Production Of Metabolites In Plants Research Articles

Nitrogen-mediated volatilisation of defensive metabolites in tomato confers resistance to herbivores.

Plants synthesise a vast array of volatile organic compounds (VOCs), which serve as chemical defence and communication agents in their interactions with insect herbivores. Although nitrogen (N) is a critical resource in the production of plant metabolites, its regulatory effects on defensive VOCs remain largely unknown. Here, we investigated the effect of N content in tomato (Solanum lycopersicum) on the tobacco cutworm (Spodoptera litura), a notorious agricultural pest, using biochemical and molecular experiments in combination with insect behavioural and performance analyses. We observed that on tomato leaves with different N contents, S. litura showed distinct feeding preference and growth and developmental performance. Particularly, metabolomics profiling revealed that limited N availability conferred resistance upon tomato plants to S. litura is likely associated with the biosynthesis and emission of the volatile metabolite α-humulene as a repellent. Moreover, exogenous application of α-humulene on tomato leaves elicited a significant repellent response against herbivores. Thus, our findings unravel the key factors involved in N-mediated plant defence against insect herbivores and pave the way for innovation of N management to improve the plant defence responses to facilitate pest control strategies within agroecosystems.

Exploring low-dose gamma radiation effects on monoterpene biosynthesis in Thymus vulgaris: insights into plant defense mechanisms.

Thymus vulgaris, commonly known as thyme, is a plant renowned for producing monoterpenes. This study aimed to understand the effects of low-dose gamma radiation, specifically in the range of 1-5Gy, on various traits of Thymus vulgaris, providing context on its importance in agricultural and medicinal applications. The research explored morpho-physiological, biochemical, and gene-expression responses in thyme plants under no gamma- and gamma-ray exposure conditions. The study revealed complex relationships between gamma-ray doses and plant characteristics. In particular, shoot and root lengths initially increased with low doses (1-3Gy) but decreased at higher doses (5Gy), suggesting a dose-dependent threshold effect. Similarly, shoot and root fresh weights displayed an initial increase followed by a decline with increasing doses. Biochemical parameters showed dose-dependent responses, with low to moderate doses (1-3Gy) stimulating enzyme activities and high doses (5Gy) inhibiting them. Gene expression analysis was focused on the following specific genes: thymol synthase, γ-terpinene synthase, and carvacrol synthase. Low to moderate doses increased the expression of these genes, resulting in increased production of bioactive compounds. However, higher doses had diminished effects or suppressed gene expression. Metabolite analysis demonstrated dose-dependent responses, with moderate doses enhancing secondary metabolite production, while higher doses provided limited benefits. These findings underscore the implications of using gamma radiation to enhance secondary metabolite production in plants and its potential applications in agriculture, medicine, and environmental science. The study emphasizes the potential of gamma radiation as an external stressor to influence plant responses and highlights the importance of understanding such effects in various fields.

Simultaneous Impact of Rhizobacteria Inoculation and Leaf-Chewing Insect Herbivory on Essential Oil Production and VOC Emissions in Ocimum basilicum.

Inoculation with rhizobacteria and feeding by herbivores, two types of abiotic stress, have been shown to increase the production of secondary metabolites in plants as part of the defense response. This study explored the simultaneous effects of inoculation with Bacillus amyloliquefaciens GB03 (a PGPR species) and herbivory by third-instar Spodoptera frugiperda larvae on essential oil (EO) yield and volatile organic compound (VOC) emissions in Ocimum basilicum plants. The density of glandular trichomes was also examined, given that they are linked to EO production and VOC emission. Herbivory increased EO content, but inoculation on its own did not. When combined, however, the two treatments led to a 10-fold rise in EO content with respect to non-inoculated plants. VOC emissions did not significantly differ between inoculated and non-inoculated plants, but they doubled in plants chewed by the larvae with respect to their undamaged counterparts. Interestingly, no changes were observed in VOC emissions when the treatments were tested together. In short, the two biotic stressors elicited differing plant defense responses, mainly when EO was concerned. PGPR did not stimulate EO production, while herbivory significantly enhanced it and increased VOC emissions. The combined treatment acted synergistically, and in this case, PGPR inoculation may have had a priming effect that amplified plant response to herbivory. Peltate trichome density was higher in inoculated plants, those damaged by larvae, and those subjected to the combination of both treatments. The findings highlight the intricate nature of plant defense mechanisms against various stressors and hint at a potential strategy to produce essential oil through the combined application of the two stressors tested here.

