Abstract
Shikonin, a red naphthoquinone pigment, is a secondary metabolite produced in a perennial herbal plant L. erythrorhizon. In the biosynthesis of shikonin, the geranylation step catalyzed by PGT (PHB: geranyltransferase) is a regulatory key step. This enzyme activity is regulated by several chemical and physical elements, in particular it is strongly down-regulated by light irradiation. We have recently shown the expression pattern of LePGT, the gene encoding PGT in L. erythrorhizon, by in situ hybridization; i.e. LePGT is specifically expressed in the epidermis of root tissues where shikonin accumulates. Northern analysis also showed that LePGT expression was strongly suppressed by light irradiation. To further clarify of the light-regulation mechanism and tissue-specificity of LePGT expression, we isolated the promoter region of the gene by TAIL-PCR, and established reporter gene constructs, using GUS and GFP genes. We will report the promoter activities in transgenic Arabidopsis and tobacco plants.
