Effects of Waterlogging Stress on the Physiological Characteristics and Secondary Metabolites of Herbaceous Peony (<i>Paeonia lactiflora</i>Pall.)

Herbaceous peony is an ornamental plant with medicinal properties. Waterlogging can affect its yield and quality as it grows and matures. In this study, we subjected “Taohuafeixue”, “Yangfeichuyu” and “Hongxiuqiu” herbaceous peony varieties to a simulated waterlogging stress treatment and investigated the effects of waterlogging on their physiological characteristics and the secondary metabolite contents in their leaves and roots. Short-term waterlogging caused the leaves to turn yellow or red and the roots to turn black. The stele and the cell wall of the endothelial cells thickened, and the cortical cells enlarged. Waterlogging did not significantly change plant height, leaf length, and leaf area;however, it significantly decreased the root-shoot ratio of “Yangfeichuyu” and “Hongxiuqiu” varieties. The activity of antioxidant enzymes and the content of osmotic regulators increased under waterlogging. After short-term waterlogging stress treatment, the content of paeoniflorin and albiflorin increased in the roots of “Taohuafeixue” and “Yangfeichuyu”, and the content of benzoylpaeoniflorin increased in the root of “Hongxiuqiu”. The content of gallic acid and total flavonoids increased in the leaves of “Taohuafeixue” and “Yangfeichuyu”. After the waterlogging, paeoniflorin and benzoylpaeoniflorin increased in the autumn root of “Hongxiuqiu”. This study expands our knowledge about the medicinal properties of herbaceous peony and informs about its production and cultivation under waterlogged conditions.

Phytochemical Analysis and Bioactivity Screening of Primary and Secondary Metabolic Products of Medicinal Plants in the Valleys of Medina Region Saudi Arabia

Medicinal plants are highly valued for their active compounds. These plants can be used in various fields and preservation of these plants in their environment. The present study aimed to screen medicinal plants used in traditional medicine in Medina valleys for the presence of metabolites, and to answer the following question: is the ethnomedicinal importance of medicinal plants used in Medina valleys conform to their primary and secondary metabolite content. Eight plants (Pulicaria incise, Heliotropium arbainense, Commicarpus grandiflorus, Rumex vesicarius, Senna alexandrina, Rhazya stricta, Withania somnifera and Asphodelus fistulosus) were collected from the Medina valleys and were biochemically analyzed to determine the different compounds after leaves extraction analyzed statistically to clarify the content of primary compounds. The chemical compounds in the most active fraction were determined using quantitative phytochemical and gas chromatography-mass spectrometry (GC/MS) analytical methods, comparing the mass spectra of the GC/MS identified compounds with those of the Center of Excellence in Environmental Studies (CEES) database library. The result showed 16 aroma compounds representing the GC/MS analysis revealed the presence of various compounds like 4,4-Dimethyl octane, 5H-1-Pyrindine and 1,3- Cyclopentadiene, 1,2,5,5-tetramethyl- in the ethanolic extract of Pulicaria incisa. The most prevalent plants were Pulicaria incisa, Senna alexandrina and Heliotropium arbainense the study plants have high content of protein. There is a need to focus phytochemical screening on ethnobotanical studies to complete research into traditional medicine which leads to the discovery of new drugs.

Sugarcane leaves-derived polyphenols alleviate metabolic syndrome and modulate gut microbiota of ob/ob mice

Sugarcane leaves-derived polyphenols(SLP)have been demonstrated to have diverse health-promoting benefits,but the mechanism of action has not been fully elucidated.This study aimed to investigate the anti-metabolic disease effects of SLP and the underlying mechanisms in mice.In the current study,we prepared the SLP mainly consisting of three flavonoid glycosides,three phenol derivatives,and two lignans including one new compound,and further demonstrated that SLP reduced body weight gain and fat accumulation,improved glucose and lipid metabolism disorders,ameliorated hepatic steatosis,and regulated short-chain fatty acids(SCFAs)production and secondary bile acids metabolism in ob/ob mice.Notably,SLP largely altered the gut microbiota composition,especially enriching the commensal bacteria Akkermansia muciniphila and Bacteroides acidifaciens.Oral gavage with the above two strains ameliorated metabolic syndrome(MetS),regulated secondary bile acid metabolism,and increased the production of SCFAs in high-fat diet(HFD)-induced obese mice.These results demonstrated that SLP could be used as a prebiotic to attenuate MetS via regulating gut microbiota composition and further activating the secondary bile acids-mediated gut-adipose axis.

