Positive regulatory role of R2R3 MYBs in terpene biosynthesis in Lilium‘Siberia’

Terpenoids are the main components contributing to the fragrance of Lilium‘Siberia’,and LiTPS2 plays a critical role in the biosynthesis of monoterpenoids.Although the major terpene synthases in Lilium‘Siberia’have been identified,how these TPS genes are transcriptionally regulated remains elusive in this distinguished flower.This study aimed to identify transcription factors that regulate the terpene synthesis in Lilium,and disclose the related underlying transcriptional regulation mechanism.In this study,we identified three R2R3-MYB TFs—LiMYB1,LiMYB305 and LiMYB330,which were involved in regulating the biosynthesis of terpenes in Lilium‘Siberia’.Quantitative real-time PCR showed spatial and temporal expression patterns consistent with the emission patterns of terpene compounds.When LiMYB1,LiMYB305 and LiMYB330were overexpressed in flowers,the release of some main monoterpenes,such as linalool and ocimene,as well as the expression of TPS genes,especially for LiTPS2,were enhanced.A virus-induced gene silencing(VIGS)assay showed that silencing these three LiMYBs decreased the level of monoterpenes by down-regulating the expression of the TPS genes.The yeast one-hybrid and transient expression assays indicated that all three LiMYBs could bind to and activate the promoter of LiTPS2.Moreover,the yeast two-hybrid assay verified that LiMYB1 could interact with LiMYB308 and LiMYB330,indicating their synergistic roles in the regulation of floral terpene biosynthesis.In general,these results indicated that LiMYB1,LiMYB305,and LiMYB330 might play essential roles in terpene biosynthesis in Lilium and would provide a new perspective for the transcriptional regulation of volatile terpenes in flowers.

Naturally Occurring Terpenes:A Promising Class of Organic Molecules to Address Influenza Pandemics

Since the olden times,infectious diseases have largely affected human existence.The newly emerged infections are excessively caused by viruses that are largely associated with mammal reservoirs.The casualties of these emergencies are significantly influenced by the way human beings interact with the reservoirs,especially the animal ones.In our review we will consider the evolutionary and the ecological scales of such infections and their consequences on the public health,with a focus on the pathogenic influenza A virus.The nutraceutical properties of fungal and plant terpene-like molecules will be linked to their ability to lessen the symptoms of viral infections and shed light on their potential use in the development of new drugs.New challenging methods in antiviral discovery will also be discussed in this review.The authors believe that pharmacognosy is the“wave of future pharmaceuticals”,as it can be continually produced and scaled up under ecofriendly requirements.Further diagnostic methods and strategies however are required to standardise those naturally occurring resources.

Plant Senescence: The Role of Volatile Terpene Compounds (VTCs)

Senescence is a natural, energy-dependent, physiological, developmental and an ecological process that is controlled by the plant’s own genetic program, allowing maximum recovery of nutrients from older organs for the survival of the plant, as such;it is classified as essential component of the growth and development of plants. In some cases, under one or many environmental stresses, senescence is triggered in plants. Despite many studies in the area, less consideration has been given to plant secondary metabolites, especially the role of VTCs on plant senescence. This review seeks to capture the biosynthesis and signal transduction of VTCs, the physiology of VTCs in plant development and how that is linked to some phytohormones to induce senescence. Much progress has been made in the elucidation of metabolic pathways leading to the biosynthesis of VTCs. In addition to the classical cytosolic mevalonic acid (MVA) pathway from acetyl-CoA, the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway, originating from glyceraldehyde-3-phosphate (GAP) and pyruvate, leads to the biosynthesis of isoprenoid precursors, isopentenyl diphosphate and dimethyl allyl diphosphate. VTCs synthesis and emission are believed to be tightly regulated by photosynthetic carbon supply into MEP pathway. Thus, under abiotic stresses such as drought, high salinity, high and low temperature, and low CO2 that directly affect stomatal conductance and ultimately biochemical limitation to photosynthesis, there has been observed induction of VTC synthesis and emissions, reflecting the elicitation of MEP pathway. This reveals the possibility of important function(s) of VTCs in plant defense against stress by mobilizing resources from components of plants and therefore, senescence. Our current understanding of the relationship between environmental responses and senescence mostly comes from the study of senescence response to phytohormones such as abscisic acid, jasmonic acid, ethylene and salicylic acid, which are extensively involved in response to various abiotic and biotic stresses. These stresses affect synthesis and/or signaling pathways of phytohormones to eventually trigger expression of stress-responsive genes, which in turn appears to affect leaf senescence. Comparison of plant response to stresses in relation to patterns of VTCs and phytohormones biosynthesis indicates a considerable crosstalk between these metabolic processes and their signal to plant senescence.

