Explore the vast range of titles available.

Catharanthus roseus produces bioactive terpenoid indole alkaloids (TIAs), including the chemotherapeutics, vincristine and vinblastine. Transcriptional regulation of TIA biosynthesis is not fully understood. The jasmonic acid (JA)-responsive AP2/ERF transcription factor (TF), ORCA3, and its regulator, CrMYC2, play key roles in TIA biosynthesis. ORCA3 forms a physical cluster with two uncharacterized AP2/ERFs, ORCA4 and 5. Here, we report that (1) the ORCA gene cluster is differentially regulated; (2) ORCA4, while overlapping functionally with ORCA3, modulates an additional set of TIA genes. Unlike ORCA3, ORCA4 overexpression resulted in dramatic increase of TIA accumulation in C. roseus hairy roots. In addition, CrMYC2 is capable of activating ORCA3 and co-regulating TIA pathway genes concomitantly with ORCA3. The ORCA gene cluster and CrMYC2 act downstream of a MAP kinase cascade that includes a previously uncharacterized MAP kinase kinase, CrMAPKK1. Overexpression of CrMAPKK1 in C. roseus hairy roots upregulated TIA pathways genes and increased TIA accumulation. This work provides detailed characterization of a TF gene cluster and advances our understanding of the transcriptional and post-translational regulatory mechanisms that govern TIA biosynthesis in C. roseus.

Vinblastine and vincristine are important, expensive anticancer agents that are produced by dimerization of the plant-derived alkaloids catharanthine and vindoline. The enzymes that transform tabersonine into vindoline are known; however, the mechanism by which the scaffolds of catharanthine and tabersonine are generated has been a mystery. Caputi et al. now describe the biosynthetic genes and corresponding enzymes responsible. This resolves a long-standing question of how plant alkaloid scaffolds are synthesized, which is important not only for vinblastine and vincristine biosynthesis, but also for understanding the many other biologically active alkaloids found throughout nature. Science , this issue p. 1235 Identification of enzymes reveals pathway complexity in synthesis of bioactive alkaloids from plants. Vinblastine, a potent anticancer drug, is produced by Catharanthus roseus (Madagascar periwinkle) in small quantities, and heterologous reconstitution of vinblastine biosynthesis could provide an additional source of this drug. However, the chemistry underlying vinblastine synthesis makes identification of the biosynthetic genes challenging. Here we identify the two missing enzymes necessary for vinblastine biosynthesis in this plant: an oxidase and a reductase that isomerize stemmadenine acetate into dihydroprecondylocarpine acetate, which is then deacetoxylated and cyclized to either catharanthine or tabersonine via two hydrolases characterized herein. The pathways show how plants create chemical diversity and also enable development of heterologous platforms for generation of stemmadenine-derived bioactive compounds.

Advances in omics technologies now permit the generation of highly contiguous genome assemblies, detection of transcripts and metabolites at the level of single cells and high-resolution determination of gene regulatory features. Here, using a complementary, multi-omics approach, we interrogated the monoterpene indole alkaloid (MIA) biosynthetic pathway in Catharanthus roseus , a source of leading anticancer drugs. We identified clusters of genes involved in MIA biosynthesis on the eight C. roseus chromosomes and extensive gene duplication of MIA pathway genes. Clustering was not limited to the linear genome, and through chromatin interaction data, MIA pathway genes were present within the same topologically associated domain, permitting the identification of a secologanin transporter. Single-cell RNA-sequencing revealed sequential cell-type-specific partitioning of the leaf MIA biosynthetic pathway that, when coupled with a single-cell metabolomics approach, permitted the identification of a reductase that yields the bis-indole alkaloid anhydrovinblastine. We also revealed cell-type-specific expression in the root MIA pathway. The medicinal plant Catharanthus roseus is a source of leading anticancer drugs. The monoterpene indole alkaloid (MIA) biosynthetic pathway in C. roseus has now been analyzed using a complementary, multi-omics, single-cell approach. This identified clusters of genes involved in MIA biosynthesis and cell-type-specific partitioning in the MIA biosynthetic pathway.

