The influences of phytohormones on triacylglycerol accumulation in an oleaginous marine diatom Phaeodactylum tricornutum

Environmental stresses such as nitrate deprivation and high light are effective at increasing lipid content in microalgae, but they can also slow down and even stop growth. In this study, the phytohormones methyl jasmonate, salicylic acid, gibberellin, abscisic acid, and ethephon were introduced to cultures of the oleaginous marine diatom Phaeodactylum tricornutum in an attempt to increase growth and lipid production. Single-factor experiments showed that the influences of some of the phytohormones were closely related to their concentrations. Methyl jasmonate, abscisic acid, and salicylic acid promoted P. tricornutum growth and lipid accumulation at certain concentrations. The differing effects of the three phytohormones on P. tricornutum may be related to the respective phytohormone's responsive cis-regulatory elements in the upstream regions of the triacylglycerol (TAG) synthesis genes. Methyl jasmonate, abscisic acid, and salicylic acid were further studied in response surface experiments, through which a 141% increase in TAG production was attained for 10-L cultures of P. tricornutum grown under optimal conditions. This study suggests that some phytohormones can promote P. tricornutum lipid accumulation without hindering growth. It also provides another strategy for improving the production of microalgae for use as biodiesel

Topological analysis of metabolic and regulatory networks by decomposition methods

