The effect of the heterologous expression of Phragmites australis gamma-glutamylcysteine synthetase on the Cd2+ accumulation of Agrostis palustris.

Heavy metal pollution has become one of the most serious environmental problems today. To develop a more efficient plant to clean up heavy metal contaminated soils, a gamma-glutamylcysteine synthetase (GCS) cDNA, named PaGCS, was isolated by PCR from Phragmites australis. The PaGCS sequence was transformed via agroinfection into the heavy metal intolerant grass Agrostis palustris. Five confirmed transgenic A. palustris plants expressing PaGCS were compared with the wild-type line for growth and Cd(2+) accumulation, as well as for the expression of a number of phytochelatin synthesis and stress-responsive enzymes when challenged with Cd(2+) stress. GCS and phytochelatin synthase (PCS) were up-regulated in the transgenic lines. All the transgenic lines accumulated more Cd(2+) and phytochelatins (PCs) than the wild-type line, and three of the five lines grew more effectively than the wild-type after either five or 21 d of Cd(2+) stress. Variation among the transgenics was observed for the distribution of Cd(2+) in the root, shoot and leaf. The malondialdehyde content of all the transgenic lines was lower than that of the wild type under Cd(2+) treatment, while the activity of both superoxide dismutase and peroxidase present in the transgenic lines increased markedly 24 h after Cd(2+) stress, and then rapidly declined.