Genetic engineering approach using early Vinca alkaloid biosynthesis genes led to increased tryptamine and terpenoid indole alkaloids biosynthesis in differentiating cultures of Catharanthus roseus

Inhibition of Food-Borne Pathogen Growth and Biogenic Amine Synthesis by Spice Extracts

Food-borne pathogens and their toxins cause significant health problems in humans. Formation of biogenic amines (BAs) produced by microbial decarboxylation of amino acids in food is undesirable because it can induce toxic effects in consumers. Therefore, it is crucial to investigate the effects of natural additives with high bioactivity like spice extracts to inhibit the growth of these bacteria and the formation of BAs in food. In the present study, the antibacterial effects of diethyl ether spice (sumac, cumin, black pepper, and red pepper) extracts at doses of 1% (w/v) on Gram-positive (Staphylococcus aureus and Enterococcus faecalis) and Gram-negative (Klebsiella pneumoniae, Pseudomonas aeruginosa, Campylobacter jejuni, Aeromonas hydrophila, Salmonella Paratyphi A, and Yersinia enterocolitica) food-borne pathogen bacterial strains (FBP) were established. In addition, the accumulation of ammonia (AMN), trimethylamine (TMA), and biogenic amines (BAs) in tyrosine decarboxylase broth (TDB) was investigated by using high performance liquid chromatography (HPLC). Sumac extract exhibited the highest antibacterial potential against all FBPs, followed by cumin and peppers. AMN (570.71 mg/L) and TMA (53.66 mg/L) production were strongly inhibited by sumac extract in the levels of 55.10 mg/L for Y. enterocolitica and 2.76 mg/L for A. hydrophila, respectively. With the exception of S. aureus, black pepper dramatically reduced the synthesis of putrescine, serotonin, dopamine, and agmatine by FBP especially for Gram-negative ones. Furthermore, sumac extracts inhibited histamine and tyramine production by the majority of FBP. This research suggests the application of sumac extracts as natural preservatives for inhibiting the growth of FBPs and limiting the production of AMN, TMA, and BAs.

Vinca alkaloids as a potential cancer therapeutics: recent update and future challenges

Vinca alkaloids including vincristine, vinblastine, vindesine, and vinflunine are chemotherapeutic compounds commonly used to treat various cancers. Vinca alkaloids are one of the first microtubule-targeting agents to be produced and certified for the treatment of hematological and lymphatic neoplasms. Microtubule targeting agents like vincristine and vinblastine work by disrupting microtubule dynamics, causing mitotic arrest and cell death. The key issues facing vinca alkaloids applications include establishing an environment-friendly production technique based on microorganisms, as well as increasing bioavailability without causing harm to patient's health. The low yield of these vinca alkaloids from the plant and the difficulty of meeting their huge colossal demand around the globe prompted researchers to create a variety of approaches. Endophytes could thus be selected to produce beneficial secondary metabolites required for the biosynthesis of vinca alkaloids. This review covers the significant aspects of these vital drugs, from their discovery to the present day, in a concise manner. In addition, we emphasize the major hurdles that must be overcome in the coming years to improve vinca alkaloid's effectiveness.

Ethyl Methane Sulfonate and Sodium Azide-Mediated Chemical and X-ray-Mediated Physical Mutagenesis Positively Regulate Peroxidase 1 Gene Activity and Biosynthesis of Antineoplastic Vinblastine in Catharanthus roseus