Die lebenden Organismen sind für eine wissenschaftliche Analyse zu kompliziert, wenn man sie als Ganzes und in ihrer vollen Komplexität betrachtet. Die vorliegende Arbeit behandelt die topologischen Eigenschaften von zwei wichtigen Teilen der lebenden Organismen: die metabolischen und die regulatorischen Systeme. Topolgische Eigenschaften sind solche, die durch die Netwerkstruktur bedingt werden. Ein Signalsystem ist eine spezielle Art von regulatorischem System. Zwischen den metabolischen und Signalnetzen gibt es wichtige Unterschiede, die ihre Behandlung in unterschiedlicher Weise erfordert. In der metabolischen Pfadanalyse ist das Konzept der elementaren Flussmoden bereits als ein passendes Instrument für die Charakterisierung der einfachsten essentiellen Wege in biochemischen Systemen etabliert. Wir untersuchen die Eigenschaften und Vorteile dieses Konzepts in einigen besonderen Fällen. Zuerst untersuchen wir die vielfach vorkommenden Enzyme mit niedriger Spezifität (z.B. Nukleosiddiphosphokinase, Uridinkinase, Transketolase, Transaldolase). Sie können parallel verschiedene Substrate und Produkte umwandeln. Auch die Enzym-Mechanismen sind vielfältig, wie wir mit dem Reaktionsschema für bifunktionelle Enzyme veranschaulichen. Wir betrachten dabei nur den Fall, dass ein bestimmtes aktives Zentrum mehrere Reaktionen katalysiert. Der Fall, dass das studierte Enzym mehrere solche aktiven Zentren hat, kann in den Fall mehrerer Enzyme transformiert werden, die nur ein aktives Zentrum haben. Wenn eine Krankheit das Ausgangsenzym ändert, werden dann in der Analyse auch alle ersetzenden Enzyme geändert. Es gibt zwei unterschiedliche Betrachtungsweisen, um multifunktionelle Enzyme zu beschreiben. Zum einen kann man die Gesamtreaktionen betrachten und zum anderen die elementaren Reaktionsschritte (Hemireaktionen, Halbreaktionen). Für Enzyme mit zwei oder mehr Funktionen ist es wichtig, nur linear unabhängige Funktionen zu betrachten, weil sonst zyklische elementare Moden auftreten würden, die keine Nettoumwandlung durchführen. Jedoch ist die Wahl der linear unabhängigen Funktionen nicht a priori eindeutig. Wir stellen eine Methode für das Treffen dieser Wahl vor, indem wir die konvexe Basis des Hemireaktions-Systems betrachten. Eine formale Anwendung des Algorithmus für das Berechnen der elementaren Flussmoden (Routen) erbringt das Resultat, dass die Zahl solcher Moden manchmal vom Niveau der Beschreibung abhängt, wenn einige Reaktionen reversibel sind und die Produkte der multifunktionellen Enzyme externe Metabolite sind, oder einige multifunktionelle Enzyme zum Teil die gleichen Stoffwechselprodukte umwandeln. Jedoch kann dieses Problem durch eine geeignete Deutung der Definition der elementaren Moden und die korrekte Wahl der unabhängigen Funktionen der Multifunktionsenzyme gelöst werden. Die Analyse wird durch einige kleinere Beispiele und ein größeres biochemisches Beispiel veranschaulicht, das aus dem Nukleotidmetabolismus stammt und die zwei Arten der Beschreibung für Nukleosiddiphosphokinase und Adenylatekinase vergleicht. Der Nukleotidmetabolismus spielt eine wichtige Rolle in lebenden Organismen und ist gegenüber allen möglichen Störungen in seiner internen Balance sehr empfindlich. Gefährliche Krankheiten können auftreten, wenn einige Enzyme nicht richtig funktionieren. Mit Hilfe des Konzeptes des elementaren Flussmodus erklären wir das Auftreten und den Schweregrad von Krankheiten, die auf Enzymdefizienzen basieren. Wenn ein Enzym vollständig gehemmt wird, werden einige metabolische Wege blockiert. Wenn jedoch einige alternative Wege noch bestehen, ist die Krankheit weniger gefährlich. Unsere Analyse ist darauf gerichtet, alternative Wege, wesentliche Enzyme und solche Enzyme, die immer zusammenarbeiten zu finden. Der letzte Begriff ist auch als "Enzyme subset" bekannt und stellt einen intermediären Schritt im Algorithmus zur Berechnung der elementaren Flussmoden dar. Wir diskutieren bereits bekannte und bisher nur hypothetische Mechanismen einiger Krankheiten (proliferative Krankheiten, Immundefizienzen), die auf Störungen des Nukleotidmetabolismus oder seiner Ausbeutung durch Viren und Parasiten beruhen. Die meisten Strategien, die für das Bekämpfen solcher Krankheiten eingesetzt werden, basieren auf der Unterbrechung des Nukleotidmetabolismus an bestimmten Stellen. Diese Strategien können aber auch zur Akkumulation toxischer Stoffe führen und dadurch Nebenwirkungen hervorrufen. Deswegen hilft ein besseres Verständnis dieses Systems, wirkungsvollere Medikamente zu entwickeln, und eine gute strukturelle Analyse kann viele experimentelle Bemühungen ersparen. Konzepte aus der Theorie der Petri-Netze liefern zusätzliche Werkzeuge für das Modellieren metabolischer Netzwerke. In Kapitel 4 werden die ähnlichkeiten zwischen einigen Konzepten in der traditionellen biochemischen Modellierung und analogen Konzepten aus der Petri-Netztheorie besprochen. Zum Beispiel entspricht die stochiometrische Matrix eines metabolischen Netzwerkes der Inzidenzmatrix des Petri-Netzes. Die Flussmoden und die Erhaltungs-Relationen haben die T-Invarianten beziehungsweise P-Invarianten als Gegenstücke. Wir decken die biologische Bedeutung einiger weiterer Begriffe aus der Theorie der Petri-Netze auf, nämlich "traps", "{siphons", "deadlocks" und "Lebendigkeit". Wir konzentrieren uns auf der topologischen Analyse anstatt auf die Analyse des dynamischen Verhaltens. Die geeignete Behandlung der externen Stoffwechselprodukte wird ebenfalls besprochen. Zur Illustration werden einige einfache theoretische Beispiele vorgestellt. Außerdem werden einige Petri-Netze präsentiert, die konkreten biochemischen Netzen entsprechen, um unsere Resultate zu belegen. Zum Beispiel wird die Rolle der Triosephosphatisomerase (TPI) im Metabolismus von Trypanosoma brucei ausgewertet, indem "traps" und "siphons" ermittelt werden. Alle behandelten Eigenschaften von Petri-Netzen werden anhand eines Systems illustriert, das aus dem Nukleotidmetabolismus stammt. Während viele Bemühungen für das Zerlegen metabolischer Systeme, (elementare Flußmoden, extreme Wege) erfolgt sind, sind bisher unseres Wissens keine Versuche in dieser Richtung für Signalübertragungssysteme unternommen worden. Eine spezielle Eigenschaft von Signalnetzwerken in lebenden Zellen ist, dass Aktivierungen, Hemmungen und biochemische Reaktionen normalerweise gleichzeitig anwesend sind. Selbst wenn sie nicht Reaktionen enthalten, machen Mehrfach-Aktivierungen oder Mehrfach-Hemmungen die Netzwerke in hohem Grade verzweigt. Es ist eine schwierige und sehr zeitraubende Aufgabe, alle Faktoren, die einen Einfluss auf ein gegebenes Ziel haben, ohne eine automatische Methode zu ermitteln. Bereits in Kapitel 1 heben wir die ähnlichkeiten und Unterschiede zwischen den metabolischen und Signal-Netzwerken hervor. In Kapitel 5 errichten wir einen Rahmen und präsentieren einen Algorithmus für die Zerlegung von Signalnetzwerken in kleinere Einheiten, die einfacher zu studieren und zu verstehen sind. Zwei Fälle werden untersucht: ein einfacheres, wenn nur monomolekulare Aktivierungen oder Reaktionen anwesend sind, und ein komplizierterer Fall, wenn die Aktivierungen und die Reaktionen multimolekular sein können. Ihre Beschreibung erfordert unterschiedliche Methoden: klassische Graphen bzw. Petrinetze. Wir besprechen die Probleme, die in unserem Modell wegen des Vorhandenseins