Evaluation of phytochemical responses and paclitaxel content of yew (Taxus baccata) seedlings subjected to the systemic fungicides

AbstractEndophytic fungi pass all or at least a part of their life cycle inside or between host cells in living plant tissues. These fungi are not capable of causing disease in the host plants, however, they are deemed to be associated with the production of some secondary metabolites in plants. Therefore, this study was laid out to shed light on how fungicides are involved in the formation of key metabolites of yew (Taxus baccata L.), especially taxol. Through the symbiotic fungal endophyte activities and population changes an experiment was conducted as a completely randomized block design using two foliar application treatments of Rovral‐TS and Fosetyl aluminium fungicides. Plants sprayed with distilled water were used as a control. The findings revealed that the diversity of endophytic fungi declined with the application of systemic fungicides, leading to a decrease in the production of certain secondary metabolites. Specifically, the levels of paclitaxel decreased by 35%, while the photosynthetic pigments chlorophyll‐a, chlorophyll‐b and total chlorophyll decreased by 26%, 20.6% and 19.6%, respectively. Additionally, the levels of carotenoids, total phenol and total flavonoids decreased by 18%, 15% and 21.8%, respectively. The highest amount of these compounds was observed in the control treatment. An increase in antioxidant activity, soluble sugars and proline content was observed soon after fungicides application. The variation in the content of soluble sugars, proline and antioxidant activity was fungicide‐dependent. Compared to Fosetyl aluminium fungicide, the numerical value of the above parameters in plants treated with Rovral‐TS was 14.4%, 11.7% and 25.4% higher, respectively. The fungicide‐mediated induction of Taxol production—key secondary metabolites in yew—was to a great extent associated with the change in endophytic fungi. This further establishes the role of fungal endophytes in the stimulation of secondary metabolite formation in yew plants.

Secondary Metabolite Production In Plants: In Response To Biotic And Abiotic Stress Factors

Secondary metabolites (SMs) play vital roles in plant defence mechanisms, adaptation to environmental conditions, and interactions with other organisms. Biotic and abiotic stress factors can significantly influence the production, accumulation, and composition of SMs in plants. Understanding the intricate relationship between stress and SM production is crucial for enhancing plant resilience, agricultural productivity, and the development of novel phytopharmaceuticals. This research provides current knowledge regarding the impact of biotic and also abiotic stress on SMs in plants. Biotic stress factors such as pathogen infection, and herbivore attacks, as well as abiotic stress factors like drought, along with temperature extremes, and also salinity, can profoundly influence the biosynthesis and accumulation of SMs in plants. We discussed the methodology based on secondary sources underlying physiological, biochemical, and molecular mechanisms involved in stress-induced SM synthesis and highlight the potential implications for plant biology, agriculture, and human health. The study also emphasizes the functions of SMs in plants including defence against herbivores, pathogens, and abiotic stresses. The mechanism by which thesecompounds act as allelochemicals and signalling molecules is also discussed.

The Stilbene Synthase Family in Arachis: A Genome-Wide Study and Functional Characterization in Response to Stress.