Frankincense derived heavy terpene cocktail boosting breast cancer cell(MDA-MB-231) death in vitro

Objective: To investigate the anti-cancer effect of frankincense derived heavy oil obtained by Soxhlet extraction method on breast cancer cells(MDA-MB-231), and to study its chemical profile using gas chromatography mass spectrometry analysis.Methods: Hexane was used to extract heavy oil from frankincense resin. Chemical profiling of heavy oil was done using Perkin Elmer Clarus GC system with mass spectrometer. MDA-MB-231 cells were treated with different dilutions(1:1 000, 1:1 500,1:1 750, 1:2 000, 1:2 250, 1:2 500, 1:2 750, 1:3 000, 1:3 250) of heavy oil for 24 h. The cells were observed by using light microscopy. Cell viability was measured by MTT assay.Results: Gas chromatography mass spectrometry chemical profiling of frankincense derived heavy oil revealed the presence of terpenes such as a-pinene(61.56%), a-amyrin(20.6%), b-amyrin(8.1%), b-phellandrene(1.47%) and camphene(1.04%). Heavy terpene cocktail induced significant MDA-MB-231 cell death at each concentration tested. Noticeably, very low concentration of Soxhlet derived heavy terpenes elicits considerable cytotoxicity on MDA-MB-231 cells compared to hydro distillated essential oil derived from frankincense resin.Conclusions: Extracting anti-cancer active principle cocktail by simple Soxhlet method is cost effective and less time consuming. Our in vitro anti-cancer data forms the rationale for us to test heavy terpene complex in breast cancer xenograft model in vivo. Furthermore, fractionation and developing frankincense heavy terpene based breast cancer drug is the major goal of our laboratory.

Evaluation of Terpenes’Degradation Rates by Rumen Fluid of Adapted and Non-adapted Animals

The aim of the present study was to evaluate terpenes degradation rate in the rumen fluid from adapted and non-adapted animals.Four castrated healthy animals,two rams and two bucks,were used.Animals were daily orally dosed for 2 weeks with 1 g of each of the following terpenes,α-pinene,limonene andβ-caryophyllene.At the end of each week,rumen fluid(RF)samples were assayed in vitro for their potential to degrade terpenes over time.For each animal,a 10 mL reaction medium(RM)at a ratio 1:9(v/v)was prepared and a terpenes solution at a concentration of 100μg/ml each,was added in each RM tube.Tubes were incubated at 39℃ under anaerobic conditions and their contents sampled at 0,2,4,8,21 and 24 h.RF could degrade terpenes as it was shown by the significantly(P<0.05)higher overall degradation rates.Individual terpene degradation rates,were significantly(P<0.05)higher in week 5 for limonene and marginally(P=0.083)higher also in week 5 forα-pinene.In conclusion,the findings of the present preliminary study suggest that terpenes can be degraded in the rumen fluid.

Terpenes of the Essential Oil from Ipomoea alba Leaf in Response to Herbivore and Mechanical Injuries

There is no doubt that the chemical composition of plants,including norvolatile and volatile compounds,is widely affected by abiotic and biotic stress.Plants are able to biosynthesize a variety of secondary metabolites against actions of natural enemies,such as herbivores,fungus,virus and bacteria.The present study revealed that the chemical compositions of leaf essential oils from Ipomoea alba underwent quantitative and qualitative alterations both when infested with the grasshopper Elaeochlora trilineata and mechanically damaged.Grasshopper attack and mechanical wounding induced the biosynthesis of nine volatile compounds in leaves of I.alba:cumene,α-ylangene,β-panasinsene,β-gurjunene aromadendrene,β-funebrene,spirolepechinene,cubenol and sclareolide.The amount of germacrene D(33.2%to 20.4%)decreased when the leaves were mechanically damaged;but when the leaves were attacked by a grasshopper,the germacrene D increased from 33.2%to 39.4%.The results showed that I.alba leaves clearly responded to abiotic and biotic stress and contribute to an understanding of plant responses to stress conditions.

