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Cadmium Tolerance and Accumulation in Indian Mustard Is Enhanced by Overexpressing γ-Glutamylcysteine Synthetase
Yong Liang Zhu, Elizabeth A. H. Pilon-Smits, Alice S. Tarun, Stefan U. Weber, Lise Jouanin and Norman Terry
Vol. 121, No. 4 (Dec., 1999), pp. 1169-1177
Published by: American Society of Plant Biologists (ASPB)
Stable URL: http://www.jstor.org/stable/4279044
Page Count: 9
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To investigate rate-limiting factors for glutathione and phytochelatin (PC) production and the importance of these compounds for heavy metal tolerance, Indian mustard (Brassica juncea) was genetically engineered to overexpress the Escherichia coli gshl gene encoding γ-glutamylcysteine synthetase (γ-ECS), targeted to the plastids. The γ-ECS transgenic seedlings showed increased tolerance to Cd and had higher concentrations of PCs, γ-GluCys, glutathione, and total non-protein thiols compared with wild-type (WT) seedlings. When tested in a hydroponic system, γ-ECS mature plants accumulated more Cd than WT plants: shoot Cd concentrations were 40% to 90% higher. In spite of their higher tissue Cd concentration, the γ-ECS plants grew better in the presence of Cd than WT. We conclude that overexpression of γ-ECS increases biosynthesis of glutathione and PCs, which in turn enhances Cd tolerance and accumulation. Thus, overexpression of γ-ECS appears to be a promising strategy for the production of plants with superior heavy metal phytoremediation capacity.
Plant Physiology © 1999 American Society of Plant Biologists (ASPB)