Peanut (Arachis hypogaea) and its wild relatives are among the few species that naturally synthesize resveratrol, a well-known stilbenoid phytoalexin that plays a crucial role in plant defense against biotic and abiotic stresses. Resveratrol has received considerable attention due to its health benefits, such as preventing and treating various human diseases and disorders. Chalcone (CHS) and Stilbene (STS) Synthases are plant-specific type III Polyketide Synthases (PKSs) that share the same substrates and are key branch enzymes in the biosynthesis of flavonoids and stilbenoids, respectively. Although resveratrol accumulation in response to external stimulus has been described in peanut, there are no comprehensive studies of the CHS and STS gene families in the genus Arachis. In the present study, we identified and characterized 6 CHS and 46 STS genes in the tetraploid peanut and an average of 4 CHS and 22 STS genes in three diploid wild species (Arachis duranensis, Arachis ipaënsis and Arachis stenosperma). The CHS and STS gene and protein structures, chromosomal distributions, phylogenetic relationships, conserved amino acid domains, and cis-acting elements in the promoter regions were described for all Arachis species studied. Based on gene expression patterns of wild A. stenosperma STS genes in response to different biotic and abiotic stresses, we selected the candidate AsSTS4 gene, which is strongly induced by ultraviolet (UV) light exposure, for further functional investigation. The AsSTS4 overexpression in peanut hairy roots significantly reduced (47%) root-knot nematode infection, confirming that stilbene synthesis activation in transgenic plants can increase resistance to pathogens. These findings contribute to understanding the role of resveratrol in stress responses in Arachis species and provide the basis for genetic engineering for improved production of valuable secondary metabolites in plants.

Improvement of Oleanolic Acid Production in Saccharomyces Cerevisiae Based on OptKnock Framework.

Biosynthesis of plant-derived natural products in the eukaryotic microbe Saccharomyces cerevisiae often faces the issue of the inefficient production due to the poor compatibility between the heterologous genes and chassis cells. In order to improve the biosynthetic efficiency of heterologous production of plant secondary metabolites in S. cerevisiae, people usually do metabolic engineering in and around the heterologous metabolic pathways based on researchers' experience and mass of trials, which usually consumes a lot of manpower and financial resources. Herein, to further improve the heterologous production of oleanolic acid (OA), a pentacyclic triterpenoid in many plants with several promising pharmacological activities, in a genetically engineered, OA-producing strain S. cerevisiae OA07 effectively, a genome-scale metabolic model of the strain was developed, with the named as Yeast-OA07, and then OptKnock, a flux balance analysis-based pathway design algorithm with bilevel objectives, was utilized to develop in silico gene-knockout strategies to guide the molecular operations in S. cerevisiae OA07. Yeast8-OA07 contained 1133 genes, 2702 metabolites, and 3997 reactions. Five in silico gene-knockout strategies, which were expected to increase OA productivities, were obtained based on the metabolic flux analysis of Yeast8-OA07 through OptKnock. Afterwards, five mutant strains, named as LK1, LK2, LK3, LK4 and LK5, were constructed according to the in silico strategies. It was found that the mutant strain LK2, in which 2-amino-4-hydroxy-6-hydroxymethyl dihydropteridine diphosphokinase-encoding gene FOL1 and formate dehydrogenase-encoding gene FDH1 were deleted, had an OA yield of 125.04 mg·L-1, which was significantlyhigher than the original strain OA07 (89.50 mg·L-1), while the mutant strain LK5, which eliminated paminobenzoic acid synthase-encoding gene ABZ1 and glycine hydroxymethyl transferase-encoding gene SHM1, had an even higher OA yield of 207.37 mg·L-1. Nevertheless, strain LK6, which was developed by integrating the in silico gene-knockout strategies of LK2 and LK5, had a significant decrease of OA production than S. cerevisiae OA07, indicating that in silico knockout strategies do not fit to in vivo iteration directly. Our study provides a novel, efficient method to improve the heterologous production of plant metabolites in microbial cell factories.