Image Acquisition and Parameter Calculations for Optimization of the Automatic Identification of Terpenes in a Combined Laser Thin Film Extract

In this work, we propose an original approach to the thin-layer identification of secondary metabolites (terpenes) based on the acquisition of multicomponent images integrating terpenes to be identified. Its principle consists initially of segmentation by region of each component of the image based on the attribute tuples or colors of each region of the digital image. Then we proceeded to the calculations of region parameters such as standard deviation, entropy, average pixel color, eccentricity from an algorithm on the matlab software. These values allowed us to build a database. Finally, we built an algorithm for identifying secondary metabolites (terpenes) on the basis of these data. The relevance of our method of identifying or recognizing terpenes has been demonstrated compared to other methods, such as the one based on the calculation of frontal ratios which cannot discriminate between two terpenes having the same frontal ratio. The robustness of our method with respect to the identification of linalool, limonene was tested.

Effects of combined cannabidiol(CBD)and hops(Humulus lupulus)terpene extract treatment on RAW 264.7 macrophage viability and inflammatory markers

This study investigates the potential of cannabidiol(CBD),one major cannabinoid of the plant Cannabis sativa,alone and in combination with a terpene-enriched extract from Humulus lupulus(“Hops 1”),on the LPS-response of RAW 264.7 macrophages as an established in vitro model of inflammation.With the present study,we could support earlier findings of the anti-inflammatory potential of CBD,which showed a dose-dependent[0-5μM]reduction in nitric oxide and tumor necrosis factor-alpha(TNF-α)released by LPS-stimulated RAW 264.7 macrophages.Moreover,we observed an additive anti-inflammatory effect after combined CBD[5μM]and hops extract[40μg/mL]treatment.The combination of CBD and Hops 1 showed effects in LPS-stimulated RAW 264.7 cells superior to the single sub-stance treatments and akin to the control hydrocortisone.Furthermore,cellular CBD uptake increased dose-depend-ently in the presence of terpenes from Hops 1 extract.The anti-inflammatory effect of CBD and its cellular uptake positively correlated with terpene concentration,as indicated by comparison with a hemp extract containing both CBD and terpenes.These findings may contribute to the postulations for the so-called“entourage effect”between cannabinoids and terpenes and support the potential of CBD combined with phytomolecules from a non-cannabi-noid source,such as hops,for the treatment of inflammatory diseases.

The chromosome-level genome of double-petal phenotype jasmine provides insights into the biosynthesis of floral scent

Jasmine(Jasminum sambac Aiton)is a well-known cultivated plant species for its fragrant flowers used in the perfume industry and cosmetics.However,the genetic basis of its floral scent is largely unknown.In this study,using PacBio,Illumina,10×Genomics and highthroughput chromosome conformation capture(Hi-C)sequencing technologies,a high-quality chromosome-level reference genome for J.sambac was obtained,exploiting a double-petal phenotype cultivar‘Shuangbanmoli’(JSSB).The results showed that the final assembled genome of JSSB is 580.33 Mb in size(contig N50=1.05 Mb;scaffold N50=45.07 Mb)with a total of 39618 predicted protein-coding genes.Our analyses revealed that the JSSB genome has undergone an ancient whole-genome duplication(WGD)event at 91.68 million years ago(Mya).It was estimated that J.sambac diverged from the lineage leading to Olea europaea and Osmanthus fragrans about 28.8 Mya.On the basis of a combination of genomic,transcriptomic and metabolomic analyses,a range of floral scent volatiles and genes were identified involved in the benzenoid/phenylpropanoid and terpenoid biosynthesis pathways.The results provide new insights into the molecular mechanism of its fragrance biosynthesis in jasmine.

