Expression of 3β‐HSD and P5βR, Genes Respectively Coding for Δ5-3β-Hydroxysteroid Dehydrogenase and Progesterone 5β‐Reductase, in Leaves and Cell Cultures of Digitalis lanata EHRH

Plants of the genus Digitalis produce 5β-cardenolides that are used in the therapy of cardiac insufficiency in humans. 3β-Hydroxysteroid dehydrogenase (3β-HSD) and progesterone 5β-reductase (P5βR) are both supposed to be important enzymes in the biosynthesis of these natural products. Activity and gene expression were demonstrated for both enzymes in cardenolide-accumulating leaves of Digitalis lanata but also in cardenolide-free permanent cell suspension cultures initiated from D. lanata leaf tissue. Enzyme activities were determined and quantified by HPLC and GC-MS methods. Expression of the respective genes, namely AY585867.1 (P5βR gene) and DQ466890.1 (3β-HSD gene), was made evident by real-time polymerase chain reaction (qPCR) analysis. We demonstrate for the first time that the P5βR gene, encoding an enzyme described as a key enzyme in cardenolide biosynthesis, is also expressed in cardenolide-free tissues of cardenolide-containing plants.