Evaluation of the artemisinin content of Artemisia annua L. grown in different Agro ecological zones of Cameroon

Artemisinin and its derivatives are potent antimalarials that have become essential components of Artemisinin Based Combination Therapies (ACTs) for malaria treatment. Production of artemisinin is less compared to its world demand and access to ACTs is still limited in worst hit countries. Secondary metabolite production in plants depends on a number of factors including agro ecology. This work sought to evaluate the growth characteristics and artemisinin content of Artemisia annua grown in four agro ecological zones of Cameroon. Experimental fields comprising of A annua were set up in the different agro-ecological zones, for growth and artemisinin assessments. Artemisinin detection and quantification was compared in leaves/flowers and stems of Artemisia annua from these agro-ecological zones, using High-Performance Liquid Chromatography. Soil provenance and other agro ecological factors significantly affected the growth parameters of A. annua as there were significant differences (p<0.05) in plant height, leaf area, number of branches, stem girth and number of leaves across the different study areas. There was significant variation (P<0.05) in the content of artemisinin from the plant in the different agro ecological zones. The mean levels of artemisinin in the samples was 0.34-0.80% in stem samples, and 0.18-0.61% for leaves/flowers. The highest artemisinin yield in leaf/flowers samples (0.61%) was recorded in samples from Bamenda, while that of stem samples (0.80%) was recorded in samples from Ngaoundere. The study confirms the effect of agro ecological factors on artemisinin content of A. annua in Cameroon and reveal that A. annua grown in most regions of the country contain commercially viable levels of artemisinin which can further be exploited for pharmaceutical purposes.

Bioactive metabolites of plants and microbes and their role in agricultural sustainability and mitigation of plant stress

Primary metabolites are ubiquitous in nature and actively involved in growth while secondary metabolites (SMs) are involved in interaction with the environment. In plants terpenes are the largest group of secondary metabolites that play an important role in defense mechanisms against the herbivores and pathogens. Plant secondary metabolites such as alkaloids, phenolics and diterpenes have a great potential against many carcinogens. Carotenoids provide photoprotection and act as a pigment to absorb light during photosynthesis. Carotenoids are also efficient in the interaction with other organisms as they are phagostimulant and allelopathic agent. Flavonoids from the higher plants play a significant role in ultra-violet (UV) filtration, nitrogen fixation, floral pigmentation, and defense mechanisms against many diseases. These secondary metabolites provide protection to plants in a different type of biotic and abiotic stresses. Microorganisms also contain a high number of bioactive metabolites but not all of them. Marine microorganisms are a rich source of secondary metabolites such as alkaloids, terpenoids, polyketides, isoprenoids and non-isoprenoid and quinones amongst others. These metabolites are anti-inflammatory, anti-bacterial and anti-tumor in action. Secondary metabolites from fungi have a great therapeutic value as they have antifungal and antibacterial activity against many pathogens. Plant growth promoting rhizobacteria (PGPR) and Plant growth regulators (PGR) are the key biological entities to enhance the production of bioactive secondary metabolites in plants and can change the plant metabolome in response to various environmental stresses. This review paper will provide a new insight about the role of secondary metabolites in plant defense and the role of microorganisms in modulating the plant metabolome under various environmental stresses and their interactions with other microorganisms and plant growth regulators.

From Nature to Lab: A Review of Secondary Metabolite Biosynthetic Pathways, Environmental Influences, and In Vitro Approaches.

Secondary metabolites are gaining an increasing importance in various industries, such as pharmaceuticals, dyes, and food, as is the need for reliable and efficient methods of procuring these compounds. To develop sustainable and cost-effective approaches, a comprehensive understanding of the biosynthetic pathways and the factors influencing secondary metabolite production is essential. These compounds are a unique type of natural product which recognizes the oxidative damage caused by stresses, thereby activating the defence mechanism in plants. Various methods have been developed to enhance the production of secondary metabolites in plants. The elicitor-induced in vitro culture technique is considered an efficient tool for studying and improving the production of secondary metabolites in plants. In the present review, we have documented various biosynthetic pathways and the role of secondary metabolites under diverse environmental stresses. Furthermore, a practical strategy for obtaining consistent and abundant secondary metabolite production via various elicitation agents used in culturing techniques is also mentioned. By elucidating the intricate interplay of regulatory factors, this review paves the way for future advancements in sustainable and efficient production methods for high-value secondary metabolites.

