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[*]

Abstract

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.

Key words

Digitalis lanata - Plantaginaceae - cardiac glycosides - progesterone 5β‐reductase - Δ ⁵‐3β‐hydroxysteroiddehydrogenase - gene expression

1 Dedicated to Prof. Dr. Wolfgang Barz on the occasion of his 75^th birthday.

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1 Dedicated to Prof. Dr. Wolfgang Barz on the occasion of his 75^th birthday.