von Hemmungen oder von unbekannten Effekten im Netz auftreten. Der vorgeschlagene Algorithmus ermittelt die Faktoren, die zusammenwirken und die Zielsubstanzen, die auf dem gleichen Weg beeinflusst werden. Die Zyklen, die im System auftreten, und mögliche fehlende Reaktionen werden ebenfalls ermittelt . Theoretische Beispiele veranschaulichen unsere Resultate. Anhand der T-Zell-Antigen-Rezeptor-Signalkaskade zeigen wir, wie die Methoden in realen Systemen angewendet werden können.The living organisms are too complex when considering them as a whole. The present thesis deals with the topological properties of two important parts of living organisms: the metabolic and the regulatory systems. The topological properties are those features that are determined by the network structure. A classification in metabolic and regulatory systems is often used. A signalling system is a special kind of regulatory system. Between metabolic and signalling networks, there are important differences that impose their treatment in different ways. In metabolic pathway analysis, the elementary flux mode concept is already established as a proper tool for identifying the smallest essential routes in biochemical systems. We examine its features and advantages in some particular cases. Firstly, many enzymes operate with low specificity (e.g. nucleoside diphosphokinase, uridine kinase, transketolase, transaldolase), so that various substrates and products can be converted. Also the enzymatic mechanisms are diverse, as we have illustrated with reaction schemes for bifunctional enzymes. Therefore, there are two different approaches to describe multifunctional enzymes (We considered only the case when a certain active site hosts several reactions. The case when the studied enzyme has several such active sites can be transformed into that of several enzymes having only one active site. If a disease alters the initial enzyme, also all substituting enzymes are altered.): in terms of overall reactions and in terms of reactions steps (hemi-reactions, half-reactions). For enzymes with two or more functions, it is important to consider only linearly independent functions, because otherwise cyclic elementary modes would occur which do not perform any net transformation. However, the choice of linearly independent functions is not a priori unique. In Chapter 2, we give a method for making this choice unique by considering the convex basis of the hemi-reactions system. The set of linearly independent functions provided by our algorithm coincides, in the case of transketolase in pentose phosphate pathway, with the set of linearly independent functions mentioned in literature. A formal application of the algorithm for computing elementary flux modes (pathways) yields the result that the number of such modes sometimes depends on the level of description if some reactions are reversible and the products of the multifunctional enzymes are external metabolites or some multifunctional enzymes partly share the same metabolites. However, this problem can be solved by appropriate interpretation of the definition of elementary modes and the correct choice of independent functions of multifunctional enzymes. The analysis is illustrated by a biochemical example taken from nucleotide metabolism, comparing the two ways of description for nucleoside diphosphokinase and adenylate kinase, and by several smaller examples. The nucleotide metabolism plays an important role in living organisms and is very sensitive to any perturbations in its internal balance. Dangerous diseases may occur if some enzymes do not work properly. With the help of elementary flux mode concept, we explain the occurrence and severity of diseases based on enzyme deficiencies. If an enzyme is completely inhibited, some metabolic routes are blocked. If, however, some alternative routes still exist, the disease is less dangerous. In Chapter 3, we focus on finding alternative routes, essential enzymes and enzymes operating together. The latter notion is also known as ,,enzyme subset`` and represents an intermediary step in calculating the elementary flux modes. The known or hypothesised mechanisms of several disorders, occurred due to the malfunctioning of nucleotide metabolism (proliferative diseases, immunodeficiency diseases) or due to its hijacking by viruses and parasites, are given. Most strategies adopted for curing such diseases are based on nucleotide metabolism interruption. Therefore, a better understanding of this system helps developing more effective drugs and a good structural analysis can spare many experimental efforts. Petri net concepts provide additional tools for the modelling of metabolic networks. In Chapter 4, the similarities between the counterparts in traditional biochemical modelling and Petri net theory are discussed. For example, the stoichiometry matrix of a metabolic network corresponds to the incidence matrix of the Petri net. The flux modes and conservation relations have the T-invariants, respectively, P-invariants as counterparts. We reveal the biological meaning of some notions specific to the Petri net framework (traps, siphons, deadlocks, liveness). We focus on the topological analysis rather than on the analysis of the dynamic behaviour. The treatment of external metabolites is discussed. Some simple theoretical examples are presented for illustration. Also the Petri nets corresponding to some biochemical networks are built to support our results. For example, the role of triose phosphate isomerase (TPI) in Trypanosoma brucei metabolism is evaluated by detecting siphons and traps. All Petri net properties treated in above-mentioned chapter (4) are exemplified on a system extracted from nucleotide metabolism. While for decomposing metabolic systems, many efforts have been done (elementary flux modes, convex basis, extreme pathways), for signalling maps, as far as we know, no attempt in this direction has been made. A special characteristic of signalling networks is that activations, inhibitions, and biochemical reactions are normally present in parallel. Even if they do not contain reactions, multi-part activations or inhibitions make them highly branched. To detect all factors that have an influence on a given target, without using an automatic method, is a difficult and very time-consuming effort. Already in Chapter 1 (Backgrounds), we highlight the similarities and differences between metabolic and signalling networks. In Chapter 5, we build a framework and algorithm for decomposing signalling networks in smaller units, which are easier to study and understand. Two cases are investigated: a simpler one, when only monomolecular activations or reactions are present, and a more complex case, when the activations and reactions can be multimolecular. Their description requires different instruments: classical graphs and Petri nets, respectively. We discuss the problems that occur in our model due to the presence of some inhibitions or unknown effects in the network. The algorithm that we propose detects the factors that are acting together and the targets that are affected on the same route. The cycles that occur in the system are also highlighted. We point out possible missing reactions. Theoretical examples illustrate out findings. Using the T cell antigen-receptor signalling cascade, we show how it can be applied to real systems