Designing plant flavonoids: harnessing transcriptional regulation and enzyme variation to enhance yield and diversity.

Plant synthetic biology has emerged as a powerful and promising approach to enhance the production of value-added metabolites in plants. Flavonoids, a class of plant secondary metabolites, offer numerous health benefits and have attracted attention for their potential use in plant-based products. However, achieving high yields of specific flavonoids remains challenging due to the complex and diverse metabolic pathways involved in their biosynthesis. In recent years, synthetic biology approaches leveraging transcription factors and enzyme diversity have demonstrated promise in enhancing flavonoid yields and expanding their production repertoire. This review delves into the latest research progress in flavonoid metabolic engineering, encompassing the identification and manipulation of transcription factors and enzymes involved in flavonoid biosynthesis, as well as the deployment of synthetic biology tools for designing metabolic pathways. This review underscores the importance of employing carefully-selected transcription factors to boost plant flavonoid production and harnessing enzyme promiscuity to broaden flavonoid diversity or streamline the biosynthetic steps required for effective metabolic engineering. By harnessing the power of synthetic biology and a deeper understanding of flavonoid biosynthesis, future researchers can potentially transform the landscape of plant-based product development across the food and beverage, pharmaceutical, and cosmetic industries, ultimately benefiting consumers worldwide.

An Engineered Heat-Inducible Expression System for the Production of Casbene in Nicotiana benthamiana.

Plants respond to heat stress by producing heat-shock proteins. These are regulated by heat-shock promoters containing regulatory elements, which can be harnessed to control protein expression both temporally and spatially. In this study, we designed heat-inducible promoters to produce the diterpene casbene in Nicotiana benthamiana, through a multi-step metabolic pathway. To potentially increase gene transcription, we coupled heat-shock elements from Arabidopsis thaliana Hsp101 or Glycine max GmHsp17.3-B promoters, CAAT and TATA boxes from CaMV 35S, and the 5'UTR from the tobacco mosaic virus. The resulting four chimeric promoters fused to a green fluorescent protein (GFP) reporter showed that the variant Ara2 had the strongest fluorescent signal after heat shock. We next created a 4-gene cassette driven by the Ara2 promoter to allow for exogenous synthesis of casbene and transformed this multigene construct along with a selectable marker gene into Nicotiana benthamiana. Metabolic analysis on the transgenic lines revealed that continuous heat outperforms heat shock, with up to 1 μg/mg DW of casbene detected after 32 h of uninterrupted 40 °C heat. These results demonstrate the potential of heat-inducible promoters as synthetic biology tools for metabolite production in plants.

Microbial synthetic biology for plant metabolite production: a strategy to reconcile human health with the realization of the UN Sustainable Development Goals

AbstractPlants produce a wide range of secondary metabolites that provide an array of benefits for human health. Challenges of native host production systems such as excessive land use, large carbon footprints, long production times, and high production costs often make plant‐based production of these critical metabolites inefficient and unsustainable. Engineered production through microbial‐based synthetic biology offers an alternative method of producing plant compounds that addresses the limitations encountered in plant‐based production. New technological and analytical tools such as bioprospecting, machine learning, and protein modeling can be used to explore biodiversity‐based data to identify more efficient enzymatic sequences for optimizing the production of plant derivatives. Ex planta production using microbial chassis systems provides a flexible, scalable metabolic platform that can more readily integrate new metabolic processes. Potential improvements include increased production rates and enhanced bioavailability of critical compounds, expanding the frontiers of metabolite production for optimized clinical applications. Microbial‐based synthetic biology also opens an avenue for sustainable production, with the capability of modifying the microbial chassis to accommodate a wide variety of substrates for feedstock. It includes the utilization of waste from human activities as carbon sources for production, presenting an opportunity to use cheap renewable resources for greener production methods. The benefits of ex planta production systems can potentially enable the efficient, scalable, and sustainable production of plant derivatives that may vastly improve health and help bring forward the realization of the 2030 UN Sustainable Development Goals.

