Molecular characterization of phytochelatin synthase expression in transgenic Arabidopsis

Promoter activities regulating a phytochelatin synthase gene were characterized in transgenic Arabidopsis thaliana (ecotype Columbia 0). Histochemical localization analysis of β-glucuronidase (GUS) activity in transgenic lines containing a 2.0 kb AtPCS1 (A. thaliana phytochelatin synthase) promoter fused to a uid A gene construct detected GUS activities in leaves, roots, cotyledons, and stems, but not in root tips or root hairs throughout all stages of plant development. Of particular interest, a strong GUS activity was detected in leaf trichomes. During flowering, GUS activity was not detected in either petals or stamens, but was present in sepals, carpels, and elongating seedpods. The GUS activities in seedpods gradually decreased during their development, but remained in both base- and tip-ends as seedpods matured to siliques. These GUS activities correlated well with AtPCS1 protein levels as observed in western blot analysis of transgenic plants containing the 2.0 kb AtPCS1 promoter fused to a FLAG-tagged AtPCS1 genomic DNA construct. AtPCS1 was not post-transcriptionally regulated by cadmium (Cd). However, by comparing transgenic plants containing the 2.0 kb AtPCS1 promoter fused to either AtPCS1 cDNA or AtPCS1 genomic DNA, it was observed that intron(s) mediated enhancement of mRNA accumulation. Overexpression of AtPCS1 was observed in transgenic plants containing the 2.0 kb AtPCS1 promoter fused to genomic AtPCS1 DNA.