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  • 1
    Electronic Resource
    Electronic Resource
    Aluminium tolerance is achieved by exudation of citric acid from roots of soybean (Glycine max) (2000)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 110 (2000), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Fourteen soybean (Glycine max [L.] Merr.) cultivars were analysed and found to differ considerably in aluminium (Al) resistance. The cultivars Suzunari (Al-resistant) and Shishio (Al-sensitive) were selected for further analysis of physiological mechanisms of Al-resistance. The relative root growth of Shishio was 48% compared to 76% for Suzunari in response to 15 μM Al (24 h). Aluminium accumulation and Al-induced callose formation in root apices were 50 and 25% of that in Suzunari, respectively. Al inhibited both Suzunari and Shishio during the first 6 h of exposure. However, the root growth inhibition was further increased in Shishio but not in Suzunari, suggesting an Al-induced Al-resistant mechanism operating in Suzunari. Organic acid analysis in root exudates of both cultivars revealed that they specifically exuded citrate in response to Al. However, the citrate exudation rate was significantly higher in Suzunari during the 6 h/24 h Al treatment, which was 52/330 compared to Shishio's 26/118 (nmol [g root fresh weight]−1 [6 h]−1), respectively. This Al-induced citric acid exudation was found to be specific for Al, as several other metals failed to induce citrate exudation in both cultivars. Fourteen days of P deficiency did not elicit citrate excretion in both cultivars, while application of Al to P-deficient plants rapidly induced citrate exudation in both cultivars, confirming the specificity of the response of these soybean cultivars to Al. To our knowledge, this is the first report demonstrating an Al-exclusion mechanism in soybean cultivars, which is conferred by enhanced and specific Al-induced exudation of citrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2000.110110.x
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of aluminium-induced citrate secretion in aluminium-tolerant soybean (Glycine max) plants (2001)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 113 (2001), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Recently, we showed that secretion of citrate in an aluminium (Al) tolerant cultivar soybean (Glycine max) (cv. Suzunari) is a specific response to Al stress [Yang et al. (2000) Physiol Plant 110: 72–77]. Here we investigated the intrinsic mechanisms behind the secretion of citrate induced by Al. The amount of citrate secreted during the 24-h Al treatment period increased with increasing concentration of Al (0–70 μM). We analysed citrate secretion basically under 3 conditions: (1) by varying light-exposure, (2) with intact or excised shoots and (3) by using a divided chamber technique. Further, the content of organic acids in the tissue and the activity of enzymes involved in organic acid metabolism were analysed and evaluated. The results indicate that high rate of citrate secretion in soybean requires a 4-h induction period. Al had a continuous effect on the citrate secretion when Al was removed from the treatment solution. Citrate secretion increased steadily under exposure to continuous light. However, when the shoots were excised the citrate secretion rate dropped to 3–6 times that of their control counterparts. Results of root manipulation experiments revealed that citrate secretion required the direct contact of Al. In other words, only the Al-treated root portions secreted citrate. All these observations suggest that the shoots play a role in Al-induced citrate secretion. Although shoots may not supply citrate for the secretion upon Al treatment, it seems that they may provide the carbon source and/or energy for citrate synthesis in the root. On the other hand, the root organic acid content (1-cm apex) indicated that malate might contribute to citrate secretion by keeping the balance between citrate synthesis and release in the root apices. Quantification of enzymes involved in organic acid metabolism showed only a 16% increase in citrate synthase activity upon Al treatments (6 h) with no differences in other enzymes. Hence, we could not rule out completely the potential contribution of citrate from shoots and the results are discussed in the light of shoots contributing either energy or citrate itself for enhanced citrate secretion in the Al-tolerant plant roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2001.1130109.x
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  • 3
    Electronic Resource
    Electronic Resource
    Compartmentalization of S-RNase and HT-B degradation in self-incompatible Nicotiana (2006)
    [s.l.] : Nature Publishing Group
    Nature 439 (2006), S. 805-810 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Pollen–pistil interactions are crucial for controlling plant mating. For example, S-RNase-based self-incompatibility prevents inbreeding in diverse angiosperm species. S-RNases are thought to function as specific cytotoxins that inhibit pollen that has an S-haplotype that matches ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature04491
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  • 4