Molecular and genetic insights into secondary metabolic regulation underlying insect-pest resistance in legumes.

Insect pests pose a major threat to agricultural production, resulting in significant economic losses for countries. A high infestation of insects in any given area can severely reduce crop yield and quality. This review examines the existing resources for managing insect pests and highlights alternative eco-friendly techniques to enhance insect pest resistance in legumes. Recently, the application of plant secondary metabolites has gained popularity in controlling insect attacks. Plant secondary metabolites encompass a wide range of compounds such as alkaloids, flavonoids, and terpenoids, which are often synthesized through intricate biosynthetic pathways. Classical methods of metabolic engineering involve manipulating key enzymes and regulatory genes to enhance or redirect the production of secondary metabolites in plants. Additionally, the role of genetic approaches, such as quantitative trait loci mapping, genome-wide association (GWAS) mapping, and metabolome-based GWAS in insect pest management is discussed, also, the role of precision breeding, such as genome editing technologies and RNA interference for identifying pest resistance and manipulating the genome to develop insect-resistant cultivars are explored, highlighting the positive contribution of plant secondary metabolites engineering-based resistance against insect pests. It is suggested that by understanding the genes responsible for beneficial metabolite compositions, future research might hold immense potential to shed more light on the molecular regulation of secondary metabolite biosynthesis, leading to advancements in insect-resistant traits in crop plants. In the future, the utilization of metabolic engineering and biotechnological methods may serve as an alternative means of producing biologically active, economically valuable, and medically significant compounds found in plant secondary metabolites, thereby addressing the challenge of limited availability.

Enhancing secondary metabolite production in plants: Exploring traditional and modern strategies

The biosynthesis of secondary metabolites (SMs) in plants occurs in various forms and amounts, and their use in modern medicine is widespread. Half of the human necessities are derived from plant-based commodities, including fuel, cosmetics, pharmaceuticals, building materials, and food essentials. Many medicinal plant species are utilized for their therapeutic properties and their SMs content, but the amount of naturally occurring SMs in plants are limited. Therefore, various conventional and novel strategies are employed to enhance the production of bioactive components from plants. Traditional methods are cost-effective, easy, and faster, but produce fewer metabolites, while modern techniques such as metabolic pathways engineering, genome editing, metabolic transformation, biotechnology-based substitutions, and synthetic biology are more expensive but offer valuable tools for augmenting SMs content. Optimizing culture media and signalling pathways involved in SMs production presents an exciting opportunity to increase the quantity of bioactive compounds naturally present. This review summarizes the different cultivation methods used to enhance the class and quantity of metabolites produced and highlights the benefits of strategies for boosting SMs and synthesizing metabolites using various techniques.

Mixed elicitation with salicylic acid and hydrogen peroxide modulates the phenolic and iridoid pathways in Castilleja tenuiflora plants.

