Heavy metal tolerance and accumulation in Indian mustard (Brassica juncea L.) expressing bacterial gamma-glutamylcysteine synthetase or glutathione synthetase.
The overexpression of either gamma-glutamylcysteine synthetase (gamma-ECS) or glutathione synthetase (GS) in Brassica juncea transgenics was shown previously to result in higher accumulation of glutathione (GSH) and phytochelatins (PCs), as well as enhanced Cd tolerance and accumulation. The present study was aimed at analyzing the effects of gamma-ECS or GS overexpression on tolerance to and accumulation of other metal/loids supplied individually in agar medium (seedlings) or in hydroponics (mature plants). Also, as pollution in nature generally consists of mixtures of metals, glutamylcysteine synthetase (ECS) and GS seedlings were tested on combinations of metals. Compared to wild-type plants, ECS and GS transgenics exhibited a significantly higher capacity to tolerate and accumulate a variety of metal/loids (particularly As, Cd, and Cr) as well as mixed-metal combinations (As, Cd, Zn/As, Pb, and Zn). This enhanced metal tolerance and accumulation of the ECS and GS transgenics may be attributable to enhanced production of PCs, sustained by a greater availability of GSH as substrate, as suggested by their higher concentrations of GSH, PC2, PC3, and PC4 as compared to wild-type plants. Overexpression of GS and gamma-ECS may represent a promising strategy for the development of plants with an enhanced phytoremediation capacity for mixtures of metals.
Reisinger
Sarah
S
Department of Plant and Microbial Biology, University of California, Berkeley, California, USA.
Schiavon
Michela
M
Terry
Norman
N
Pilon-Smits
Elizabeth A H
EA
D001673:Biodegradation, Environmental; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D005981:Glutathione Synthase / Q000235:genetics / Q000378:metabolism*; D019216:Metals, Heavy / Q000378:metabolism / Q000633:toxicity*; D009149:Mustard Plant / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D054811:Phytochelatins / Q000378:metabolism; D018517:Plant Roots; D030821:Plants, Genetically Modified
D019216:Metals, Heavy; D054811:Phytochelatins; D005721:Glutamate-Cysteine Ligase; D005981:Glutathione Synthase; D005978:Glutathione