Catharanthus roseus synthesizes bioactive therapeutic metabolites, known as monoterpenoid indole alkaloids (MIAs), including antineoplastic vinblastine and vincristine, which have high global demand, and antihypertensive ajmalicine, a serpentine. However, the in planta biosynthesis and accumulation of these phytopharmaceuticals are very low, attributed to their high cytotoxicity in the plant. Considering the low in planta concentration and over-harvesting of plant resources, biotechnological interventions have been undertaken to enhance the production of MIAs in plant systems. The present study was carried out to mutation through chemical and physical mutagenesis with sodium azide, ethyl methane sulfonate and X-rays, respectively, on C. roseus to determine their possible effects on the transcriptional modulation of MIA biosynthetic pathways in planta. The chemical mutagenesis resulted in delayed seed pod development in mutated C. roseus plants, with distinct leaf morphology and flower color. However, X-ray mutagenesis resulted in pollen-less sterile flowers. An HPLC analysis confirmed the higher catharanthine, vindoline and vinblastine content in sodium azide and X-ray mutants, and was further supported by higher PRX1 transcript levels estimated through real-time PCR analysis. The transcription factors WRKY1 and ORCA2 were found negatively regulated along with major MIA pathway genes in chemical mutants and their M₁ generation, but showed positive regulation in X-ray M₀ mutants. The induced mutagenesis of C. roseus provides a prospective strategy to modulate plant transcriptomes and enhance the biosynthesis of pharmaceutically important antineoplastic vinblastine in the plant.

Engineering Catharanthus roseus monoterpenoid indole alkaloid pathway in yeast

Catharanthus roseus (Madagascar periwinkle), a medicinal plant possessing high pharmacological attributes, is widely recognized for the biosynthesis of anticancer monoterpenoid indole alkaloids (MIAs) - vinblastine and vincristine. The plant is known to biosynthesize more than 130 different bioactive MIAs, highly acclaimed in traditional and modern medicinal therapies. The MIA biosynthesis is strictly regulated at developmental and spatial-temporal stages and requires a well-defined cellular and sub-cellular compartmentation for completion of the entire MIAs biosynthesis. However, due to their cytotoxic nature, the production of vinblastine and vincristine occurs in low concentrations in planta and the absence of chemical synthesis alternatives projects a huge gap in demand and supply, leading to high market price. With research investigations spanning more than four decades, plant tissue culture and metabolic engineering (ME)-based studies were attempted to explore, understand, explain, improve and enhance the MIA biosynthesis using homologous and heterologous systems. Presently, metabolic engineering and synthetic biology are the two powerful tools that are contributing majorly in elucidating MIA biosynthesis. This review concentrates mainly on the efforts made through metabolic engineering of MIAs in heterologous microbial factories. KEY POINTS: • Yeast engineering provides alternative production source of phytomolecules • Yeast engineering also helps to discover missing plant pathway enzymes and genes.

A Rapid and Efficient Vacuum-Based Agroinfiltration Protocol for Transient Gene Overexpression in Leaves of Catharanthus roseus

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. roseus, tools for transient overexpression remain scarce. Here, we describe an efficient and reliable methodology for transiently overexpressing any gene of interest in C. roseus leaves. This protocol combines a vacuum-based Agroinfiltration approach and the high translational efficiency of a deconstructed virus-based binary vector (pEAQ-HT). The described methodology is robust, easy to perform, and results in high amount of transient expression in C. roseus. This protocol is expected to serve as valuable tool to enhance the in planta characterization of gene functions or even transiently knock-in novel enzymatic activities.

Biosynthesis and Modulation of Terpenoid Indole Alkaloids in Catharanthus roseus: A Review of Targeting Genes and Secondary Metabolites

The medicinal plant C. roseus synthesizes biologically active alkaloids via the terpenoid indole alkaloid (TIAs) biosynthetic pathway. Most of these alkaloids have high therapeutic value, such as vinblastine and vincristine. Plant signaling components, plant hormones, precursors, growth hormones, prenylated proteins, and transcriptomic factors regulate the complex networks of TIA biosynthesis. For many years, researchers have been evaluating the scientific value of the TIA biosynthetic pathway and its potential in commercial applications for market opportunities. Metabolic engineering has revealed the major blocks in metabolic pathways regulated at the molecular level, unknown structures, metabolites, genes, enzyme expression, and regulatory genes. Conceptually, this information is necessary to create transgenic plants and microorganisms for the commercial production of high-value dimer alkaloids, such as vinca alkaloids, vinblastine, and vincristine In this review, we present current knowledge of the regulatory mechanisms of these components in the C. roseus TIA pathway, from genes to metabolites.

