Glutathione and a UV Light–Induced Glutathione S-Transferase Are Involved in Signaling to Chalcone Synthase in Cell Cultures

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Abstract
UV irradiation stimulates expression of the gene encoding the key enzyme chalcone synthase (CHS), which leads to the generation of protective flavonoids 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 screening, several early UV light-induced genes were isolated. Of these, a novel glutathione S-transferase (PcGST1) is induced within 2 hr and precedes CHS expression. Overexpression of PcGST1 in transformed cell lines containing a CHS promoter/luciferase reporter (CHS-LUC) affected the onset of LUC transcription. Supplementing these cell lines with glutathione immediately stimulated CHS-LUC 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-dependent signal transduction pathway to CHS. In this context, the oxidative status of a cell acts as a central regulating element.