Overexpression of Arabidopsis phytochelatin synthase in tobacco plants enhances Cd2+ 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.

Zinc-Finger Transcription Factor ZAT6 Positively Regulates Cadmium Tolerance through the Glutathione-Dependent Pathway in Arabidopsis

“…Furthermore, overexpression of GSH1, PCS1, or PCS2 is effective in improving plant tolerance upon Cd stress (Zhu et al, 1999;Cazalé and Clemens, 2001;Pomponi et al, 2006;Gasic and Korban, 2007;Brunetti et al, 2011), and simultaneous expression of PC synthesis genes leads to higher Cd accumulation and tolerance (Wawrzynski et al, 2006). In our study, we found that ZAT6 functions in Cd accumulation and tolerance, and up-regulation of ZAT6 leads to elevated expressions of GSH1, GSH2, PCS1, and PCS2 (Fig.…”

Cadmium uptake kinetics and plants factors of shoot Cd concentration

“…Shoot Cd concentrations at 15 % growth reduction measured in this experiment are higher than the phytotoxicity thresholds between 14 and 19 mgkg −1 as reported for sunflower (Gopal and Nautiyal 2011). Tolerance to internal Cd concentration is probably related to differences in the detoxification of Cd in the cell brought about by vacuolar compartmentation and binding to cell walls (Vogel-Mikus et al 2010) or by reaction with endogenous phytochelatins and GSH (Brunetti et al 2011;Pomponi et al 2006). …”

The symbiosis between Nicotiana tabacum and the endomycorrhizal fungus Funneliformis mosseae increases the plant glutathione level and decreases leaf cadmium and root arsenic contents

“…Studies on As detoxification by means of PCs or other mechanisms are scarce in this species (Wojas et al, 2010a). Conversely, the synthesis of PCs in tobacco seedlings and young plants, after treatment with Cd, has been demonstrated (Nicotiana rustica: V€ ogeli-Lange and Wagner, 1990Wagner, , 1996; N. tabacum: Krystofova et al, 2012;Pomponi et al, 2006;Wojas et al, 2008Wojas et al, , 2010b, alongside their ability to promptly detoxify this metal.…”