title: Overexpression of Arabidopsis phytochelatin synthase in tobacco plants enhances Cd(2+) tolerance and accumulation but not translocation to the shoot.
abstract: 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. Cd(2+) 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 Cd(2+) accumulation in the roots and shoots of both rolB and wild-type seedlings. Similarly, a significant increase in Cd(2+) accumulation linked to a higher production of PCs in both roots and shoots was observed in adult plants. However, the percentage of Cd(2+) translocated to the shoots of seedlings and adult overexpressing plants was unaffected. We conclude that the increase in Cd(2+) 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 Cd(2+) transport.
authors.affiliation: Dipartimento di Genetica e Biologia Molecolare, Universitá La Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy.
authors.forename: Mirella
authors.initials: M
authors.lastname: Pomponi
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Censi
authors.forename: Valentina
authors.initials: V
authors.lastname: Di Girolamo
authors.forename: Angelo
authors.initials: A
authors.lastname: De Paolis
authors.forename: Luigi Sanità
authors.initials: LS
authors.lastname: di Toppi
authors.forename: Rita
authors.initials: R
authors.lastname: Aromolo
authors.forename: Paolo
authors.initials: P
authors.lastname: Costantino
authors.forename: Maura
authors.initials: M
authors.lastname: Cardarelli
mesh_terms: D019881:Aminoacyltransferases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics; D001692:Biological Transport; D002104:Cadmium / Q000378:metabolism*; D003001:Cloning, Molecular; D003470:Culture Media; D018506:Gene Expression Regulation, Plant; D005978:Glutathione / Q000096:biosynthesis / Q000494:pharmacology; D054811:Phytochelatins; D018517:Plant Roots / Q000201:enzymology / Q000502:physiology; D018520:Plant Shoots / Q000201:enzymology / Q000502:physiology; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D014026:Nicotiana / Q000033:anatomy & histology / Q000235:genetics* / Q000378:metabolism; D001617:beta-Glucosidase / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D003470:Culture Media; D002104:Cadmium; D054811:Phytochelatins; D019881:Aminoacyltransferases; C502365:AT5G44070 protein, Arabidopsis; C092241:RolB protein, Agrobacterium rhizogenes; D001617:beta-Glucosidase; D005978:Glutathione