Catharanthus roseus produces a large array of terpenoid indole alkaloids (TIAs) that are an important source of natural or semisynthetic anticancer drugs. The biosynthesis of TIAs is tissue specific and induced by certain phytohormones and fungal elicitors, indicating the involvement of a complex transcriptional control network. However, the transcriptional regulation of the TIA pathway is poorly understood. Here, we describe a C. roseus WRKY transcription factor, CrWRKY1, that is preferentially expressed in roots and induced by the phytohormones jasmonate, gibberellic acid, and ethylene. The overexpression of CrWRKY1 in C. roseus hairy roots up-regulated several key TIA pathway genes, especially Tryptophan Decarboxylase (TDC), well as the transcriptional repressors ZCT1 (for zinc-finger C. roseus transcription factor 1), ZCT1, and ZCT3. However, CrWRKY1 overexpression repressed the transcriptional activators ORCA2, ORCA3, and CrMYC1. Overexpression of a dominant-repressive form of CrWRKY1, created by fusing the SRDX repressor domain to CrWRKY1, resulted in the downregulation of TDC and ZCTs but the up-regulation of ORCA3 and CrMYC2. CrWRKY1 bound to the W box elements of the TDC promoter in electrophoretic mobility shift, yeast one-hybrid, and C. roseus protoplast assays. Up-regulation of TDC increased TDC activity, tryptamine concentration, and resistance to 4-methyl tryptophan inhibition of CrWRKY1 hairy roots. Compared with control roots, CrWRKY1 hairy roots accumulated up to 3-fold higher levels of serpentine. The preferential expression of CrWRKY1 in roots and its interaction with transcription factors including ORCA3, CrMYC2, and ZCTs may play a key role in determining the root-specific accumulation of serpentine in C. roseus plants.

Plants make specialized bioactive metabolites to defend themselves against attackers. The conserved control mechanisms are based on transcriptional activation of the respective plant species-specific biosynthetic pathways by the phytohormone jasmonate. Knowledge of the transcription factors involved, particularly in terpenoid biosynthesis, remains fragmentary. By transcriptome analysis and functional screens in the medicinal plant Catharanthus roseus (Madagascar periwinkle), the unique source of the monoterpenoid indole alkaloid (MIA)-type anticancer drugs vincristine and vinblastine, we identified a jasmonate-regulated basic helix–loop–helix (bHLH) transcription factor from clade IVa inducing the monoterpenoid branch of the MIA pathway. The bHLH iridoid synthesis 1 (BIS1) transcription factor transactivated the expression of all of the genes encoding the enzymes that catalyze the sequential conversion of the ubiquitous terpenoid precursor geranyl diphosphate to the iridoid loganic acid. BIS1 acted in a complementary manner to the previously characterized ethylene response factor Octadecanoid derivative-Responsive Catharanthus APETALA2-domain 3 (ORCA3) that transactivates the expression of several genes encoding the enzymes catalyzing the conversion of loganic acid to the downstream MIAs. In contrast to ORCA3 , overexpression of BIS1 was sufficient to boost production of high-value iridoids and MIAs in C. roseus suspension cell cultures. Hence, BIS1 might be a metabolic engineering tool to produce sustainably high-value MIAs in C. roseus plants or cultures. Significance Terpenoids are the largest group of plant-specialized metabolites and include many valuable bioactive compounds, such as the blockbuster anticancer drugs vincristine and vinblastine, that are monoterpenoid indole alkaloids from the medicinal plant Catharanthus roseus (Madagascar periwinkle). A master regulator was discovered that activates the biosynthesis of the iridoids, the monoterpenoid precursors of vinblastine and vincristine, and the rate-limiting branch in their biosynthetic pathway. This master regulator can be used to boost production of iridoids and monoterpenoid indole alkaloids in C. roseus cell cultures and thus represents an interesting tool for the metabolic engineering of the sustainable production of these high-value compounds in cultures of the endogenous plant species.