Cell Apoptosis Induced by Oligosaccharide in Suspension Cultures of Taxus chinensis

Taxol production of Taxus chinensis (Pilger) Rehd. var. mairei (Lemee et Lévl.) Cheng et L. K. Fu induced by oligosaccharide from Fusarium oxysporum f. vasinfectum (Atkinson) Snyder et Hansen was studied in suspension cultures, and it was found that oligosaccharide triggered cell apoptosis. Under transmission electron microscope the following morphological changes were observed: cell shrinkage, condensation of cytoplasm, nuclear fragmentation, and the increase of high electron density bodies in vacuole in great quantity. In oligosaccharide_treated cells, agarose gel electrophoresis revealed that DNA was digested into oligonucleosomal fragments that were times of 200 bp appearing as DNA ladders. Control cells were in normal physiological state, they were intact, abundant in organelle and with integral nucleus DNA, and the rate of taxol biosynthesis in these cells was very low. After the oligosaccharide to the culture system, the defense system of cells was elicited and the secondary metabolism was strengthened, i.e. phenolics were accumulated in the medium, the activity of polyphenol oxidase (PPO) was increased quickly and secondary wall of cells was thickened. The activity of L _phenylalanine ammonia lyase (PAL), the critical enzyme of the phenylpropanoid pathway, was increased promptly 1 h after elicitation. The rate of taxol production was improved sharply and the maximal taxol concentration at 72 h was six times that of control. Appearance of cell apoptosis was accompanied with the highest concentration of taxol in suspension cultures.

Effects of phenolic acids on soil nitrogen mineralization over successive rotations in Chinese fir plantations

Phenolic acids are secondary metabolites of plants that significantly affect nutrient cycling processes.To investigate such effects,the soil available nitrogen(N)content,phenolic acid content,and net N mineralization rate in three successive rotations of Chinese fir plantations in subtropical China were investigated.Net N mineralization and nitrification rates in soils treated with phenolic acids were measured in an ex situ experiment.Compared with first-rotation plantations(FCP),the contents of total soil nitrogen and nitrate in second(SCP)-and third-rotation plantations(TCP)decreased,and that of soil ammonium increased.Soil net N mineralization rates in the second-and third-rotation plantations also increased by 17.8%and 39.9%,respectively.In contrast,soil net nitrification rates decreased by 18.0%and 25.0%,respectively.The concentrations of total phenolic acids in the FCP soils(123.22±6.02 nmol g^-1)were 3.0%and 17.9%higher than in the SCP(119.68±11.69 nmol g^-1)and TCP(104.51±8.57 nmol g^-1,respectively).The total content of phenolic acids was significantly correlated with the rates of net soil N mineralization and net nitrification.The ex situ experiment showed that the net N mineralization rates in soils treated with high(HCPA,0.07 mg N kg^-1 day^-1)and low(LCPA,0.18 mg N kg^-1 day^-1)concentrations of phenolic acids significantly decreased by 78.6%and 42.6%,respectively,comparing with that in control(0.32 mg N kg^-1 day^-1).Soil net nitrification rates under HCPA and LCPA were significantly higher than that of the control.The results suggested that low contents of phenolic acids in soil over successive rotations increased soil net N mineralization rates and decreased net nitrification rates,leading to consequent reductions in the nitrate content and enhancement of the ammonium content,then resulting in enhancing the conservation of soil N of successive rotations in Chinese fir plantation.

