[...]... Experimental Del Zaidin, CSIC, Granada 18008, Spain e-mail: guptadk1971@gmail.com D.K Gupta and L.M Sandalio (eds.), Metal Toxicity in Plants: Perception, Signaling and Remediation, DOI 10.1007/978-3-642-22081-4_1, # Springer-Verlag Berlin Heidelberg 2012 1 2 M Inouhe et al lesser toxic binding forms and hence affecting their movements, transports, accumulations and their final fates in vivo in plants PCs have... different sites of the plant body including their consolidate bindings to polymeric ligands in the structures are compared to facilitate our understanding on the possible roles of PCs and non-PC ligands contained in them 4 M Inouhe et al 2 Biological Ligands for Heavy Metal Conjugation and Detoxification in Plant Cells 2.1 Phytochelatins To protect themselves from the toxicity of metal ions, plant cells have... Fig 2 Possible metal localization and presence of major metal- binding ligands in a model plant with a standard root, stem and shoot system In each organ, tissues and cells are conventionally divided into apoplasic and symplastic sites The former including xylem (sap) in the conductive tissues of each organ, and rizosphere connected to or surrounding the root system underground, and also in some cases... in coordination and storage of phosphate and metals such as Zn, Mg, and K in vacuole and cytoplasm and also in the detoxification of Cd has been widely suggested (Van Steveninck et al 1992; Hayden and Cobbett 2006) Amino acids are the most abundant amphoteric ions with variable forms and residues, existing in 10–100 mM orders of concentrations and serving multiple functions in plant cells Cysteine (Cys)... amide group consisting of both O- and N-donors (ÀCO-NH2) All these are generally rich in phloem sap, for example, at near 300 mM in cereals and 50 mM in some dicotyledonous plants (Oshima et al 1990; Winter et al 1992), and can be potential ligands for translocational metal cations Histidine (His) is the most characterized imidazole (¼NH)-containing Heavy Metal Bindings and Their Interactions with Thiol... the organic ligand’s interactions with metals in each site at different but almost constant pH conditions (Callahan et al 2006) Some bindings between metals and ligands are not specific and not stable, especially under varied pH and ion-strength conditions Conversely the regulated conditions can promise a unique and established mechanism for metal transport and binding systems in land plants 2.3 Soluble... respective metals in plants (Fig 1) The tolerance characteristics of plants to heavy metal ions are diverse among the metal ions involved (Foy et al 1978; Woolhouse 1983; Verkleij and Schat 1990) Especially a group of metals called “Borderline class” metals including Mn, Zn, Fe, Ni, Cd, Pb and Cu etc are capable of binding to multiple types of naturally occurring chemicals or components in plants, although... detoxification than wall bindings 3.2 Distribution of Heavy Metals and Conjugating Ligands in Root Besides bioavailability, uptake and translocation efficiencies determine metal accumulation and distribution in plants (Clemens 2006) Roots are the plant organs in closest contact with metal- contaminated soils; therefore, they are the most affected by metals Resistance to excess metals can be achieved by... contain amounts of heavy metals Overexpression of cysteine synthase confers Cd tolerance to tobacco, and the endogenous concentration of Cd was 20% less in transgenic plants than in wild-type plants The numbers of both long and short trichomes in the transgenic plants were 25% higher than in that of wild-type plants, indicating the active excretion of Cd from trichomes in transgenic plants (Harada and. .. sites may allow more variable and more complicated interactions between the metal and biological ligands in plants This might be a potential for the differentiation and specification of a unique hyperaccumulator to be evolved on ground Readjustment of both the symplastic and apoplastic activities including the formations of PC-dependent and -independent metal- binding ligands and their transport systems . h1" alt="" Metal Toxicity in Plants: Perception, Signaling and Remediation . Dharmendra K. Gupta • Luisa M. Sandalio Editors Metal Toxicity in Plants: Perception, Signaling and Remediation Editors Dharmendra. Gupta and L.M. Sandalio (eds.), Metal Toxicity in Plants: Perception, Signaling and Remediation, DOI 10.1007/978-3-642-22081-4_1, # Springer-Verlag Berlin Heidelberg 2012 1 lesser toxic binding. metal detoxification and tolerance. Potential ligands include amino acids, nicotianamine, phytochelatins and metallothioneins (Clemens 2001). Phytochelatins have been the most widely studied in