Terpenoid indole alkaloid biosynthesis in Catharanthus roseus: effects and prospects of environmental factors in metabolic engineering

Plants synthesize a vast array of specialized metabolites that primarily contribute to their defense and survival under adverse conditions. Many of the specialized metabolites have therapeutic values as drugs. Biosynthesis of specialized metabolites is affected by environmental factors including light, temperature, drought, salinity, and nutrients, as well as pathogens and insects. These environmental factors trigger a myriad of changes in gene expression at the transcriptional and posttranscriptional levels. The dynamic changes in gene expression are mediated by several regulatory proteins that perceive and transduce the signals, leading to up- or down-regulation of the metabolic pathways. Exploring the environmental effects and related signal cascades is a strategy in metabolic engineering to produce valuable specialized metabolites. However, mechanistic studies on environmental factors affecting specialized metabolism are limited. The medicinal plant Catharanthus roseus (Madagascar periwinkle) is an important source of bioactive terpenoid indole alkaloids (TIAs), including the anticancer therapeutics vinblastine and vincristine. The emerging picture shows that various environmental factors significantly alter TIA accumulation by affecting the expression of regulatory and enzyme-encoding genes in the pathway. Compared to our understanding of the TIA pathway in response to the phytohormone jasmonate, the impacts of environmental factors on TIA biosynthesis are insufficiently studied and discussed. This review thus focuses on these aspects and discusses possible strategies for metabolic engineering of TIA biosynthesis. PURPOSE OF WORK: Catharanthus roseus is a rich source of bioactive terpenoid indole alkaloids (TIAs). The objective of this work is to present a comprehensive account of the influence of various biotic and abiotic factors on TIA biosynthesis and to discuss possible strategies to enhance TIA production through metabolic engineering.

The combination of R2R3-MYB gene AmRosea1 and hairy root culture is a useful tool for rapidly induction and production of anthocyanins in Antirrhinum majus L

Anthocyanins are the largest group of water-soluble pigments and beneficial for human health. Although most plants roots have the potential to express natural biosynthesis pathways required to produce specialized metabolites such as anthocyanins, the anthocyanin synthesis is specifically silenced in roots. To explore the molecular mechanism of absence and production ability of anthocyanin in the roots, investigated the effect of a bHLH gene AmDelila, and an R2R3-MYB gene AmRosea1, which are the master regulators of anthocyanin biosynthesis in Antirrhinum majus flowers, by expressing these genes in transformed hairy roots of A. majus. Co-ectopic expression of both AmDelila and AmRosea1 significantly upregulated the expression of the key target structural genes in the anthocyanin biosynthesis pathway. Furthermore, this resulted in strongly enhanced anthocyanin accumulation in transformed hairy roots. Ectopic expression of AmDelila alone did not gives rise to any significant anthocyanin accumulation, however, ectopic expression of AmRosea1 alone clearly upregulated expression of the main structural genes as well as greatly promoted anthocyanin accumulation in transformed hairy roots, where the contents reached 0.773–2.064 mg/g fresh weight. These results suggest that AmRosea1 plays a key role in the regulatory network in controlling the initiation of anthocyanin biosynthesis in roots, and the combination of AmRosea1 and hairy root culture is a powerful tool to study and production of anthocyanins in the roots of A. majus.

Production of bioactive plant secondary metabolites through in vitro technologies-status and outlook

Medicinal plants have been used by mankind since ancient times, and many bioactive plant secondary metabolites are applied nowadays both directly as drugs, and as raw materials for semi-synthetic modifications. However, the structural complexity often thwarts cost-efficient chemical synthesis, and the usually low content in the native plant necessitates the processing of large amounts of field-cultivated raw material. The biotechnological manufacturing of such compounds offers a number of advantages like predictable, stable, and year-round sustainable production, scalability, and easier extraction and purification. Plant cell and tissue culture represents one possible alternative to the extraction of phytochemicals from plant material. Although a broad commercialization of such processes has not yet occurred, ongoing research indicates that plant in vitro systems such as cell suspension cultures, organ cultures, and transgenic hairy roots hold a promising potential as sources for bioactive compounds. Progress in the areas of biosynthetic pathway elucidation and genetic manipulation has expanded the possibilities to utilize plant metabolic engineering and heterologous production in microorganisms. This review aims to summarize recent advances in the in vitro production of high-value plant secondary metabolites of medicinal importance.

