Publications by authors named "Konstantinos Koudounas"

Monoterpene indole alkaloids (MIAs) are valuable metabolites produced in numerous medicinal plants from the Apocynaceae family such as Alstonia scholaris, which synthesizes strictamine, a MIA displaying neuropharmacological properties of a potential importance. To get insights into the MIA metabolism in A. scholaris, we studied here both the spatial and transcriptional regulations of MIA genes by performing a robust transcriptomics analysis of the main plant organs, leaf epidermis but also by sequencing RNA from leaves transiently overexpressing the master transcriptional regulator MYC2.

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Article Synopsis
  • Plant-specialized metabolism is a rich source of bioactive compounds, like monoterpene indole alkaloids (MIAs), known for their health benefits including anticancer and neuroactive properties.
  • The types of MIAs, particularly pachysiphine derivatives, have promising medical applications but are found in very low quantities in certain plant species, and there is a lack of genomic data needed to enhance their production.
  • This study presents the genome sequence of the toad tree (Tabernaemontana elegans) and identifies genes that can synthesize pachysiphine, leading to engineered MIAs in yeast, thus paving the way for better production of these valuable compounds for pharmaceutical use.
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Plants produce an exceptional multitude of chemicals to compensate with challenging environments. Despite the structural pluralism of specialized metabolism, often defensive compounds are stored in planta as glycosides and reactive aglycones are conditionally activated by specific β-glucosidases-a large family of enzymes with pluripotent contribution in homeostasis and a pivotal role in plant chemical defense. Typically, these detonating enzymes are characterized by exceptional substrate specificity and, in several cases, even isoenzymes exhibit differentiated molecular or biochemical characteristics.

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Monoterpene indole alkaloids (MIAs) make up a highly bioactive class of metabolites produced by a range of tropical and subtropical plants. The corynanthe-type MIAs are a stereochemically complex subclass with therapeutic potential against a large number of indications including cancer, psychotic disorders, and erectile dysfunction. Here, we report yeast-based cell factories capable of de novo production of corynanthe-type MIAs rauwolscine, yohimbine, tetrahydroalstonine, and corynanthine.

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Monoterpenoid indole alkaloids (MIAs) represent a large class of plant natural products with marketed pharmaceutical activities against a wide range of indications, including cancer, malaria and hypertension. Halogenated MIAs have shown improved pharmaceutical properties; however, synthesis of new-to-nature halogenated MIAs remains a challenge. Here we demonstrate a platform for de novo biosynthesis of two MIAs, serpentine and alstonine, in baker's yeast Saccharomyces cerevisiae and deploy it to systematically explore the biocatalytic potential of refactored MIA pathways for the production of halogenated MIAs.

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Circuitries of signaling pathways integrate distinct hormonal and environmental signals, and influence development in plants. While a crosstalk between brassinosteroid (BR) and gibberellin (GA) signaling pathways has recently been established, little is known about other components engaged in the integration of the two pathways. Here, we provide supporting evidence for the role of HSP90 (HEAT SHOCK PROTEIN 90) in regulating the interplay of the GA and BR signaling pathways to control hypocotyl elongation of etiolated seedlings in Arabidopsis.

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The medicinal plant Catharanthus roseus biosynthesizes many important drugs for human health, including the anticancer monoterpene indole alkaloids (MIAs) vinblastine and vincristine. Over the past decades, the continuous increase in pharmaceutical demand has prompted several research groups to characterize MIA biosynthetic pathways for considering future metabolic engineering processes of supply. In line with previous work suggesting that diversification can potentially occur at various steps along the vindoline branch, we were here interested in investigating the involvement of distinct isoforms of tabersonine-16-O-methyltransferase (16OMT) which plays a pivotal role in the MIA biosynthetic pathway.

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Functional genomics analyses in planta can be hampered in non-model plants that are recalcitrant to the genetic transformation such as the medicinal plant Catharanthus roseus (Apocynaceae). No stable transformation and regeneration of plantlets have been achieved with a high efficiency in this plant to date. In addition, while virus-mediated transient gene silencing has been reported a decade ago in C.

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Many plant species from the Apocynaceae, Loganiaceae and Rubiaceae families evolved a specialized metabolism leading to the synthesis of a broad palette of monoterpene indole alkaloids (MIAs). These compounds are believed to constitute a cornerstone of the plant chemical arsenal but above all several MIAs display pharmacological properties that have been exploited for decades by humans to treat various diseases. It is established that MIAs are produced in planta due to complex biosynthetic pathways engaging a multitude of specialized enzymes but also a complex tissue and subcellular organization.

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Specialized metabolites are chemically complex small molecules with a myriad of biological functions. To investigate plant-specialized metabolite biosynthesis more effectively, we developed an improved method for virus-induced gene silencing (VIGS). We designed a plasmid that incorporates fragments of both the target gene and knockdown marker gene (phytoene desaturase, PDS), which identifies tissues that have been successfully silenced in planta.