Exogenous calcium delays grape berry maturation in the white cv. loureiro while increasing fruit firmness and flavonol content

Vineyard calcium (Ca) sprays have been increasingly used by grape growers to improve fruit firmness and thus maintain quality, particularly in periods of heavy rains and hail. The observation that Ca visibly modified berry size, texture, and color in the most prominent white cultivar of the DOC region Vinhos Verdes, cultivar (cv.) Loureiro, led us to hypothesize that Ca induced metabolic rearrangements that resulted in a substantial delay in fruit maturation. Targeted metabolomics by ultra-performance liquid chromatography coupled to mass spectrometry and directed transcriptomics were thus combined to characterize the metabolic and transcriptional profiles of cv. Loureiro berries that, together with firmness, °Brix, and fruit weight measurements, allowed to obtain an integrated picture of the biochemical and structural effects of Ca in this cultivar. Results showed that exogenous Ca decreased amino acid levels in ripe berries while upregulating PAL1 expression, and stimulated the accumulation of caftaric, coutaric, and fertaric acids. An increase in the levels of specific stilbenoids, namely E-piceid and E--viniferin, was observed, which correlated with the upregulation of STS expression. Trace amounts of anthocyanins were detected in berries of this white cultivar, but Ca treatment further inhibited their accumulation. The increased berry flavonol content upon Ca treatment confirmed that Ca delays the maturation process, which was further supported by an increase in fruit firmness and decrease in weight and °Brix at harvest. This newly reported effect may be specific to white cultivars, a topic that deserves further investigation.This work was supported by the “Contrato-Programa” UIDB/04050/2020 funded by Portuguese national funds through the FCT IP. This work was also supported by FCT, CCDR-N (Norte Portugal Regional Coordination and Development Commission), European Funds (FEDER/POCI/COMPETE2020) through the project AgriFood XXI (NORTE-01-0145- FEDER-000041) and the research projects BerryPlastid (PTDC/BIA-FBT/28165/2017 and POCI-01-0145-FEDER 028165), and MitiVineDrought (PTDC/BIA-FBT/30341/2017 and POCI-01-0145-FEDER-030341). AT was supported by a postdoctoral researcher contract/position within the project “BerryPlastid”. The Région-Centre Val de Loire (France) supported this work under the grant agreement to Projects CEPATLAS and VINODRONE to AL. This work also benefited from the networking activities within the European COST Action CA 17111 INTEGRAPE, the CoLAB VINES & WINES, and the CoLAB 4FOOD – Collaborative Laboratory for Innovation in the Food Industryinfo:eu-repo/semantics/publishedVersio