Key points

• Bioactive plant secondary metabolites are important for current and future use in medicine

• In vitro production is a sustainable alternative to extraction from plants or costly chemical synthesis

• Current research addresses plant cell and tissue culture, metabolic engineering, and heterologous production

Strictosidine synthase, an indispensable enzyme involved in the biosynthesis of terpenoid indole and β-carboline alkaloids

Terpenoid indole (TIAs) and β-carboline alkaloids (BCAs), such as suppressant reserpine, vasodilatory yohimbine, and antimalarial quinine, are natural compounds derived from strictosidine. These compounds can exert powerful pharmacological effects but be obtained from limited source in nature. the whole biosynthetic pathway of TIAs and BCAs, The Pictet-Spengler reaction catalyzed by strictosidine synthase (STR; EC: 4.3.3.2) is the rate-limiting step. Therefore, it is necessary to investigate their biosynthesis pathways, especially the role of STR, and related findings will support the biosynthetic generation of natural and unnatural compounds. This review summarizes the latest studies concerning the function of STR in TIA and BCA biosynthesis, and illustrates the compounds derived from strictosidine. The substrate specificity of STR based on its structure is also summarized. Proteins that contain six-bladed four-stranded β-propeller folds in many organisms, other than plants, are listed. The presence of these folds may lead to similar functions among organisms. The expression of STR gene can greatly influence the production of many compounds. STR is mainly applied to product various valuable drugs in plant cell suspension culture and biosynthesis in other carriers.

Plant regeneration and transformation of Trachyspermum ammi using Agrobacterium tumefaciens and zygotic embryos

BACKGROUND

Trachyspermum ammi is one of the key medicinal plant species with many beneficial properties. Thymol is the most important substance in the essential oil of this plant. Thymol is a natural monoterpene phenol with high anti-microbial, anti-bacterial, and anti-oxidant properties. Thymol in the latest research has a significant impact on slowing the progression of cancer cells in human. In this research, embryos were employed as convenient explants for the fast and effectual regeneration and transformation of T. ammi. To regenerate this plant, Murashige and Skoog (MS) and Gamborg's B5 (B5) media were supplemented with diverse concentrations of plant growth regulators, such as 6-benzyladenine (BA), 1-naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), and kinetin (kin). Transgenic Trachyspermum ammi plants were also obtained using Agrobacterium-mediated transformation and zygotic embryos explants. Moreover, two Agrobacterium tumefaciens strains (EHA101 and LBA4404) harboring pBI121-TPS2 were utilized for genetic transformation to Trachyspermum ammi.

RESULTS

According to the obtained results, the highest plant-regeneration frequency was obtained with B5 medium supplemented with 0.5 mg/l BA and 1 mg/l NAA. The integrated gene was also approved using the PCR reaction and the Southern blot method. Results also showed that the EHA101 strain outperformed another strain in inoculation time (30 s) and co-cultivation period (1 day) (transformation efficiency 19.29%). Furthermore, HPLC method demonstrated that the transformed plants contained a higher thymol level than non-transformed plants.

CONCLUSIONS

In this research, a fast protocol was introduced for the regeneration and transformation of Trachyspermum ammi, using zygotic embryo explants in 25-35 days. Our findings confirmed the increase in the thymol in the aerial part of Trachyspermum ammi. We further presented an efficacious technique for enhancing thymol content in Trachyspermum ammi using Agrobacterium-mediated plant transformation system that can be beneficial in genetic transformation and other plant biotechnology techniques.