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Article Synopsis
  • Specialized metabolism in plants helps them combat various biotic challenges, and many plant compounds are important for human medicine.
  • Olive trees produce unique compounds called oleosides, which show potential for pharmaceutical use.
  • Silencing the enzyme OeGLU in olive trees disrupts the production of secoiridoids, revealing a regulatory mechanism that may help control bioactive compounds in olive oil.
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The gram-positive pathogenic bacterium subsp. () causes bacterial canker disease in tomato, affecting crop yield and fruit quality. To understand how tomato plants respond, the dynamic expression profile of host genes was analyzed upon infection.

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Article Synopsis
  • The pharmaceutical industry is experiencing increased demand for anticancer plant drugs, facing shortages in supply due to their use in chemotherapy.
  • Researchers have developed an efficient method using yeast cell factories to convert tabersonine into vindoline, a key precursor for anticancer drugs like vinblastine and vincristine.
  • The process involved optimizing yeast gene copies and culture conditions, achieving a high yield of 266 mg/l of vindoline in a bioreactor, highlighting a potential for large-scale production from readily available tabersonine.
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Deglycosylation is a key step in the activation of specialized metabolites involved in plant defense mechanisms. This reaction is notably catalyzed by β-glucosidases of the glycosyl hydrolase 1 (GH1) family such as strictosidine β-d-glucosidase (SGD) from Catharanthus roseus. SGD catalyzes the deglycosylation of strictosidine, forming a highly reactive aglycone involved in the synthesis of cytotoxic monoterpene indole alkaloids (MIAs) and in the crosslinking of aggressor proteins.

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The lesser periwinkle accumulates numerous monoterpene indole alkaloids (MIAs) including the vasodilator vincamine. While the biosynthetic pathway of MIAs has been largely elucidated in other Apocynaceae such as , the counterpart in remains mostly unknown, especially for reactions leading to MIAs specific to this plant. As a consequence, we generated a comprehensive transcriptome elaborated from eight distinct samples including roots, old and young leaves exposed to low or high light exposure conditions.

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Olive (Olea europaea) is an important crop in Europe, with high cultural, economic and nutritional significance. Olive oil flavor and quality depend on phenolic secoiridoids, but the biosynthetic pathway of these iridoids remains largely uncharacterized. We discovered two bifunctional cytochrome P450 enzymes, catalyzing the rare oxidative C-C bond cleavage of 7-epi-loganin to produce oleoside methyl ester (OeOMES) and secoxyloganin (OeSXS), both through a ketologanin intermediary.

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Research on gene functions in non-model tree species is hampered by a number of difficulties such as time-consuming genetic transformation protocols and extended period for the production of healthy transformed offspring, among others. Virus-induced gene silencing (VIGS) is an alternative approach to transiently knock out an endogenous gene of interest (GOI) by the introduction of viral sequences encompassing a fragment of the GOI and to exploit the posttranscriptional gene silencing (PTGS) mechanism of the plant, thus triggering silencing of the GOI. Here we describe the successful application of Tobacco rattle virus (TRV)-mediated VIGS through agroinoculation of olive plantlets.

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The discovery and supply of plant-derived anti-cancer compounds remain challenging given their low bioavailability and structural complexity. Reconstituting the pathways of these compounds in heterologous hosts is a promising solution; however, requires the complete elucidation of the biosynthetic genes involved and extensive metabolic engineering to optimise enzyme activity and metabolic flux. This review describes the current strategies and recent advancements in the production of these valuable therapeutic compounds, and highlights plant-derived immunomodulators as an emerging class of anti-cancer agents.

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We have previously identified proteins in poplar which belong to an osmosensing (OS) signaling pathway, called a multistep phosphorelay (MSP). The MSP comprises histidine-aspartate kinases (HK), which act as membrane receptors; histidine phosphotransfer (HPt) proteins, which act as phosphorelay proteins; and response regulators (RR), some of which act as transcription factors. In this study, we identified the HK proteins homologous to the Arabidopsis cytokinin (CK) receptors, which are first partners in the poplar cytokinin MSP, and focused on specificity of these two MSPs (CK and OS), which seem to share the same pool of HPt proteins.

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Olive is one of the most important fruit crop trees in the history of Mediterranean because of the high quality oil. Olive oil has a well-balanced fatty acid composition along with biophenols, which make it exceptional in human diet and provide an exceptional value to the olive oil. Leaf non-glandular peltate trichomes are specialized cell types representing a protective barrier against acute environmental conditions.

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Lochnericine is a major monoterpene indole alkaloid (MIA) in the roots of Madagascar periwinkle (). Lochnericine is derived from the stereoselective C6,C7-epoxidation of tabersonine and can be metabolized further to generate other complex MIAs. While the enzymes responsible for its downstream modifications have been characterized, those involved in lochnericine biosynthesis remain unknown.

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Vinblastine, a potent anticancer drug, is produced by (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.

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