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GrainGenes Reference Report: EEB-49-21

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Reference	EEB-49-21
Title	Phytochelatin and cadmium accumulation in wheat
Journal	Environmental and Experimental Botany
Year	2003
Volume	49
Pages	21-28
Author	Stolt JP Sneller FEC Bryngelsson T Lundborg T Schat H
Abstract	Summary: Cadmium (Cd) is a nonessential heavy metal that can be harmful at low concentrations in organisms. Therefore, it is necessary to decrease Cd accumulation in the grains of wheats aimed for human consumption. In response to Cd, higher plants synthesize sulphur-rich peptides, phytochelatins (PCs). PC-heavy metal complexes have been reported to accumulate in the vacuole. Retention of Cd in the root cell vacuoles might influence the symplastic radial Cd transport to the xylem and further transport to the shoot, resulting in genotypic differences in grain Cd accumulation. We have studied PC accumulation in 12-day-old seedlings of two cultivars of spring bread wheat (Triticum aestivum), and two spring durum wheat cultivars (Triticum turgidum var. durum) with different degrees of Cd accumulation in the grains. Shoots and roots were analysed for dry weight, Cd and PC accumulation. There were no significant differences between the species or the varieties in the growth response to Cd, nor in the distributions of PC chain lengths or PC isoforms. At 1 micromolar external Cd, durum wheat had a higher total Cd uptake than bread wheat, however, the shoot-to-root Cd concentration ratio was higher in bread wheat. When comparing varieties within a species, the high grain Cd accumulators exhibited lower rates of root Cd accumulation, shoot Cd accumulation, and root PC accumulation, but higher shoot-to-root Cd concentration ratios. Intraspecific variation in grain Cd accumulation is apparently not only explained by differential Cd accumulation as such, but rather by a differential plant-internal Cd allocation pattern. However, the higher average grain Cd accumulation in the durum wheats, as compared to the bread wheats, is associated with a higher total Cd accumulation in the plant, rather than with differential plant-internal Cd allocation. The root-internal PC chain length distributions and PC-thiol-to-Cd molar ratios did not significantly differ between species or varieties, suggesting that differential grain Cd accumulation is not due to differential PC-based Cd sequestration in the roots
Keyword	[ Hide all but 1 of 44 ] allocation arabidopsis biosynthesis bread bread wheat cadmium cd cell chain-length complexes concentration consumption difference durum genetic variation glutathione grains growth growth-response heavy metal human intraspecific variation isoform maize metal-binding peptides organisms pattern phytochelatin phytochelatin isoforms phytochelatins rate ratios seedling sequestration spring synthase tolerant silene vulgaris translocation transport triticum triticum aestivum triticum turgidum uptake xylem

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