A study on JA-and BTH-induced resistance of Rosa rugosa‘Plena’to powdery mildew(Sphaerotheca pannosa)

Different concentrations of jasmonic acid(JA)and benzothiadiazole(BTH) were sprayed on 2-year-old Rosa rugosa‘Plena’ seedlings. The induced resistance of JA and BTH to Sphaerotheca pannosa(Wallr.) and the changes of their related physiological indices were investigated. Results showed that JA and BTH treatments had inhibitory impacts on S. pannosa infection. The optimal concentration of JA and BTH was 0.5 mmol/L for the disease-resistance induction of the leaves, its inductive effect was up to 66.36% for BTH and 54.49% for JA. Our results confirmed that exogenous JA and BTH significantly improved R. rugose ‘Plena’ resistance to S. pannosa. When treated with JA and BTH, activities of the three defense enzymes(POD, PPO, and PAL) increased significantly.Contents of total phenolics, flavonoids, and lignin also increased significantly. It is inferred from these results that exogenous JA and BTH could improve the resistance of R.rugose ‘Plena’ to S. pannosa through enhancing activities of the defensive enzymes and accumulation of secondary metabolites in the leaves.

Overexpression of IbPAL1 promotes chlorogenic acid biosynthesis in sweetpotato

Sweetpotato[Ipomoea batatas(L.)Lam.],a food crop with both nutritional and medicinal uses,plays essential roles in food security and health-promoting.Chlorogenic acid(CGA),a polyphenol displaying several bioactivities,is distributed in all edible parts of sweetpotato.However,little is known about the specific metabolism of CGA in sweetpotato.In this study,IbPAL1,which encodes an endoplasmic reticulum-localized phenylalanine ammonia lyase(PAL),was isolated and characterized in sweetpotato.CGA accumulation was positively associated with the expression pattern of IbPAL1 in a tissue-specific manner,as further demonstrated by overexpression of IbPAL1.Overexpression of IbPAL1 promoted CGA accumulation and biosynthetic pathway genes expression in leaves,stimulated secondary xylem cell expansion in stems,and inhibited storage root formation.Our results support a potential role for IbPAL1 in sweetpotato CGA biosynthesis and establish a theoretical foundation for detailed mechanism research and nutrient improvement in sweetpotato breeding programs.

Recent Advances on Key Enzyme Genes in Metabolic Pathways Related to the Synthesis of Aroma Compounds in Tobacco

This article summarized three main kinds of metabolic pathways related to the synthesis of aroma compounds in plants, concluded the roles and expres- sion patterns of key enzyme genes catalyzing the formation of major intermediate products in phenylpropanoid metabolic pathway, isoprene metabolic pathway and alkaloid biosynthetic pathway respectively, highlighted the latest developments of these key enzyme genes in tobacco, and accordingly proposed that in-depth study at the protein level and analysis of metabolic network interaction should be carried out in tobacco besides the expression regulation and transgenic crop improvement at the genetic level. Based on the above analysis, further improvement of tobacco aroma quality through metabolic engineering and its application prospect in agricultural production were prospected.

Elevated CO2 offsets the alteration of foliar chemicals(n-icosane,geranyl acetate,and elixene)induced by elevated O3 in three taxa of O3-tolerant eucalypts

Eucalypts are important forest resources in southwestern China,and may be tolerant to elevated ground-level ozone(O3)concentrations that can negatively affect plant growth.High CO2 may offset O3-induced effects by providing excess carbon to produce secondary metabolites or by inducing stomatal closure.Here,the effects of elevated CO2 and O3 on leaf secondary metabolites and other defense chemicals were studied by exposing seedlings of Eucalyptus globulus,E.grandis,and E.camaldulensis×E.deglupta to a factorial combination of two levels of O3(<10 nmol mol^(−1)and 60 nmol mol^(−1))and CO2(ambient:370μmol mol^(−1)and 600μmol mol^(−1))in open-top field chambers.GC-profiles of leaf extracts illustrated the effect of elevated O3 and the countering effect of high CO2 on compounds in leaf epicuticular wax and essential oils,i.e.,n-icosane,geranyl acetate and elixene,compounds known as a first-line defense against insect herbivores.n-Icosane may be involved in tolerance mechanisms of E.grandis and the hybrid,while geranyl acetate and elixene in the tolerance of E.globulus.Elevated O3 and CO2,singly or in combination,affected only leaf physiology but not biomass of various organs.Elevated CO2 impacted several leaf traits,including stomatal conductance,leaf mass per area,carbon,lignin,n-icosane,geranyl acetate and elixene.Limited effects of elevated O3 on leaf physiology(nitrogen,n-icosane,geranyl acetate,elixene)were commonly offset by elevated CO2.We conclude that E.globulus,E.grandis and the hybrid were tolerant to these O3 and CO2 treatments,and n-icosane,geranyl acetate and elixene may be major players in tolerance mechanisms of the tested species.