Recently duplicated sesterterpene(C25) gene clusters in Arabidopsis thaliana modulate root microbiota

Land plants co-speciate with a diversity of continually expanding plant specialized metabolites(PSMs) and root microbial communities(microbiota).Homeostatic interactions between plants and root microbiota are essential for plant survival in natural environments.A growing appreciation of microbiota for plant health is fuelling rapid advances in genetic mechanisms of controlling microbiota by host plants.PSMs have long been proposed to mediate plant and single microbe interactions.However,the effects of PSMs,especially those evolutionarily new PSMs,on root microbiota at community level remain to be elucidated.Here,we discovered sesterterpenes in Arabidopsis thaliana,produced by recently duplicated prenyltransferase-terpene synthase(PT-TPS) gene clusters,with neo-functionalization.A single-residue substitution played a critical role in the acquisition of sesterterpene synthase(sesterTPS) activity in Brassicaceae plants.Moreover,we found that the absence of two root-specific sesterterpenoids,with similar chemical structure,significantly affected root microbiota assembly in similar patterns.Our results not only demonstrate the sensitivity of plant microbiota to PSMs but also establish a complete framework of host plants to control root microbiota composition through evolutionarily dynamic PSMs.

Cytotoxic terpenes from Abies sibirica

One new and 16 known compounds were isolated from Abies sibirica. Their structures were assigned mainly on the basis of NMR and MS spectroscopic data. In bioassay for anti-proliferative activity against four human tumor cells, compound 7 exhibited selective anti-proliferative activity against COLO-205 tumor cell with an IC50 value of 0.9 μg/mL.

Molecular Basis for Sesterterpene Diversity Produced by Plant Terpene Synthases

Class I terpene synthase(TPS)generates bioactive terpenoids with diverse backbones.Sesterterpene synthase(sester-TPS,C25),a branch of class I TPSs,was recently identified in Brassicaceae.However,the catalytic mechanisms of sester-TPSs are not fully understood.Here,we first identified three nonclustered functional sester-TPSs(AtTPS06,AtTPS22,and AtTPS29)in Arabidopsis thaliana.AtTPS06 utilizes a type-B cyclization mechanism,whereas most other sester-TPSs produce various sesterterpene backbones via a type-A cyclization mechanism.We then determined the crystal structure of the AtTPS18–FSPP complex to explore the cyclization mechanism of plant sester-TPSs.We used structural comparisons and site-directed mutagenesis to further elucidate the mechanism:(1)mainly due to the outward shift of helix G,plant sester-TPSs have a larger catalytic pocket than do mono-,sesqui-,and di-TPSs to accommodate GFPP;(2)type-A sester-TPSs have more aromatic residues(five or six)in their catalytic pocket than classic TPSs(two or three),which also determines whether the type-A or type-B cyclization mechanism is active;and(3)the other residues responsible for product fidelity are determined by interconversion of AtTPS18 and its close homologs.Altogether,this study improves our understanding of the catalytic mechanism of plant sester-TPS,which ultimately enables the rational engineering of sesterterpenoids for future applications.

Occurrence and biosynthesis of plant sesterterpenes (C25), a new addition to terpene diversity

Terpenes,the largest group of plant-specialized metabolites,have received considerable attention for their highly diverse biological activities.Monoterpenes(C10),sesquiterpenes(C15),diterpenes(C20),and triterpenes(C30)have been extensively investigated at both the biochemical and molecular levels over the past two decades.Sesterterpenes(C25),an understudied terpenoid group,were recently described by plant scientists at the molecular level.This review summarizes the plant species that produce sesterterpenes and describes recent developments in the field of sesterterpene biosynthesis,placing a special focus on the catalytic mechanism and evolution of geranylfarnesyl diphosphate synthase and sesterterpene synthase.Finally,we propose several questions to be addressed in future studies,which may help to elucidate sesterterpene metabolism in plants.

Discovery and analysis of a new class of triterpenes derived from hexaprenyl pyrophosphate

Triterpenes are derived from squalene or oxidosqualene.However,a new class of triterpenes derived from hexaprenyl pyrophosphate has been recently discovered,formed by a new family of chimeric class I triterpene synthases.The cyclization mechanisms of triterpenes were elucidated by isotopic labeling and protein structural analyses,which helps understand the biosynthesis of triterpenes in nature.