SA and H2O2, in single and mixed elicitation stimulate specialized metabolism and activate oxidative stress in C. tenuiflora plants. Single elicitation with salicylic acid (SA at 75µM) and, hydrogen peroxide (at 150µM), and mixed elicitation (75µM SA + 150µM H2O2) were evaluated on specialized metabolism in Castilleja tenuiflora Benth. plants. Total phenolic content (TPC), phenylalanine ammonia-lyase (PAL) activity, antioxidant enzymes and specialized metabolite profiles, as well as the expression levels of eight genes involved in phenolic (Cte-TyrDC, Cte-GOT2, Cte-ADD, Cte-AO3, Cte-PAL1, Cte-CHS1) and terpene pathways (Cte-DXS1 and Cte-G10H) and their correlation with major metabolite (verbascoside and aucubin) concentrations were investigated. TPC content (three-fold) and PAL activity (11.5-fold) increased with mixed elicitation, as well as catalase and peroxidase activity (11.3-fold and 10.8-fold, respectively), compared to single elicitation. Phenylethanoid accumulation was greatest under mixed elicitation, followed by SA and H2O2. Lignan accumulation was differential, depending on the plant part and the elicitor. Flavonoids only appeared after mixed elicitation. The high concentration of verbascoside under mixed elicitation was related to a high gene expression. Single elicitation induced iridoid accumulation in specific parts (H2O2 in aerial parts and SA in roots), whereas under mixed elicitation, it accumulated in both parts. A high concentration of aucubin in the aerial part was related to a high expression level of genes of the terpene pathway Cte-DXS1 and Cte-G10H, and in the root with Cte-G10H, while Cte-DXS1 was downregulated in this tissue in all treatments. Mixed elicitation with SA and H2O2 represents an interesting tool to increase the production of specialized metabolites in plants.

(-)-Loliolide is a general signal of plant stress that activates jasmonate-related responses.

The production of defensive metabolites in plants can be induced by signaling chemicals released by neighboring plants. Induction is mainly known from volatile aboveground signals, with belowground signals and their underlying mechanisms largely unknown. We demonstrate that (-)-loliolide triggers defensive metabolite responses to competitors, herbivores, and pathogens in seven plant species. We further explore the transcriptional responses of defensive pathways to verify the signaling role of (-)-loliolide in wheat and rice models with well-known defensive metabolites and gene systems. In response to biotic and abiotic stressors, (-)-loliolide is produced and secreted by roots. This, in turn, induces the production of defensive compounds including phenolic acids, flavonoids, terpenoids, alkaloids, benzoxazinoids, and cyanogenic glycosides, regardless of plant species. (-)-Loliolide also triggers the expression of defense-related genes, accompanied by an increase in the concentration of jasmonic acid and hydrogen peroxide (H2 O2 ). Transcriptome profiling and inhibitor incubation indicate that (-)-loliolide-induced defense responses are regulated through pathways mediated by jasmonic acid, H2 O2 , and Ca 2+ . These findings argue that (-)-loliolide functions as a common belowground signal mediating chemical defense in plants. Such perception-dependent plant chemical defenses will yield critical insights into belowground signaling interactions.

The Effect of the Stress-Signalling Mediator Triacontanol on Biochemical and Physiological Modifications in Dracocephalum forrestii Culture

Triacontanol (TRIA) has been reported to influence signal transduction in the crosstalk triggered by various stress factors. As a signal player, it is also known to affect many physiological processes, including enhancing the biosynthesis of secondary metabolites. Such knowledge can be used to direct or boost the production of bioactive secondary compounds without stress induction. Therefore, the aim of this study is to evaluate the use of TRIA as a factor stimulating the growth and production of bioactive compounds in the shoot culture of Dracocephalum forrestii. TRIA was applied at three concentrations (2.5, 5, and 10 µM), alone or in combination with phytohormones (6-benzylaminopurine and indole-3-acetic acid). After five weeks, growth and physiochemical parameters (chlorophyll content, antioxidant enzyme activity, and phenolic acid level) were determined. The results indicate that TRIA application significantly increased shoot dry weight, chlorophyll content, antioxidant enzyme activities (superoxide dismutase, peroxidase, and catalase), and total polyphenol level; it also influenced the multiplication ratio in combination with growth regulators. The greatest antioxidant enzyme activity was observed for 5 µM TRIA in hormone-free medium, while the most significant secondary metabolite production was obtained for phytohormone-containing medium supplemented with 10 µM TRIA: total phenolic acid content (19.4 mg/g dry weight) was twice that of the control. Hence, the TRIA application appears to be a valuable biotechnology technique for modifying plant metabolite production.

