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Metabolic engineering of cannabinoid biosynthesis in tobacco

Geißler, Marcus Frank (2021)
Metabolic engineering of cannabinoid biosynthesis in tobacco.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00019075
Dissertation, Erstveröffentlichung, Verlagsversion

Kurzbeschreibung (Abstract)

For millennia, Cannabis has been used in various cultural groups because of its versatile applications. Among other things, the plant served as a source of textile fibers, but was also used as a medicine to treat inflammation, cramps or epilepsy. With the discovery of the endocannabinoid system, the plant, which had fallen into disrepute in the mid-20th century because of its excessive use as a recreational drug and is therefore still subject to heavy restrictions in most countries, gained new prestige. Thus, it was found that certain secondary metabolites, known as cannabinoids, could modulate a variety of physiological processes, potentially offering new therapeutic applications. To date, more than 100 of these cannabinoids have been isolated, the best known of which are the psychoactive-acting Δ9 tetrahydrocannabinol (THC) and the non-psychotropic cannabidiol (CBD). In this context, THC- and CBD-containing products such as Sativex® and Epidyolex®, which are already approved as pharmaceuticals, are finding application in medicine. However, THC is considered a major limitation for clinical use due to its psychoactive character, so non-psychotropic cannabinoids, as well as synthetic non-naturally-occurring cannabinoids that have similar medicinal properties to THC, but do not have the undesirable side effect, will be of key importance in the future. Given that chemical production of synthetic cannabinoids is very costly, heterologous production in host organisms could provide a remedy, potentially leading to industrial-scale production of rare phytocannabinoids or novel synthetic cannabinoid pharmaceuticals not readily offered by cannabis plants. In this regard, the aim was to establish tobacco as an alternative host organism for the biosynthetic production of cannabinoids. It was shown that it was possible to produce all enzymes involved in cannabinoid biosynthesis in transiently transformed Nicotiana benthamiana plants and to detect their activity in vitro. Moreover, transient expression of aae1, ols, and oac and supplementation of hexanoic acid in vivo resulted in the formation of both, the cannabinoid precursor olivetolic acid (OA) and the new-to-nature C-4 OA glucoside. However, beyond the synthesis of OA, it was not yet possible to reconstruct the biosynthetic pathway in vivo, probably due to the lack of sufficient geranyl diphosphate (GPP) supply within tobacco plants. To enable efficient production of cannabinoids in the future, it is therefore essential to eliminate this bottleneck in the biosynthetic pathway. In addition to the transient approach, stably transformed liquid cell cultures were generated, which expressed the necessary genes for the production of OA or its glucoside. This should, with a view to use in industrial production, enable large-scale cultivation in bioreactors under GMP conditions. In this context, it was possible to integrate the individual genes into Nicotiana tabacum by stable transformation. However, in contrast to transient expression, neither the synthesis of OA nor its glucoside could be detected, most likely due to a mutation in the OLS gene that was used. The second part of the work dealt with the characterization of the cannabinoid-forming synthases Δ9 tetrahydrocannabinolic acid synthase (THCAS), cannabichromenic acid synthase (CBCAS) and cannabidiolic acid synthase (CBDAS). It was found that N-glycosylation and therefore localization of the proteins via the secretory pathway, either into the apoplast or vacuole, is required for the production of the enzymes in planta. In addition, in vitro experiments with THCAS and CBDAS showed that when organic solvents such as acetonitrile or acetone were added, the product specificity of the enzymes changed from Δ9 tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA), respectively, to the synthesis of cannabichromenic acid (CBCA). This in turn indicates that, among other things, also the hydrophobic environment in the glandular trichomes of Cannabis could be responsible for the cannabinoid diversity in different Cannabis strains. Since CBCAS has a 93 % amino acid identity to THCAS but does not produce THCA, it stands to reason that small differences in amino acid sequence outside the catalytic center affect cyclization specificities. Therefore, final mutagenesis studies were performed with CBCAS and the goal of producing THCA to gain further insight into the catalytic mechanisms of the synthases. However, none of the so far introduced mutations resulted in the production of the desired cannabinoid, thus further site-directed mutagenesis have to be performed in the future, including the initially neglected amino acids.