A Genome-Wide Scenario of Terpene Pathways in Self-pollinated Artemisia annua

Scenarios of genes to metabolites in Artemisia annua remain uninvestigated. Here, we report the use of an integrated approach combining metabolomics, transcriptomics, and gene function analyses to charac- terize gene-to-terpene and terpene pathway scenarios in a self-pollinating variety of this species. Eightyeight metabolites including 22 sesquiterpenes （e.g., artemisinin）, 26 monoterpenes, two triterpenes, one diterpene and 38 other non-polar metabolites were identified from 14 tissues. These metabolites were differentially produced by leaves and flowers at lower to higher positions. Sequences from cDNA libraries of six tissues were assembled into 18 871 contigs and genome-wide gene expression profiles in tissues were strongly associated with developmental stages and spatial specificities. Sequence mining identified 47 genes that mapped to the artemisinin, non-amorphadiene sesquiterpene, monoterpene, triterpene, 2-C- methyl-D-erythritol 4-phosphate and mevalonate pathways. Pearson correlation analysis resulted in network integration that characterized significant correlations of gene-to-gene expression patterns and gene expression-to-metabolite levels in six tissues simultaneously. More importantly, manipulations of amorpha-4,11-diene synthase gene expression not only affected the activity of this pathway toward artemisinin, artemisinic acid, and arteannuin b but also altered non-amorphadiene sesquiterpene and genome-wide volatile profiles. Such gene-to-terpene landscapes associated with different tissues are fundamental to the metabolic engineering of artemisinin.

Role of terpenes from aphid-infested potato on searching and oviposition behavior of Episyrphus balteatus

To cope with pathogen and insect attacks, plants develop different mechanisms of defence, in both direct （physical and chemical） and indirect ways （attractive volatiles to entomophagous beneficials）. Plants are then able to express traits that facilitate ＂top-down＂ control of pests by attracting herbivore predators. Here we investigate the indirect defence mechanism of potato plants by analyzing the volatile patterns of both healthy and aphid- infested plants. Important changes in the emitted terpene pattern by the Myzus persicae infested host plant were observed. Using Solid Phase MicroExtraction （SPME） and GC-MS, the （E）-fl-farnesene （EBF） appeared to be emitted by aphid-infested potato and not by healthy plants. To assess the infochemical role of these volatile releases after aphid damage on the aphidophagous predators Episyrphus balteams, the hoverfly foraging behavior was assessed using the Observer 5.0 software （Noldus, Wageningen, The Netherlands）. Aphidfree potato plants were also used as a control volatile source in the predator behavioral study. While aphid-infested plants induced efficient searching and acceptation behaviors leading to egg-laying, no kairomonal effect of healthy potato plants was observed, leading to longer immobility durations and shorter searching periods in the net cage. High oviposition rate of E. balteatus was observed when aphid-infested potato was used （mean of 48.9 eggs per laying and per female）. On the other hand, no egg was produced by the hoverfly on healthy aphid-free plants. The E. balteatus foraging and reproductive behaviors according to the volatile emission from aphid-infested plants are discussed in relation to the potential use of active infochemical molecules in integrated aphid pest management.

The chromosome-scale genome of Phoebe bournei reveals contrasting fates of terpene synthase (TPS)-a and TPS-b subfamilies

Terpenoids,including aromatic volatile monoterpenoids and sesquiterpenoids,function in defense against pathogens and herbivores.Phoebe trees are remarkable for their scented wood and decay resistance.Unlike other Lauraceae species investigated to date,Phoebe species predominantly accumulate sesquiterpenoids instead of monoterpenoids.Limited genomic data restrict the elucidation of terpenoid variation and functions.Here,we present a chromosome-scale genome assembly of a Lauraceae tree,Phoebe bournei,and identify 72 full-length terpene synthase(TPS)genes.Genome-level comparison shows pervasive lineage-specific duplication and contraction of TPS subfamilies,which have contributed to the extreme terpenoid variation within Lauraceae species.Although the TPS-a and TPS-b subfamilies were both expanded via tandem duplication in P.bournei,more TPS-a copies were retained and constitutively expressed,whereas more TPS-b copies were lost.The TPS-a genes on chromosome 8 functionally diverged to synthesize eight highly accumulated sesquiterpenes in P.bournei.The essential oil of P.bournei and its main component,b-caryophyllene,exhibited antifungal activities against the three most widespread canker pathogens of trees.The TPS-a and TPS-b subfamilies have experienced contrasting fates over the evolution of P.bournei.The abundant sesquiterpenoids produced by TPS-a proteins contribute to the excellent pathogen resistance of P.bournei trees.Overall,this study sheds light on the evolution and adaptation of terpenoids in Lauraceae and provides valuable resources for boosting plant immunity against pathogens in various trees and crops.

