The seco-iridoid pathway from Catharanthus roseus

Abstract

The (seco)iridoids and their derivatives, the monoterpenoid indole alkaloids (MIAs), form two large families of plant-derived bioactive compounds with a wide spectrum of high-value pharmacological and insect-repellent activities. Vinblastine and vincristine, MIAs used as anticancer drugs, are produced by Catharanthus roseus in extremely low levels, leading to high market prices and poor availability. Their biotechnological production is hampered by the fragmentary knowledge of their biosynthesis. Here we report the discovery of the last four missing steps of the (seco)iridoid biosynthesis pathway. Expression of the eight genes encoding this pathway, together with two genes boosting precursor formation and two downstream alkaloid biosynthesis genes, in an alternative plant host, allows the heterologous production of the complex MIA strictosidine. This confirms the functionality of all enzymes of the pathway and highlights their utility for synthetic biology programmes towards a sustainable biotechnological production of valuable (seco)iridoids and alkaloids with pharmaceutical and agricultural applications.

Dual Function of the Cytochrome P450 CYP76 Family from Arabidopsis thaliana in the Metabolism of Monoterpenols and Phenylurea Herbicides

“…CYP76A26 from C. roseus has also been reported to be active with monoterpenols, although its main activity was in iridoid metabolism (Miettinen et al, 2014). Monoterpenol metabolism is thus expected to be a quite common feature of the CYP76 family in dicots.…”

“…Unexpectedly, CYP76B6, thought to be a specific geraniol oxidase dedicated to the secoiridoid/TIA pathway , emerged from the screening as the most promiscuous enzyme with regard to monoterpenols, efficiently metabolizing geraniol, nerol, linalool, citronellol, and lavandulol. CYP76B6 promiscuity thus points to the critical importance of the geraniol synthase for producing the relevant substrate for iridoid and terpene indole alkaloid production (Miettinen et al, 2014) and to the capacity of CYP76B6 and resulting duplicates for evolving multiple functions in different monoterpenolsderived pathways in the plant. In contrast with CYP76Cs from A. thaliana, CYP76B6 essentially formed with all monoterpenols a single hydroxylated derivative and its further oxidation product.…”

“…The same work also revealed a geraniol 8-and 9-hydroxylase activity of CYP76C4 from Arabidopsis thaliana. More recently, another CYP76 enzyme (CYP76A226) from C. roseus was found to metabolize oxidized geraniol derivatives and to have an iridoid oxidase activity, catalyzing the triple oxygenation of cis-trans-nepetalactol into 7-deoxyloganetic acid for the biosynthesis of secoiridoids and terpene indole alkaloids (Miettinen et al, 2014;Salim et al, 2014). Not all CYP76 enzymes seem to be devoted to the metabolism of monoterpenols.…”

Unprecedented Utilization of Pelargonidin and Indole for the Biosynthesis of Plant Indole Alkaloids

“…The indole structure is also a building block of a multitude of synthetic compounds4 that are not only used as pharmaceutical products but are also broadly applied in various technical branches 5. The Catharanthus alkaloids and other natural monoterpene indole alkaloids are biosynthesized from tryptamine and secologanin, an iridoid glycoside, to form strictosidine 6, 7…”

Engineering of gentiopicroside-producing yeast strain using low-energy ion implantation mediated synthetic biology

“…In the medical plant Catharanthus roseus, the precursors of gentiopicroside and secoiridoids are biosynthesized via the iridoid pathway and have been well studied and reviewed. [11] In higher plants, the first formation step of isopentenyl diphosphate (IPP), a precursor of terpenoids, is through to be both the plastidial methyl-erythritol phosphate (MEP) pathway and the cytosolic mevalonate (MVA) pathway. [12,13] Isomerization of IPP by IPP isomerase produces geranyl diphosphate, which is converted into geraniol via the enzyme geraniol synthase.…”