Confirmation of "pre-plasmolysis mediated ex-osmosis hypothesis" to obtain shoot bud morphogenesis in Catharanthus roseus

The antineoplastic herb, Catharanthus roseus is a classified high-value low-volume medicinal herb which is in global attention of scientific research for modulation of its monoterpenoid indole alkaloids (MIA) pathway through genetic engineering. These secondary metabolites are generally stored in specific types of structures/compartments due to their cytotoxic nature and designated roles in plant defense response. However, their presence can hinder the genetic engineering process used to develop transgenic plants through de novo morphogenesis and regeneration of plants from cultured cells/tissues and hence, it always remained a critical impediment in transgenic research in C. roseus. The pre-plasmolysis treatment of leaf explants can help to tackle the recalcitrant nature of leaf explant and can support the direct regeneration response by ex-osmosis that minimizes the concentration of alkaloids. Therefore, this study was performed to chase the effect of osmotic conditions on recalcitrant leaves of C. roseus engaged in vitro plant regeneration and hypothesis of alkaloids ex-osmosis is confirmed by HPLC analysis.

Silent constraints: the hidden challenges faced in plant metabolic engineering

Metabolic engineering is embraced as a method to sustainably enhance production of valuable phytochemicals with beneficial properties. However, successful production of these compounds in plants is not always predictable even when the pathways are fully known, frequently due to the lack of comprehensive understanding of plant metabolism as a whole, and interconnections between different primary, secondary, and hormone metabolic networks. Here, we highlight critical hidden constraints, including substrate availability, silent metabolism, and metabolic crosstalk, that impair engineering strategies. We explore how these constraints have historically been manifested in engineering attempts and propose how modern advancements will enable future strategies to overcome these impediments.

From Ethnomedicine to Plant Biotechnology and Machine Learning: The Valorization of the Medicinal Plant Bryophyllum sp

The subgenus Bryophyllum includes about 25 plant species native to Madagascar, and is widely used in traditional medicine worldwide. Different formulations from Bryophyllum have been employed for the treatment of several ailments, including infections, gynecological disorders, and chronic diseases, such as diabetes, neurological and neoplastic diseases. Two major families of secondary metabolites have been reported as responsible for these bioactivities: phenolic compounds and bufadienolides. These compounds are found in limited amounts in plants because they are biosynthesized in response to different biotic and abiotic stresses. Therefore, novel approaches should be undertaken with the aim of achieving the phytochemical valorization of Bryophyllum sp., allowing a sustainable production that prevents from a massive exploitation of wild plant resources. This review focuses on the study of phytoconstituents reported on Bryophyllum sp.; the application of plant tissue culture methodology as a reliable tool for the valorization of bioactive compounds; and the application of machine learning technology to model and optimize the full phytochemical potential of Bryophyllum sp. As a result, Bryophyllum species can be considered as a promising source of plant bioactive compounds, with enormous antioxidant and anticancer potential, which could be used for their large-scale biotechnological exploitation in cosmetic, food, and pharmaceutical industries.

Indole alkaloids: 2012 until now, highlighting the new chemical structures and biological activities

Indole alkaloids have attracted attention because of their therapeutic properties, being anti-inflammatory, antinociceptive, antitumoural, antioxidant and antimicrobial. These compounds present a wide structural diversity, which is directly related to the genera of the producing plants, as well as the biological activities. Indole alkaloids have attracted attention over the last decade because of this combination of bioactivity and structural diversity. Therefore, this review presented recent (2012-2018) advances in alkaloids, focusing on new compounds, extraction methods and biological activities. As such, approximately 70 articles were identified, which showed 261 new compounds produced by plants of the families Apocynaceae, Rubiaceae, Annonaceae and Loganiaceae. In addition, different extraction methods were identified, and the structures of the new compounds were analysed. In addition to indole molecules, there were mono-indole-, di-indole-, vinblastine-, vimblastine-, gelsedine-, geissospermidine-, koumine-, geissospermidine-, iboga-, perakine-, corynanthe-, vincamine-, ajmaline-, aspidorpema-, strychnos-type, β-carboline alkaloids and indole alkaloid glucosides. The reported biological activities are mainly anticancer, antibacterial, antimalarial, antifungal, antiparasitic, and antiviral, as well as anti-acetylcholinesterase and anti-butyrylcolinesterase properties. This review serves as a guide for those wishing to find the most recently identified alkaloid structures and their associated activities.

