Glutathione and a UV light-induced glutathione S-transferase are involved in signaling to chalcone synthase in cell cultures

UV irradiation stimulates expression of the gene encoding the key enzyme ch alcone synthase (CHS), which leads to the generation of protective flavonoi ds in parsley cell cultures. CHS transcripts increase after 3 to 4 hr, and early genes are involved in the signal transduction to the CHS promoter. By using the fluorescent differential display technique in a large-scale scre ening, several early UV light-induced genes were isolated. Of these, a nove l glutathione S-transferase (PcGST1) is induced within 2 hr and precedes CH S expression. Overexpression of PcGST1 in transformed cell lines containing a CHS promoter/luciferase reporter (CHS-LUC) affected the onset of LUC tra nscription. Supplementing these cell lines with glutathione immediately sti mulated CHS-LOC expression within 2 hr in dark-incubated cells and resulted in a biphasic induction profile in UV-irradiated cells. Our data indicate the involvement of glutathione and PcGST1 in early events of a UV light-dep endent signal transduction pathway to CHS. In this context, the oxidative s tatus of a cell acts as a central regulating element.