is the exclusive source of an array of terpenoid indole alkaloids including the anticancer drugs vincristine and vinblastine, derived from the coupling of catharanthine and vindoline. Leaf-synthesized vindoline is regulated by light. A seven-step enzymatic process is involved in the sequential conversion of tabersonine to vindoline; however, the regulatory mechanism controlling the expression of genes encoding these enzymes has not been elucidated. Here, we identified CrGATA1, an Leu-Leu-Met domain GATA transcription factor that regulates light-induced vindoline biosynthesis in seedlings. Expression of and the vindoline pathway genes , , , , and was significantly induced by light. In addition, CrGATA1 activated the promoters of five light-responsive vindoline pathway genes in plant cells. Two GATC motifs in the promoter were critical for CrGATA1-mediated transactivation. Transient overexpression of in seedlings resulted in up-regulation of vindoline pathway genes and increased vindoline accumulation. Conversely, virus-induced gene silencing of in young leaves significantly repressed key vindoline pathway genes and reduced vindoline accumulation. Furthermore, we showed that a Phytochrome Interacting Factor, CrPIF1, is a repressor of and vindoline biosynthesis. Transient overexpression or virus-induced gene silencing of in seedlings altered and vindoline pathway gene expression in the dark. CrPIF1 repressed and promoter activity by binding to G/E-box/PBE elements. Our findings reveal a regulatory module involving Phytochrome Interacting Factor -GATA that governs light-mediated biosynthesis of specialized metabolites.

Antitumor substances related to vinblastine and vincristine are exclusively found in the Catharanthus roseus (Madagascar periwinkle), a member of the Apocynaceae plant family, and continue to be extensively used in cancer chemotherapy. Although in high demand, these valuable compounds only accumulate in trace amounts in C. roseus leaves. Vinblastine and vincristine are condensed from the monoterpenoid indole alkaloid (MIA) precursors catharanthine and vindoline. Although catharanthine biosynthesis remains poorly characterized, the biosynthesis of vindoline from the MIA precursor tabersonine is well understood at the molecular and biochemical levels. This study uses virus-induced gene silencing (VIGS) to identify a cytochrome P450 [ CYP71D1V2 ; tabersonine 3-oxygenase ( T3O )] and an alcohol dehydrogenase [ ADHL1 ; tabersonine 3-reductase ( T3R )] as candidate genes involved in the conversion of tabersonine or 16-methoxytabersonine to 3-hydroxy-2,3-dihydrotabersonine or 3-hydroxy-16-methoxy-2,3-dihydrotabersonine, which are intermediates in the vindorosine and vindoline pathways, respectively. Biochemical assays with recombinant enzymes confirm that product formation is only possible by the coupled action of T3O and T3R, as the reaction product of T3O is an epoxide that is not used as a substrate by T3R. The T3O and T3R transcripts were identified in a C. roseus database representing genes preferentially expressed in leaf epidermis and suggest that the subsequent reaction products are transported from the leaf epidermis to specialized leaf mesophyll idioblast and laticifer cells to complete the biosynthesis of these MIAs. With these two genes, the complete seven-gene pathway was engineered in yeast to produce vindoline from tabersonine. Significance Bioinformatics and virus-induced gene silencing (VIGS)-guided gene discovery combined with biochemical enzyme assays show that tabersonine 3-oxygenase (T3O) and tabersonine 3-reductase (T3R) are required to form 3-hydroxy-16-methoxy-2,3-dihydrotabersonine, an intermediate in the formation of anticancer drug precursor vindoline from tabersonine. In the absence of T3R, tabersonine is converted by T3O to a series of byproducts that can no longer be used by T3R, suggesting a concerted reaction mechanism. Engineering the seven-gene pathway in yeast demonstrated a prototype platform of high potential for industrial production of the anticancer drug precursor vindoline.