Application of genetics and biotechnology for improving medicinal plants

Plant tissue culture has been used for conservation, micropropagation, and in planta overproduction of some pharma molecules of medicinal plants. New biotechnology-based breeding methods such as targeted genome editing methods are able to create custom-designed medicinal plants with different secondary metabolite profiles. For a long time, humans have used medicinal plants for therapeutic purposes and in food and other industries. Classical biotechnology techniques have been exploited in breeding medicinal plants. Now, it is time to apply faster biotechnology-based breeding methods (BBBMs) to these valuable plants. Assessment of the genetic diversity, conservation, proliferation, and overproduction are the main ways by which genetics and biotechnology can help to improve medicinal plants faster. Plant tissue culture (PTC) plays an important role as a platform to apply other BBBMs in medicinal plants. Agrobacterium-mediated gene transformation and artificial polyploidy induction are the main BBBMs that are directly dependent on PTC. Manageable regulation of endogens and/or transferred genes via engineered zinc-finger proteins or transcription activator-like effectors can help targeted manipulation of secondary metabolite pathways in medicinal plants. The next-generation sequencing techniques have great potential to study the genetic diversity of medicinal plants through restriction-site-associated DNA sequencing (RAD-seq) technique and also to identify the genes and enzymes that are involved in the biosynthetic pathway of secondary metabolites through precise transcriptome profiling (RNA-seq). The sequence-specific nucleases of transcription activator-like effector nucleases (TALENs), zinc-finger nucleases, and clustered regularly interspaced short palindromic repeats-associated (Cas) are the genome editing methods that can produce user-designed medicinal plants. These current targeted genome editing methods are able to manage plant synthetic biology and open new gates to medicinal plants to be introduced into appropriate industries.

Overexpression of tryptophan decarboxylase and strictosidine synthase enhanced terpenoid indole alkaloid pathway activity and antineoplastic vinblastine biosynthesis in Catharanthus roseus

Terpenoid indole alkaloid (TIA) biosynthetic pathway of Catharanthus roseus possesses the major attention in current metabolic engineering efforts being the sole source of highly expensive antineoplastic molecules vinblastine and vincristine. The entire TIA pathway is fairly known at biochemical and genetic levels except the pathway steps leading to biosynthesis of catharanthine and tabersonine. To increase the in-planta yield of these antineoplastic metabolites for the pharmaceutical and drug industry, extensive plant tissue culture-based studies were performed to provide alternative production systems. However, the strict spatiotemporal developmental regulation of TIA biosynthesis has restricted the utility of these cultures for large-scale production. Therefore, the present study was performed to enhance the metabolic flux of TIA pathway towards the biosynthesis of vinblastine by overexpressing two upstream TIA pathway genes, tryptophan decarboxylase (CrTDC) and strictosidine synthase (CrSTR), at whole plant levels in C. roseus. Whole plant transgenic of C. roseus was developed using Agrobacterium tumefaciens LBA1119 strain having CrTDC and CrSTR gene cassette. Developed transgenic lines demonstrated up to twofold enhanced total alkaloid production with maximum ninefold increase in vindoline and catharanthine, and fivefold increased vinblastine production. These lines recorded a maximum of 38-fold and 65-fold enhanced transcript levels of CrTDC and CrSTR genes, respectively.

Comparison of Strategies to Overcome Drug Resistance: Learning from Various Kingdoms

Drug resistance, especially antibiotic resistance, is a growing threat to human health. To overcome this problem, it is significant to know precisely the mechanisms of drug resistance and/or self-resistance in various kingdoms, from bacteria through plants to animals, once more. This review compares the molecular mechanisms of the resistance against phycotoxins, toxins from marine and terrestrial animals, plants and fungi, and antibiotics. The results reveal that each kingdom possesses the characteristic features. The main mechanisms in each kingdom are transporters/efflux pumps in phycotoxins, mutation and modification of targets and sequestration in marine and terrestrial animal toxins, ABC transporters and sequestration in plant toxins, transporters in fungal toxins, and various or mixed mechanisms in antibiotics. Antibiotic producers in particular make tremendous efforts for avoiding suicide, and are more flexible and adaptable to the changes of environments. With these features in mind, potential alternative strategies to overcome these resistance problems are discussed. This paper will provide clues for solving the issues of drug resistance.