Homo- and Hetero-Dimers of CAD Enzymes Regulate Lignification and Abiotic Stress Response in Moso Bamboo

Lignin biosynthesis enzymes form complexes for metabolic channelling during lignification and these enzymes also play an essential role in biotic and abiotic stress response. Cinnamyl alcohol dehydrogenase (CAD) is a vital enzyme that catalyses the reduction of aldehydes to alcohols, which is the final step in the lignin biosynthesis pathway. In the present study, we identified 49 CAD enzymes in five Bambusoideae species and analysed their phylogenetic relationships and conserved domains. Expression analysis of Moso bamboo PheCAD genes in several developmental tissues and stages revealed that among the PheCAD genes, PheCAD2 has the highest expression level and is expressed in many tissues and PheCAD1, PheCAD6, PheCAD8 and PheCAD12 were also expressed in most of the tissues studied. Co-expression analysis identified that the PheCAD2 positively correlates with most lignin biosynthesis enzymes, indicating that PheCAD2 might be the key enzyme involved in lignin biosynthesis. Further, more than 35% of the co-expressed genes with PheCADs were involved in biotic or abiotic stress responses. Abiotic stress transcriptomic data (SA, ABA, drought, and salt) analysis identified that PheCAD2, PheCAD3 and PheCAD5 genes were highly upregulated, confirming their involvement in abiotic stress response. Through yeast two-hybrid analysis, we found that PheCAD1, PheCAD2 and PheCAD8 form homo-dimers. Interestingly, BiFC and pull-down experiments identified that these enzymes form both homo- and hetero- dimers. These data suggest that PheCAD genes are involved in abiotic stress response and PheCAD2 might be a key lignin biosynthesis pathway enzyme. Moreover, this is the first report to show that three PheCAD enzymes form complexes and that the formation of PheCAD homo- and hetero- dimers might be tissue specific

Tissue-selective estrogen complexes with bazedoxifene prevent metabolic dysfunction in female mice

