Action spectrum for induction of promoter activity of phenylalanine ammonia-lyase gene by UV in carrot suspension cells.

The full-length promoter (-2335) of the carrot (Daucus carota) phenylalanine ammonia-lyase gene (gDcPAL1) fused to the luciferase reporter gene was transiently transformed to carrot protoplasts by electroporation, and the promoter activity induced by monochromatic UV light of various wavelengths was examined. The action spectrum constructed from the fluence-response curves showed a single peak at around 280 nm, suggesting that the activation of the gDcPAL1 promoter is categorizable as one of the UVB light responses. The same assay system was applied to variously truncated gDcPAL1 promoters and to CaMV35S promoter fusion with various parts 5'-upstream of the gDcPAL1 promoter. The region from -396 to -190 (relative to the transcription start site) fused to the CaMV35S core (-90) promoter showed a 280 nm-dominant response. However, gDcPAL1 promoters truncated above -570 and -396, although they contain the region between -396 and -190, did not show such a typical UVB response, i.e. they responded to 260 nm light as much as to 280 nm light. The promoter truncated to below -190 also responded to 260 nm light as much as to 280 nm light. Therefore we assumed that the gDcPAL1 promoter is composed of three functionally different parts: the upstream above -570 (modulator), the region from -396 to -190 (UVB responsive) and the down-stream below -190 (UVB and C responsive). The overall UVB response of the gDcPAL1 full-length promoter is explained as the result of interaction of these three components.