalized in the vacuole (5, 7, 9, 27). Various mechanisms have been proposed to account for the accumulation of these potentially toxic heavy metal ions in the plant vacuole (18,30). In general, these mechanisms include formation of soluble metal-organic acid complexes (4, 9, 14) or metal-phytate (25, 26), formation ofmetalpeptide or metal-peptide-sulfide complexes (9, 18, 27), or precipitation of metal-sulfides (2,21,25).Support for a particular mechanism of accumulation/sequestration of an ion is gained if the compartment of accumulation/sequestration is verified and if speciation of the ion in that compartment is determined. Both direct and indirect approaches (10) used to determine compartmentation ofions, including heavy metals, can only provide qualitative and quantitative estimates of vacuole contents (28). They cannot identify the species of ion complexes occurring in vacuoles. Therefore, mechanisms proposed on the basis of compartmentation analysis alone are not sufficient to argue the validity of a mechanism of accumulation/sequestration. However, it is possible with computer assistance to simulate the ion species distribution in the plant vacuole and thus to evaluate a proposed mechanism.Computer calculations have been used to model the chemistry of xylem sap of soybean and tomato (29). Here, we use data obtained previously regarding sap composition of vacuoles from Cd-treated tobacco (Nicotiana tabacum) cultured cells and the GEOCHEM-PC computer model (16,23) to predict ion species of these vacuoles in vivo. The prediction of ion speciation in vacuoles of Zn-treate...

show abstract

Section: Methodsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Computer-Simulated Evaluation of Possible Mechanisms for Quenching Heavy Metal Ion Activity in Plant Vacuoles

Wang¹,

Evangelou²,

Nielsen³

et al. 1991

Plant Physiol.

Self Cite

View full text Add to dashboard Cite

show abstract

Genotypic differences in uptake and translocation of cadmium in bean and maize inbred lines

Guo

Marschner

1996

J Plant Nutrition & Soil

View full text Add to dashboard Cite

For better understanding of mechanisms responsible for genotypic differences in uptake and translocation of cadmium (Cd) in different plant species, two maize (Zea mays L.) inbred lines (B37 and F2) and a bean (Phaseolus vulgaris L.) cultivar (Saxa) were grown in a complete nutrient solution with additional 0.5 μM Cd and 250 μM buthionine sulfoximine (BSO), an inhibitor of PC synthesis, alone or in combination. The maize line B37 had a much higher Cd content in shoots (116.2 mg Cd kg−1 dry wt.) than F2 (32.7 mg Cd kg−1 dry wt.) and bean (1.83 in leaves, and 2.85 mg Cd kg−1 dry wt. in stems), whereas in roots the Cd content was much higher in bean (602.6 mg Cd kg−1 dry wt.) than in maize (427.1 mg Cd kg−1 dry wt. in B37, and 428.2 mg Cd kg−1 dry wt. in F2). Application of BSO markedly decreased Cd contents in roots of bean and maize lines, and also Cd contents in shoots and stem basis of both maize lines, while Cd contents in leaves, stems and stem basis of bean were not reduced by BSO.In root extracts (Tris‐HCl buffer, pH 8.0) the proportion of Cd in the soluble fraction was much lower in bean (29.6%) than in the maize lines B37 (58.6%) and F2 (60.1%). Compared with the whole root tissue, Cd contents in the stele of the roots were much lower, especially in bean, and decreased by BSO in both maize lines, but not in bean.Gel‐chromatography of root extracts strongly suggested that in the soluble fraction about 80% of the Cd was present as Cd‐phytochelatin (PC) complexes in B37, whereas in F2 this Cd fraction accounted for about 50%, and in bean only for a few percent in the soluble fraction, Our results suggest that Cd‐PC complexes constitute a mobile form in plants. The lower proportion of Cd in the soluble fraction as well as lower PC production in roots of bean compared to maize lines may be the main reasons for the very low Cd translocation from roots to shoots in bean plants.

show abstract

Effects of cadmium amendments on low-molecular-weight organic acid exudates in rhizosphere soils of tobacco and sunflower

et al. 2006

View full text Add to dashboard Cite

To recognize physiological response of plants to cadmium (Cd) toxicity in rhizosphere of plants, the pot experiments were employed to investigate how low-molecular-weight organic acids (LMWOAs) were exudated from tobacco and sunflower roots of Cd-amended soils. The aims of this study were to assess the effect of LMWOAs on uptake of Cd by tobacco and sunflower under pot experiments, thus comparing the ability of tobacco and sunflower for phytoremediation. Surface soils (0-20 cm) were collected from Taichung Experiment Station (TC) (silty loam). Cadmium chloride (CdCl(2)) was amended into TC soil, giving Cd concentrations of 1, 5, 10 mg kg(-1) soil. Soils with different concentrations of Cd were put into 12 cm (i.d.) pots for incubation, and then 2-week-old tobacco and sunflower seedlings were transplanted into the pots. Tobacco and sunflower were grown in greenhouse for 50 days, respectively. The rhizosphere and bulk soils, and fresh plant tissues were collected after harvest. The Cd concentrations in the plant and transfer factor values in the sunflower were higher than that in the tobacco. No LMWOAs were detected by gas chromatograph in bulk soils, and low amounts of LMWOAs were found in uncontaminated rhizosphere soils. Acetic, lactic, glycolic, malic, maleic, and succinic acids were found in the tobacco and sunflower rhizosphere soils. Concentrations of LMWOAs increased with increasing amendment of Cd concentrations in tobacco and sunflower rhizosphere soils. Correlation coefficient (r) of concentrations of Cd amendment versus LMWOAs exudates of tobacco and sunflower were 0.85 and 0.98, respectively. These results suggest that the different levels of LMWOAs present in the rhizosphere soil play an important role in the solubilization of Cd that bound with soil particle into soil solution and then uptake by plants.

show abstract

Relationships between Cadmium, Zinc, Cd-Peptide, and Organic Acid in Tobacco Suspension Cells

Cited by 144 publications

References 22 publications

Computer-Simulated Evaluation of Possible Mechanisms for Quenching Heavy Metal Ion Activity in Plant Vacuoles

Computer-Simulated Evaluation of Possible Mechanisms for Quenching Heavy Metal Ion Activity in Plant Vacuoles

Genotypic differences in uptake and translocation of cadmium in bean and maize inbred lines

Effects of cadmium amendments on low-molecular-weight organic acid exudates in rhizosphere soils of tobacco and sunflower

Contact Info

Product

Resources

About