Pairing the selective estrogen receptor modulator bazedoxifene (BZA) with estrogen as a tissue-selective estrogen complex (TSEC) is a novel menopausal therapy. We investigated estrogen, BZA and TSEC effects in preventing diabetisity in ovariectomized mice during high-fat feeding. Estrogen, BZA or TSEC prevented fat accumulation in adipose tissue, liver and skeletal muscle, and improved insulin resistance and glucose intolerance without stimulating uterine growth. Estrogen, BZA and TSEC improved energy homeostasis by increasing lipid oxidation and energy expenditure, and promoted insulin action by enhancing insulin-stimulated glucose disposal and suppressing hepatic glucose production. While estrogen improved metabolic homeostasis, at least partially, by increasing hepatic production of FGF21, BZA increased hepatic expression of Sirtuin1, PPARα and AMPK activity. The metabolic benefits of BZA were lost in estrogen receptor-α deficient mice. Thus, BZA alone or in TSEC produces metabolic signals of fasting and caloric restriction and improves energy and glucose homeostasis in female mice

Additional Clues for a Protective Role ofVitamin D in Neurodegenerative Diseases: 1,25-Dihydroxyvitamin D3 Triggers an Anti-Inflammatory Response in BrainPericytes

International audienceEpidemiological and experimental studies suggest that 1,25-dihydroxyvitamin D3 (1,25D) plays a neuroprotectiverole in neurodegenerative diseases including Alzheimer's disease. Most of the experimental data regarding the genes regulatedby this hormone in brain cells have been obtained with neuron and glial cells. Pericytes play a critical role in brain function thatencompasses their classical function in blood-brain barrier control and maintenance. However, the gene response of brain pericyteto 1,25D remains to be investigated. Analyses of the transcriptomic response of human brain pericytes to 1,25D demonstrate thathuman brain pericytes in culture respond to 1,25D by regulating genes involved in the control of neuroinflammation. In addition,ericytes respond to the pro-inflammatory cytokines tumor necrosis factor and Interferon by inducing the expression of theCYP27B1 gene which is involved in 1,25D synthesis. Taken together, these results suggest that neuroinflammation could triggerthe synthesis of 1,25D by brain pericytes, which in turn respond to the hormone by a global anti-inflammatory response. Thesefindings identify brain pericytes as a novel 1,25D-responsive cell type and provide additional evidence for the potential value ofvitamin D in the prevention or therapy of Alzheimer's disease and other neurodegenerative/neuropsychiatric diseases associatedwith an inflammatory component

Homo- and Hetero-Dimers of CAD Enzymes Regulate Lignification and Abiotic Stress Response in Moso Bamboo

Lignin biosynthesis enzymes form complexes for metabolic channelling during lignification and these enzymes also play an essential role in biotic and abiotic stress response. Cinnamyl alcohol dehydrogenase (CAD) is a vital enzyme that catalyses the reduction of aldehydes to alcohols, which is the final step in the lignin biosynthesis pathway. In the present study, we identified 49 CAD enzymes in five Bambusoideae species and analysed their phylogenetic relationships and conserved domains. Expression analysis of Moso bamboo PheCAD genes in several developmental tissues and stages revealed that among the PheCAD genes, PheCAD2 has the highest expression level and is expressed in many tissues and PheCAD1, PheCAD6, PheCAD8 and PheCAD12 were also expressed in most of the tissues studied. Co-expression analysis identified that the PheCAD2 positively correlates with most lignin biosynthesis enzymes, indicating that PheCAD2 might be the key enzyme involved in lignin biosynthesis. Further, more than 35% of the co-expressed genes with PheCADs were involved in biotic or abiotic stress responses. Abiotic stress transcriptomic data (SA, ABA, drought, and salt) analysis identified that PheCAD2, PheCAD3 and PheCAD5 genes were highly upregulated, confirming their involvement in abiotic stress response. Through yeast two-hybrid analysis, we found that PheCAD1, PheCAD2 and PheCAD8 form homo-dimers. Interestingly, BiFC and pull-down experiments identified that these enzymes form both homo- and hetero- dimers. These data suggest that PheCAD genes are involved in abiotic stress response and PheCAD2 might be a key lignin biosynthesis pathway enzyme. Moreover, this is the first report to show that three PheCAD enzymes form complexes and that the formation of PheCAD homo- and hetero- dimers might be tissue specific