Effects of Small Water Clusters on the Growth and Microcystin Production of Microcystis aeruginosa

Mierocystis aeruginosa FACHB 905 was used as a model organism to study the ellects oI small water clusters （SWCs） on the growth and microcystin （MC） production of toxic cyanobacteria. The results showed that SWCs were able to stimulate the growth of Microcystis aeruginosa, which resulted in increased cell numbers and higher specific growth rates after a 30-d treatment. The cell morphology indicated that Microcystis aeruginosa was in a better state of growth, and it was more prone to divide in SWCs than in normal water clusters. The SWCs treatment up-regulated MC synthesis and exudation in 10 d in Microcystis aeruginosa, and the intra-cellular MC content de- creased after the 20th day subsequently. Moreover, the cellular photosynthetic pigment contents were temporarily stimulated by SWCs. A possible reason is that SWCs stimulated the growth by promoting photosynthesis, whereas the increased MC production was relevant to pigment contents.

2-Oxoglutarate-dependent dioxygenases in plants:biosynthesis,mechanism and evolution

2-Oxoglutarate(2OG)-dependent dioxygenases(2-ODDs)are omnipresent iron-containing non-heme enzymes that catalyze various oxidation-reduction reactions in plant growth and development,nucleic acid modification and secondary metabolism.We systematically summarized recent research on the oxidative modifications of plant 2-ODDs and related enzymes,their vital importance in the biosynthesis of plant special metabolites,and their catalytic specificity/flexibility,and discussed the potential of 2-ODD as a new approach for the identification of pivotal genes and the elucidation of biosynthetic pathway.

Efficient Production of δ-Guaiene, an Aroma Sesquiterpene Compound Accumulated in Agarwood, by Mevalonate Pathway-Engineered Escherichia coli Cells

Mevalonate pathway for isoprenoid biosynthesis was constructed in Escherichia coli cells by the transformation with a gene cluster isolated from Streptomyces sp., and farnesyl diphosphate synthase and δ-guaiene synthase genes were coexpressed in this strain. This transformant was capable of liberating an appreciable amount of δ-guaiene, an aroma sesquiterpene compound accumulated in agarwood, and its concentration was elevated to more than 30 μg/ml culture by the incubation with mevalonolactone as an isoprene precursor in a nutrient-enriched Terrific broth. Coexpression of type 1 isopentenyl diphosphate isomerase plus acetoacetyl-CoA ligase genes also enhanced δ-guaiene production, and the concentration of the compound was approximately 38 - 42 μg/ml culture in the presence of mevalonolactone or lithium acetoacetate. These results clearly indicate that mevalonate pathway-engineered E. coli cells showed an appreciable δ-guaiene producing activity in the en- riched medium in the presence of appropriate isoprene precursors.