Typ des Eintrags: Dissertation
Erschienen: 2021
Autor(en): Geißler, Marcus Frank
Art des Eintrags: Erstveröffentlichung
Titel: Metabolic engineering of cannabinoid biosynthesis in tobacco
Sprache: Englisch
Referenten: Warzecha, Prof. Dr. Heribert ; Bertl, Prof. Dr Adam
Publikationsjahr: 2021
Ort: Darmstadt
Kollation: XIV, 123 Seiten
Datum der mündlichen Prüfung: 11 Juni 2021
DOI: 10.26083/tuprints-00019075
URL / URN: https://tuprints.ulb.tu-darmstadt.de/19075
Kurzbeschreibung (Abstract):

For millennia, Cannabis has been used in various cultural groups because of its versatile applications. Among other things, the plant served as a source of textile fibers, but was also used as a medicine to treat inflammation, cramps or epilepsy. With the discovery of the endocannabinoid system, the plant, which had fallen into disrepute in the mid-20th century because of its excessive use as a recreational drug and is therefore still subject to heavy restrictions in most countries, gained new prestige. Thus, it was found that certain secondary metabolites, known as cannabinoids, could modulate a variety of physiological processes, potentially offering new therapeutic applications. To date, more than 100 of these cannabinoids have been isolated, the best known of which are the psychoactive-acting Δ9 tetrahydrocannabinol (THC) and the non-psychotropic cannabidiol (CBD). In this context, THC- and CBD-containing products such as Sativex® and Epidyolex®, which are already approved as pharmaceuticals, are finding application in medicine. However, THC is considered a major limitation for clinical use due to its psychoactive character, so non-psychotropic cannabinoids, as well as synthetic non-naturally-occurring cannabinoids that have similar medicinal properties to THC, but do not have the undesirable side effect, will be of key importance in the future. Given that chemical production of synthetic cannabinoids is very costly, heterologous production in host organisms could provide a remedy, potentially leading to industrial-scale production of rare phytocannabinoids or novel synthetic cannabinoid pharmaceuticals not readily offered by cannabis plants. In this regard, the aim was to establish tobacco as an alternative host organism for the biosynthetic production of cannabinoids. It was shown that it was possible to produce all enzymes involved in cannabinoid biosynthesis in transiently transformed Nicotiana benthamiana plants and to detect their activity in vitro. Moreover, transient expression of aae1, ols, and oac and supplementation of hexanoic acid in vivo resulted in the formation of both, the cannabinoid precursor olivetolic acid (OA) and the new-to-nature C-4 OA glucoside. However, beyond the synthesis of OA, it was not yet possible to reconstruct the biosynthetic pathway in vivo, probably due to the lack of sufficient geranyl diphosphate (GPP) supply within tobacco plants. To enable efficient production of cannabinoids in the future, it is therefore essential to eliminate this bottleneck in the biosynthetic pathway. In addition to the transient approach, stably transformed liquid cell cultures were generated, which expressed the necessary genes for the production of OA or its glucoside. This should, with a view to use in industrial production, enable large-scale cultivation in bioreactors under GMP conditions. In this context, it was possible to integrate the individual genes into Nicotiana tabacum by stable transformation. However, in contrast to transient expression, neither the synthesis of OA nor its glucoside could be detected, most likely due to a mutation in the OLS gene that was used. The second part of the work dealt with the characterization of the cannabinoid-forming synthases Δ9 tetrahydrocannabinolic acid synthase (THCAS), cannabichromenic acid synthase (CBCAS) and cannabidiolic acid synthase (CBDAS). It was found that N-glycosylation and therefore localization of the proteins via the secretory pathway, either into the apoplast or vacuole, is required for the production of the enzymes in planta. In addition, in vitro experiments with THCAS and CBDAS showed that when organic solvents such as acetonitrile or acetone were added, the product specificity of the enzymes changed from Δ9 tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA), respectively, to the synthesis of cannabichromenic acid (CBCA). This in turn indicates that, among other things, also the hydrophobic environment in the glandular trichomes of Cannabis could be responsible for the cannabinoid diversity in different Cannabis strains. Since CBCAS has a 93 % amino acid identity to THCAS but does not produce THCA, it stands to reason that small differences in amino acid sequence outside the catalytic center affect cyclization specificities. Therefore, final mutagenesis studies were performed with CBCAS and the goal of producing THCA to gain further insight into the catalytic mechanisms of the synthases. However, none of the so far introduced mutations resulted in the production of the desired cannabinoid, thus further site-directed mutagenesis have to be performed in the future, including the initially neglected amino acids.