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. The (seco)iridoids and their monoterpenoid indole alkaloid (MIA) derivatives are plant-derived compounds with pharmaceutical applications. Here, the authors identify the last four missing steps of the (seco)iridoid pathway, which they reconstitute in an alternative plant host to produce the complex MIA, strictosidine.

The leaves of the medicinal-ornamental plant Catharanthus roseus serve as the exclusive source of the anticancer alkaloids vinblastine and vincristine. The limited synthesis of these alkaloids, alongside efforts to enhance their production, has consistently been a focal point of research. Water scarcity, recognized as one of the most significant constraints in agriculture, has prompted this study to examine the effects of the amino acid elicitor tryptophan and drought stress on the alterations in secondary metabolites of C. roseus and the genes implicated in their biosynthetic pathways. This investigation was factorial experiment conducted within a completely randomized design (CRD) with three replications. The first factor involved drought stress (40% and 100% field capacity), the second factor pertained to tryptophan concentrations (0 and 250 ppm), and the third factor encompassed duration (24, 48, 72, and 168 hours). Key genes associated with four metabolic pathways, phenolic/flavonoid, indole, terpenoid, and alkaloid pathways, were analyzed using quantitative polymerase chain reaction (qRT- PCR). Notably, the Cm gene (phenolic/flavonoid pathway) exhibited increased expression across all treatments, with the highest expression level recorded at 168 hours under the combined conditions of tryptophan and drought. Genes associated with the indole alkaloid pathway ( As and Tdc ) demonstrated similar temporal variations, with peak expression levels observed at 24 hours, particularly under drought stress. Genes within the terpenoid pathway ( Sls ) and alkaloid pathway ( Str , Dat , Prx ) displayed an initial increase in expression at 24 hours, followed by a decline at 48 and 72 hours, and a subsequent increase at 168 hours post-treatment in comparison to the control. Additionally, alkaloid accumulation (vincristine, vinblastine) significantly increased, especially under severe drought stress, correlating with the observed gene expression patterns. Non-enzymatic antioxidants, including phenols and flavonoids, also exhibited elevated levels in response to stress and tryptophan treatment. Furthermore, tryptophan application resulted in a doubling of plant biomass compared to the control. Collectively, the findings of this study suggest that the combination of drought stress and tryptophan application modulates gene expression and metabolite production in C. roseus , which may be crucial for optimizing alkaloid biosynthesis under drought stress conditions.

Iridoids form a broad and versatile class of biologically active molecules found in thousands of plant species. In addition to the many hundreds of iridoids occurring in plants, some iridoids, such as secologanin, serve as key building blocks in the biosynthesis of thousands of monoterpene indole alkaloids (MIAs) and many quinoline alkaloids. This study describes the molecular cloning and functional characterization of three iridoid glucosyltransfeases (UDP-SUGAR GLYCOSYLTRANSFERASE6 [UGT6], UGT7, and UGT8) from Madagascar periwinkle (Catharanthus roseus) with remarkably different catalytic efficiencies. Biochemical analyses reveal that UGT8 possessed a high catalytic efficiency toward its exclusive iridoid substrate, 7-deoxyloganetic acid, making it better suited for the biosynthesis of iridoids in periwinkle than the other two iridoid glucosyltransfeases. The role of UGT8 in the fourth to last step in secologanin biosynthesis was confirmed by virus-induced gene silencing in periwinkle plants, which reduced expression of this gene and resulted in a large decline in secologanin and MIA accumulation within silenced plants. Localization studies of UGT8 using a carborundum abrasion method for RNA extraction show that its expression occurs preferentially within periwinkle leaves rather than in epidermal cells, and in situ hybridization studies confirm that UGT8 is preferentially expressed in internal phloem associated parenchyma cells of periwinkle species.