Subcellular localization of cadmium in roots and leaves of Arabidopsis thaliana

Abstract

Summary• We examined the subcellular cadmium (Cd) localization in roots and leaves of wild-type Arabidopsis thaliana (ecotype Columbia) exposed to environmentally relevant Cd concentrations.• Energy-dispersive X-ray microanalysis (EDXMA) was performed on high-pressure frozen and freeze-substituted tissues.• In the root cortex, Cd was associated with phosphorus (Cd/P) in the apoplast and sulfur (Cd/S) in the symplast, suggesting phosphate and phytochelatin sequestration, respectively. In the endodermis, sequestration of Cd/S was present as fine granular deposits in the vacuole and as large granular deposits in the cytoplasm. In the central cylinder, symplastic accumulation followed a distinct pattern illustrating the importance of passage cells for the uptake of Cd. In the apoplast, a shift of Cd/S granular deposits from the middle lamella towards the plasmalemma was observed. Large amounts of precipitated Cd in the phloem suggest retranslocation from the shoot. In leaves, Cd was detected in tracheids but not in the mesophyll tissue.• Extensive symplastic and apoplastic sequestration in the root parenchyma combined with retranslocation via the phloem confirms the excluder strategy of Arabidopsis thaliana .

Examining the Specific Contributions of Individual Arabidopsis Metallothioneins to Copper Distribution and Metal Tolerance

“…In the absence of PCs, MT1a and MT2b may participate in transport or sequestration of Cd in the phloem. This hypothesis is supported by a recent report that Cd accumulates in the phloem of Arabidopsis plants and that translocation of Cd from mesophyll cells to phloem may constitute an important mechanism for Cd tolerance in Arabidopsis (Belleghem et al, 2007). PCs may also have a role in the transport of Cu in the xylem or phloem tissues.…”

Pb and Cd on growth, leaf ultrastructure and essential oil yield mint (Mentha arvensis L.)

“…Granules with electron dense content around chloroplasts and nucleus of M. arvensis mesophyll cells treated with Cd, and around M. arvensis mitochondria of mesophyll cells treated with Pb, were previously observed in Aradopsis thaliana roots under high concentrations of Cd (BELLENGHEM et al, 2007) and Zea mays roots treated with Pb (TUNG & TEMPLE, 1996). These structures were described as granular deposits present in the cortex intercellular spaces or in the cell wall.…”

“…These structures were described as granular deposits present in the cortex intercellular spaces or in the cell wall. The metal would be transported from the apoplast to the symplast, reducing its movement in the plant (TUNG & TEMPLE, 1996;BELLENGHEM et al, 2007).…”

Elemental distribution by cryo-micro-PIXE in the zinc and cadmium hyperaccumulator Sedum plumbizincicola grown naturally

“…A high Zn concentration in the xylem indicates efficient vertical transport via the xylem. Nevertheless, similar to many other species such as N. praecox (Vogel-Mikuš et al 2008a), Arabidopsis thaliana (Belleghem et al 2007) and S. alfredii (Tian et al 2009), considerable accumulation of Zn in the phloem of S. plumbizincicola suggests a strong translocation of this metal from shoots to other tissues. Moreover, in the stem of S. plumbizincicola the Zn concentration in the parenchyma surrounding the xylem indicates transverse transport of this element.…”