Alternatives oder übersetztes Abstract:
Alternatives AbstractSprache

Seit Jahrtausenden wird Cannabis in diversen Kulturen aufgrund ihrer vielseitigen Anwendungsmöglichkeiten genutzt. So diente die Pflanze unter anderem als Quelle für Textilfasern, fand aber auch als Arzneimittel zur Behandlung von Entzündungen, Krämpfen oder Epilepsie Verwendung. Mit der Entdeckung des Endocannabinoid-Systems erlangte die Pflanze, die Mitte des 20. Jahrhunderts wegen ihres übermäßigen Gebrauchs als Freizeitdroge in Verruf geraten war und bis heute in den meisten Ländern starken Restriktionen unterliegt, neues Ansehen. So fand man heraus, dass bestimmte Sekundärmetabolite, sogenannte Cannabinoide, eine Vielzahl von physiologischen Prozessen modulieren konnten und somit potentiell neue therapeutische Anwendungsmöglichkeiten eröffneten. Bis heute wurden mehr als 100 dieser Cannabinoide isoliert, von welchen die bekanntesten das psychoaktiv-wirkende Δ9 Tetrahydrocannabinol (THC) und das nicht-psychotrope Cannabidiol (CBD) darstellen. In diesem Zusammenhang finden die bereits als Arzneimittel zugelassenen THC- und CBD-haltigen Produkte wie Sativex® und Epidyolex® Anwendung in der Medizin. Allerdings gilt THC aufgrund seines psychoaktiven Charakters als große Einschränkung für den klinischen Einsatz, weshalb nicht-psychotrope Cannabinoide sowie synthetische, nicht natürlich-vorkommende Cannabinoide, die ähnliche medizinische Eigenschaften wie THC aufweisen, aber nicht die unerwünschte Nebenwirkung haben, in Zukunft von zentraler Bedeutung sein werden. Da die chemische Produktion synthetischer Cannabinoide jedoch sehr kostspielig ist, könnte die heterologe Produktion in Wirtsorganismen Abhilfe schaffen und möglicherweise zu einer Produktion seltener Phytocannabinoide oder neuartiger synthetischer Cannabinoid-Pharmazeutika im industriellen Maßstab führen, die durch den reinen Gebrauch von Cannabispflanzen nicht ohne weiteres zu Verfügung stehen. Im Hinblick darauf sollte Tabak als potentielle Produktionsplattform für die biosynthetische Herstellung von Cannabinoiden etabliert werden. Dabei konnte gezeigt werden, dass es möglich war alle an der Cannabinoid-Biosynthese beteiligten Enzyme in transient transformierten Tabakpflanzen zu produzieren und deren Aktivität in vitro nachzuweisen. Darüber hinaus führte die transiente Expression von aae1, ols und oac und die Supplementierung von Hexansäure in vivo sowohl zur Bildung des Cannabinoid-Vorläufermoleküls Olivetolsäure (OA) als auch zur Bildung des neuartigen C 4 OA-Glukosids. Über die Synthese von OA hinaus war es jedoch nicht möglich, den Biosyntheseweg in vivo zu rekonstruieren, was wahrscheinlich auf das Fehlen einer ausreichenden Versorgung mit Geranyldiphosphat (GPP) innerhalb der Pflanze zurückzuführen ist. Um zukünftig eine effiziente Produktion von Cannabinoiden zu ermöglichen, ist