The jasmonate-induced bHLH gene SlJIG functions in terpene biosynthesis and resistance to insects and fungus

Jasmonic acid(JA)is a key regulator of plant defense responses.Although the transcription factor MYC2,the master regulator of the JA signaling pathway,orchestrates a hierarchical transcriptional cascade that regulates the JA responses,only a few transcriptional regulators involved in this cascade have been described.Here,we identified the basic helix-loop-helix(bHLH)transcription factor gene in tomato(Solanum lycopersicum),METHYL JASMONATE(MeJA)-INDUCED GENE(SlJIG),the expression of which was strongly induced by MeJA treatment.Genetic and molecular biology experiments revealed that SlJIG is a direct target of MYC2.SlJIG knockout plants generated by gene editing had lower terpene contents than the wild type from the lower expression of TERPENE SYNTHASE(TPS)genes,rendering them more appealing to cotton bollworm(Helicoverpa armigera).Moreover,SlJIG knockouts exhibited weaker JA-mediated induction of TPSs,suggesting that SlJIG may participate in JA-induced terpene biosynthesis.Knocking out SlJIG also resulted in attenuated expression of JA-responsive defense genes,which may contribute to the observed lower resistance to cotton bollworm and to the fungus Botrytis cinerea.We conclude that SlJIG is a direct target of MYC2,forms a MYC2-SlJIG module,and functions in terpene biosynthesis and resistance against cotton bollworm and B.cinerea.

The Contents of Terpene Trilactone and Flavonoid in Leaves of Seedlings from Ancient Female Ginkgo Trees in China

Flavonoids and terpene trilactones, especially, ginkgo flavonglycosides, ginkgolides and bilobalides in leaves of ginkgo trees, need to be studied for effective application of these active components with high medical and health-care values. This study was aimed to provide scientific bases for genealogies selection and harvest season confirmation for Ginkgo biloba. A high-performance liquid chromatographic method(HPLC-ELSD)was developed to determine the contents of terpene trilactone and flavonoid of 36 ancient G. biloba genealogies from 19 provinces in China.The study indicated that the content gradually increased from April to August, and thereafter declined. Analysis of variance indicated that the contents of terpene trilactone, flavonoids, and their respective components had significant difference among 36 genealogies. The cluster analysis showed that No. 72(Xing'an, Guangxi), No. 58(Youyang, Chongqing), No. 82(Rugao, Jiangsu), No. 123(Huixian, Gansu), No. 99(Dujun, Guizhou),No. 10(Tai'an, Shandong) and No. 133(Mentougou, Beijing) genealogies have higher content of terpene trilactone and flavonoid. These results can help us to select superior variety containing high content of terpene trilactone and flavonoid.

SNARE-RNAi Results in Higher Terpene Emission from Ectopically Expressed Caryophyllene Synthase in Nicotiana benthamiana

Plants produce numerous terpenes and much effort has been dedicated to the identification and charac- terization of the terpene biosynthetic genes. However, little is known about how terpenes are transported within the cell and from the cell into the apoplast. To investigate a putative role of vesicle fusion in this pro- cess, we used Agrobacterium tumefaciens-mediated transient coexpression in Nicotiana benthamiana of an MtVAMP721e-RNAi construct （Vi） with either a caryophyllene synthase or a linalool synthase, respec- tively. Headspace analysis of the leaves showed that caryophyllene or linalool emission increased about five-fold when N. benthamiana VAMP72 function was blocked. RNA sequencing and protein ubiquitination analysis of the agroinflltrated N. benthamiana leaf extracts suggested that increased terpene emissions may be attributed to proteasome malfunction based on three observations： leaves with TPS＋Vi showed （1） a higher level of a DsRed marker protein, （2） a higher level of ubiquitinated proteins, and （3） coordinated induced expression of multiple proteasome genes, presumably caused by the lack of proteasome- mediated feedback regulation. However, caryophyllene or linalool did not inhibit proteasome-related pro- tease activity in the in vitro assays. While the results are not conclusive for a role of vesicle fusion in terpene transport, they do show a strong interaction between inhibition of vesicle fusion and ectopic expression of certain terpenes. The results have potential applications in metabolic engineering.