The Importance of Mycorrhizal Fungi in the Development and Secondary Metabolite Production of Echinacea purpurea and Relatives (Asteraceae): Current Research Status and Perspectives

The cultivation of Echinacea purpurea for commerce and obtaining high-quality plant material on a large scale remain a challenge for growers. Another challenge for the following decades is to create sustainable agriculture that meets society’s needs, has no environmental impact, and reduces the use of fertilizers and pesticides. The aims of this overview were: (1) to present the importance of the chemical compounds reported in E. purpurea; (1) to synthesize results about cultivation of the E. purpurea with arbuscular mycorrhizal fungi (AMF) and associated microorganisms; (2) to exemplify similar research with plants from the Asteraceae family, due to the limited number of published Echinacea studies; (3) to collect recent findings about how the inoculation with AMF affects gene expressions in the host plants; (4) to propose perspective research directions in the cultivation of E. purpurea, in order to increase biomass and economic importance of secondary metabolite production in plants. The AMF inocula used in the Echinacea experiments was mainly Rhizophagus irregularis. The studies found in the selected period (2012–2022), reported the effects of 21 AMFs used as single inocula or as a mixture on growth and secondary metabolites of 17 plant taxa from the Asteraceae family. Secondary metabolite production and growth of the economic plants were affected by mutualistic, symbiotic or parasitic microorganisms via upregulation of the genes involved in hormonal synthesis, glandular hair formation, and in the mevalonate (MVA), methyl erythritol phosphate (MEP) and phenylpropanoid pathways. However, these studies have mostly been carried out under controlled conditions, in greenhouses or in vitro in sterile environments. Since the effect of AMF depends on the variety of field conditions, more research on the application of different AMF (single and in various combinations with bacteria) to plants growing in the field would be necessary. For the identification of the most effective synergistic combinations of AMF and related bacterial populations, transcriptomic and metabolomic investigations might also be useful.

In vitro propagation for conservation and genetic fidelity of the near threatened Dimocarpus longan plant

BackgroundDimocarpus longan is a tropical tree that produces edible fruit. It is a neglected plant species that is listed as near threatened. In spite of its economic value, the propagation of longan cultivar using conventional methods is extremely difficult. The goal of this research is to produce and conserve this plant through in vitro propagation. ResultsIn order to form new shoots, sterilized shoot tip explants were cultured on Murashige and Skoog (MS) medium supplemented with benzyl adenine (BA) or 2-isobentenyl-adenine (2ip). For direct organogenesis, young leaves of new shoots were cultured on MS medium fortified with various concentrations of Thidiazuron (TDZ) or 6-(4-Hydroxy-3-methylbut-2-enylamino purine) (Zeatin). Gibbrellic acid (GA3) at different levels alone or in combination was used for shoot elongation. Also, indole-3-butyric acid (IBA) and naphthalene acetic acid (NAA) were used for root formation. MS medium supplemented with 1.00 mg/l 2ip was suitable for inducing axillary shoots from shoot tips (4.0 axillary shoots/explant). The highest significant 76% and numbers of adventitious buds from leaf base were achieved on MS medium containing 1.0 mg/l TDZ. These buds developed into the longest plantlets on GA3 at 3.0 mg/l and rooted well in ½MS containing 1.50 mg/l IBA plus 0.50 mg/l (NAA). About 70% in vitro plants were successfully acclimatized. The AFLP profile illustrated the genetic stability of gene expression action. The amplified fragment length polymorphisms (AFLPs) profile illustrated the progenies were extremely similar to the mother plants. According to our findings, MS medium containing 25 ppm salicylic acid (SA) and 5 ppm methyl jasmonate (MeJA) produced the highest percentage of apigenin in longan calli (77.09 and 2.637%, w/w). ConclusionA successful and efficient micropropagation protocol has been developed and described here for the first time, and it will be very useful for the clonal propagation and conservation of the near-threatened Dimocarpus longan plant. Micropropagated plants are genetically identical to the donor plant using the AFLP technique. The usefulness of salicylic acid and methyl jasmonate as elicitors for increasing in vitro production of secondary metabolites in plants is demonstrated in this work.