es daher essentiell diesen Engpass im Biosyntheseweg zu beseitigen. Zusätzlich zum transienten Ansatz sollten zudem stabil transformierte Flüssigzellkulturen generiert werden, welche die notwendigen Gene für die Produktion von OA oder dessen Glukosid exprimierten. Dies sollte im Hinblick auf einen Einsatz in der industriellen Produktion, eine großtechnische Kultivierung in Bioreaktoren unter GMP-Bedingungen ermöglichen. Im Gegensatz zur transienten Expression konnte jedoch weder die Synthese von OA noch dessen Glukosid nachgewiesen werden, was höchstwahrscheinlich einer Mutation im genutzten OLS-Gen zuzuschreiben ist. Der zweite Teil der Arbeit beschäftigte sich mit der Charakterisierung der Cannabionid-bildenden Synthasen Δ9 Tetrahydrocannabinolsäure-Synthase (THCAS), Cannabichromensäure-Synthase (CBCAS) und Cannabidiolsäure-Synthase (CBDAS). Dabei stellte sich heraus, dass für die Produktion der Enzyme in planta eine N-Glykosylierung und damit verbunden eine Lokalisation der Proteine über den sekretorischen Weg, entweder in den Apoplasten oder die Vakuole, vonnöten ist. Zudem zeigte sich in in vitro Versuchen mit THCAS und CBDAS, dass sich unter Zugabe von organischen Lösemitteln wie Acetonitril oder Aceton, die Produktspezifität der Enzyme von Δ9 Tetrahydrocannabinolsäure (THCA) beziehungsweise Cannabidiolsäure (CBDA) hin zur Synthese von Cannabichromensäure (CBCA) änderte. Dies wiederrum könnte darauf hindeuten, dass unter anderem die hydrophobe Umgebung in den Drüsentrichomen von Cannabis für die Cannabinoid-Diversität in verschiedenen Cannabis Varietäten verantwortlich ist. Da die CBCAS eine Aminosäure-Identität von 93 % gegenüber der THCAS aufweist, jedoch kein THCA produziert, liegt es nahe, dass kleine Unterschiede in der Aminosäuresequenz außerhalb des katalytischen Zentrums die Zyklisierungsspezifitäten beeinflussen. Daher wurden abschließend Mutagenese-Studien mit CBCAS und dem Ziel THCA zu produzieren, durchgeführt, um weitere Einblicke in die katalytischen Mechanismen der Synthasen erhalten. Allerdings führte keine der eingeführten Mutationen zur Produktion des gewünschten Cannabinoids, weshalb in Zukunft weitere ortsgerichtete Mutagenesen durchgeführt werden müssen, die auch die zunächst vernachlässigten Aminosäuren mit einschließen.

Deutsch
Status: Verlagsversion
URN: urn:nbn:de:tuda-tuprints-190750
Sachgruppe der Dewey Dezimalklassifikatin (DDC): 500 Naturwissenschaften und Mathematik > 570 Biowissenschaften, Biologie
Fachbereich(e)/-gebiet(e): 10 Fachbereich Biologie
10 Fachbereich Biologie > Plant Biotechnology and Metabolic Engineering
Hinterlegungsdatum: 09 Jul 2021 06:47
Letzte Änderung: 13 Jul 2021 05:06
PPN:
Referenten: Warzecha, Prof. Dr. Heribert ; Bertl, Prof. Dr Adam
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: 11 Juni 2021
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