    Electronic Resource
    Electronic Resource
    Acquisition of aluminum tolerance in Saccharomyces cerevisiae by expression of the BCB or NtGDI1 gene derived from plants (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 171 (1999), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Eleven aluminum stress-induced genes derived from plants (wheat, Arabidopsis and tobacco) were introduced into Saccharomyces cerevisiae to test if expression of these genes confers Al tolerance. Al sensitivity tests showed that expression of two genes, either an Arabidopsis gene for blue copper binding protein (BCB), or a tobacco gene for the GDP dissociation inhibitor (NtGDI1), conferred Al tolerance. Determinations of total content and localization of Al ions in these transformants suggested that the BCB gene product functions in restricting Al uptake, while expression of the NtGDI1 gene promotes release of Al ions after uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1999.tb13415.x
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  • 5
    Electronic Resource
    Electronic Resource
    Differential impacts of aluminium on microtubule organisation depends on growth phase in suspension-cultured tobacco cells (1999)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 107 (1999), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We investigated the impacts of aluminium (Al) on the structural organisation of microtubules (MTs) in suspension-cultured tobacco (Nicotiana tabacum L. cv. Samsun) cells using monoclonal anti-tubulin antibodies coupled with confocal microscopy. Cells were treated with Al (50 μM) in a simple calcium solution (3 mM CaCl2 and 3% [w/v] sucrose, pH 4.5) up to 24 h. The impacts of Al on tobacco cells were found to be distinct, depending on the growth phase of cells. Cells at logarithmic (log) phase lost their structural integrity of phragmoplasts and spindle MTs during Al treatments. In log-phase cells, the cortical microtubules (CMTs) showed no visible changes in the initial 1 h, but progressive alteration, such as less prominent (after 6 h) and intensive (from 12 h onwards) depolymerisation of MTs, was registered upon increasing Al treatment duration, which accompanied Al-induced callose formation. The growth of log-phase cells showed a tendency of inhibition between 6 and 12 h Al treatment, which led to significant growth inhibition from 12 h onwards, suggesting that Al-induced depolymerisation of CMTs in log-phase cells is closely linked to the Al-induced inhibition of cell growth. In contrast, Al-induced stabilisation of CMTs was found in stationary-phase cells and these cells required higher Al levels (100 μM) for the depolymerisation of CMTs. These results provide first circumstantial evidence for both depolymerisation and stabilisation of MTs induced by Al, depending on the phases of plant cell growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1999.100115.x
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  • 6
    Electronic Resource
    Electronic Resource
    Does aluminium affect root growth of maize through interaction with the cell wall – plasma membrane – cytoskeleton continuum? (1999)
    Springer
    Plant and soil 215 (1999), S. 163-174 
    Details
    ISSN: 1573-5036
    Keywords: al resistance ; al toxicity ; apoplast ; cell wall ; cytoskeleton ; pectin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The mechanism of aluminium-induced inhibition of root elongation is still not well understood. It is a matter of debate whether the primary lesions of Al toxicity are apoplastic or symplastic. The present paper summarises experimental evidence which offers new avenues in the understanding of Al toxicity and resistance in maize. Application of Al for 1 h to individual 1 mm sections of the root apex only inhibited root elongation if applied to the first 3 apical mm. The most Al-sensitive apical root zone appeared to be the 1–2 mm segment. Aluminium-induced prominent alterations in both the microtubular (disintegration) and the actin cytoskeleton (altered polymerisation patterns) were found especially in the apical 1–2 mm zone using monoclonal antibodies. Since accumulation of Al in the root apoplast is dependent on the properties of the pectic matrix, we investigated whether Al uptake and toxicity could be modulated by changing the pectin content of the cell walls through pre-treatment of intact maize plants with 150 mM NaCl for 5 days. NaCl-adapted plants with higher pectin content accumulated more Al in their root apices and they were more Al-sensitive as indicated by more severe inhibition of root elongation and enhanced callose induction by Al. This special role of the pectic matrix of the cell walls in the modulation of Al toxicity is also indicated by a close positive correlation between pectin, Al, and Al-induced callose contents of 1 mm root segments along the 5 mm root apex. On the basis of the presented data we suggest that the rapid disorganisation of the cytoskeleton leading to root growth inhibition may be mediated by interaction of Al with the apoplastic side of the cell wall – plasma membrane – cytoskeleton continuum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004439725283
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