Overexpression of Arabidopsis phytochelatin synthase in tobacco plants enhances Cd2+ tolerance and accumulation but not translocation to the shoot
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Phytochelatins (PCs) are metal binding peptides involved in heavy metal detoxification. To assess whether enhanced phytochelatin synthesis would increase heavy metal tolerance and accumulation in plants, we overexpressed the Arabidopsis phytochelatin synthase gene (AtPCS1) in the non-accumulator plant Nicotiana tabacum. Wild-type plants and plants harbouring the Agrobacterium rhizogenes rolB oncogene were transformed with a 35S AtPCS1 construct. Root cultures from rolB plants could be easily established and we demonstrated here that they represent a reliable system to study heavy metal tolerance. Cd2+ tolerance in cultured rolB roots was increased as a result of overexpression of AtPCS1, and further enhanced when reduced glutathione (GSH, the substrate of PCS1) was added to the culture medium. Accordingly, HPLC analysis showed that total PC production in PCS1-overexpressing rolB roots was higher than in rolB roots in the presence of GSH. Overexpression of AtPCS1 in whole seedlings led to a twofold increase in Cd2+ accumulation in the roots and shoots of both rolB and wild-type seedlings. Similarly, a significant increase in Cd2+ accumulation linked to a higher production of PCs in both roots and shoots was observed in adult plants. However, the percentage of Cd2+ translocated to the shoots of seedlings and adult overexpressing plants was unaffected. We conclude that the increase in Cd2+ tolerance and accumulation of PCS1 overexpressing plants is directly related to the availability of GSH, while overexpression of phytochelatin synthase does not enhance long distance root-to-shoot Cd2+ transport.
KeywordsCd accumulation Cd tolerance Glutathione PCS1 overexpression Tobacco
Days after germination
Special thanks are given to Dr. Annette Pickford for helpful comments during manuscript revision. We thank Dr. Adele Figliolia (INP Rome, Italy) for helpful discussions, Prof. Rita Biasi and Dr. Patricia Gutierrez (University of Viterbo, Italy) for their help in ANOVA analysis. This work was partially supported by grants from Istituto Pasteur Fondazione Cenci-Bolognetti, and MIUR (FIRB, PRIN, Centro di Eccellenza in Biologia e Medicina Molecolare).
- Bellincampi D, Cardarelli M, Zaghi D, Serino G, Salvi G, Gatz C, Cervone F, Altamura MM, Costantino P, De Lorenzo G (1996) Oligogalacturonides prevent rhizogenesis in rolB-transformed tobacco explants by inhibiting auxin-induced expression of the rolB gene. Plant Cell 8:477–487PubMedCrossRefGoogle Scholar
- Papi M, Sabatini S, Bouchez D, Camilleri C, Costantino P, Vittorioso P (2000) Identification and disruption of an Arabidopsis zinc finger gene controlling seed germination. Genes Dev 1:28–33Google Scholar
- Sanitá di Toppi L, Lambardi M, Pecchioni N, Pazzagli L, Durante M, Gabrielli R (1999) Effects of cadmium stress on hairy roots of Daucus carota. J Plant Physiol 154:385–391Google Scholar
- Sanitá di Toppi L, Prasad MNV, Ottonello S (2002) Metal chelating peptides and proteins in plants. In: Prasad MNV, Strzaka K (eds) Physiology and biochemistry of heavy metal detoxification and tolerance in plants. Kluwer, Dordrecht, pp 59–93Google Scholar
- Vernoux T, Wilson RC, Seeley KA, Reichheld J, Muroy S, Brown S, Maughan SC, Cobbett CS, Van Montagu M, Inzè D, May MJ, Sung ZR (2000) The root meristemless1/cadmium sensitive2 gene defines a glutathione-dependent pathway involved in initiation and maintenance of cell division during postembryonic root development. Plant Cell 12:97–109PubMedCrossRefGoogle Scholar