Arginase 1 expression is increased during hepatic stellate cell activation and facilitates collagen synthesis

Activation of hepatic stellate cells (HSC) is a key event in the initiation of liver fibrosis. Activated HSCs proliferate and secrete excessive amounts of extracellular matrix (ECM), disturbing liver architecture and function, leading to fibrosis and eventually cirrhosis. Collagen is the most abundant constituent of ECM and proline is the most abundant amino acid of collagen. Arginine is the precursor in the biosynthetic pathway of proline. Arginine is the exclusive substrate of both nitric oxide synthase (NOS) and arginase. NOS is an M1 (proinflammatory) marker of macrophage polarization whereas arginase-1 (Arg1) is an M2 (profibrogenic) marker of macrophage polarization. Differential expression of NOS and Arg1 has not been studied in HSCs yet. To identify the expression profile of arginine catabolic enzymes during HSC activation and to investigate their role in HSC activation, primary rat HSCs were cultured-activated for 7 days and expression of iNOS and Arg1 were investigated. Nor-NOHA was used as a specific and reversible arginase inhibitor. During HSC activation, iNOS expression decreased whereas Arg1 expression increased. Inhibition of Arg1 in activated HSCs efficiently inhibited collagen production but not cell proliferation. HSC activation is accompanied by a switch of arginine catabolism from iNOS to Arg1. Inhibition of Arg1 decreases collagen synthesis. Therefore, we conclude that Arg1 can be a therapeutic target for the inhibition of liver fibrogenesis.</p

Polyketide reductases in defense-related parasorboside biosynthesis in Gerbera hybrida share processing strategies with microbial polyketide synthase systems

Plant polyketides are well-known for their crucial functions in plants and their importance in the context of human health. They are synthesized by type III polyketide synthases (PKSs) and their final functional diversity is determined by post-PKS tailoring enzymes. Gerbera hybrida is rich in two defense-related polyketides: gerberin and parasorboside. Their synthesis is known to be initiated by GERBERA 2-PYRONE SYNTHASE 1 (G2PS1), but the polyketide reductases (PKRs) that determine their final structure have not yet been identified. We identified two PKR candidates in the pathway, GERBERA REDUCTASE 1 (GRED1) and GRED2. Gene expression and metabolite analysis of different gerbera tissues, cultivars, and transgenic gerbera plants, and in vitro enzyme assays, were performed for functional characterization of the enzymes. GRED1 and GRED2 catalyze the second reduction step in parasorboside biosynthesis. They reduce the proximal keto domain of the linear CoA bound intermediate before lactonization. We identified a crucial tailoring step in an important gerbera PKS pathway and show that plant polyketide biosynthesis shares processing strategies with fungi and bacteria. The two tailoring enzymes are recruited from the ancient sporopollenin biosynthetic pathway to a defense-related PKS pathway in gerbera. Our data provide an example of how plants recruit conserved genes to new functions in secondary metabolism that are important for environmental adaptation.Peer reviewe

Understanding the Mechanism of Action of Melatonin, Which Induces ROS Production in Cancer Cells

Reactive oxygen species (ROS) constitute a group of highly reactive molecules that have evolved as regulators of important signaling pathways. In this context, tumor cells have an altered redox balance compared to normal cells, which can be targeted as an antitumoral therapy by ROS levels and by decreasing the capacity of the antioxidant system, leading to programmed cell death. Melatonin is of particular importance in the development of innovative cancer treatments due to its oncostatic impact and lack of adverse effects. Despite being widely recognized as a pro-oxidant molecule in tumor cells, the mechanism of action of melatonin remains unclear, which has hindered its use in clinical treatments. The current review aims to describe and clarify the proposed mechanism of action of melatonin inducing ROS production in cancer cells in order to propose future anti-neoplastic clinical applications.MCIN/AEI, SpainEuropean Commission SAF2017-85903-P ID2020-115112RB-I00Consejeria de Innovacion, Ciencia y Empresa Junta de Andalucia P07-CTS-03135 P10-CTS-5784 CTS-101University of Granada, Spain UCE-PP2017-05Spanish Governmen