Genus-specific secondary metabolome in Allokutzneria and Kibdelosporangium

Rare actinomycete genera are highly recognized as a promising source of structurally diverse and bioactive natural products.Among these genera,Allokutzneria and Kibdelosporangium are two phylogenetically closely related and have been reported to encode some valuable biosynthetic enzymes and secondary metabolites.However,there is currently no relevant systematic research available to outline the linkage of genomic and metabolomics for specific secondary metabolites in these two promising genera.In this study,we first investi-gated the genus-specific secondary metabolic potential in Allokutzneria and Kibdelosporangium by comparing the diversity and novelty of their secondary metabolite biosynthetic gene clusters(BGCs).The specific secondary metabolites produced by two representative strains of these genera were comprehensively investigated using untargeted metabolomics techniques.The findings unveiled that the majority(95.4%)of the gene cluster families(GCFs)encoded by Allokutzneria and Kibdelosporangium were genus-specific,including NRPS GCFs encoding siderophores.The untargeted metabolomics analysis revealed that the metabolic profiles of two representative strains exhibit extensive specificity,with the culture medium having a big impact on the metabolic profiles.Besides,an MS-cluster featuring a series of hydroxamate-type siderophores was identified from Allokutzneria albata JCM 9917,with two of them,including a novel one(N-deoxy arthrobactin A),being experimentally validated.The present study offers valuable insights for the targeted discovery of genus-specific natural products from microorganisms.

Transcriptional Regulation of Plant Secondary Metabolism

Plant secondary metabolites play critical roles in plant-environment interactions. They are synthesized in different organs or tissues at particular developmental stages, and in response to various environmental stimuli, both biotic and abiotic. Accordingly, corresponding genes are regulated at the transcriptional level by multiple transcription factors. Several families of transcription factors have been identified to participate in controlling the biosynthesis and accumulation of secondary metabolites. These regulators integrate internal （often developmental） and external signals, bind to corresponding cis-elements -- which are often in the promoter regions -- to activate or repress the expression of enzyme-coding genes, and some of them interact with other transcription factors to form a complex. In this review, we summarize recent research in these areas, with an emphasis on newly-identified transcription factors and their functions in metabolism regulation.

Secondary metabolism in simulated microgravity and space flight

Space flight experiments have suggested that microgravity can affect cellular processes in microorganisms.To simulate the microgravity environment on earth,several models have been developed and applied to examine the effect of microgravity on secondary metabolism.In this paper,studies of effects of space flight on secondary metabolism are exemplified and reviewed along with the advantages and disadvantages of the current models used for simulating microgravity.This discussion is both significant and timely to researchers considering the use of simulated microgravity or space flight to explore effects of weightlessness on secondary metabolism.

Germplasm resources and secondary metabolism regulation in Reishi mushroom(Ganoderma lucidum)

Ganoderma lucidum is a valuable medical macrofungus with a myriad of diverse secondary metabolites,in which triterpenoids are the major constituents.This paper introduced the germplasm resources of genus Ganoderma from textual research,its distribution and identification at the molecular level.Also we overviewed G.lucidum in the components,the biological activities and biosynthetic pathways of ganoderic acid,aiming to provide scientific evidence for the development and utilization of G.lucidum germplasm resources and the biosynthesis of ganoderic acid.

Genetic manipulation and tools in myxobacteria for the exploitation of secondary metabolism

Myxobacteria are famous for their capacity for social behavior and natural product biosynthesis.The unique sociality of myxobacteria is not only an intriguing scientific topic but also the main limiting factor for their ma-nipulation.After more than half a century of research,a series of genetic techniques for myxobacteria have been developed,rendering these mysterious bacteria manipulable.Here,we review the advances in genetic manipu-lation of myxobacteria,with a particular focus on the exploitation of secondary metabolism.We emphasize the necessity and urgency of constructing the myxobacterial chassis for synthetic biology research and the exploita-tion of untapped secondary metabolism.

COP9 signalosome subunit PfCsnE regulates secondary metabolism and conidial formation in Pestalotiopsis fici

The COP9 signalosome(CSN) is a highly conserved multiprotein complex in all eukaryotes and involved in regulation of organism development. In filamentous fungi, several lines of evidence indicate that fungal development and secondary metabolism(SM) are mediated by the fifth subunit of CSN, called CsnE. Here we uncover a connection with CsnE and conidial formation as well as SM regulation in the plant endophytic fungus Pestalotiopsis fici. A homology search of the P. fici genome with CsnE, involved in sexual development and SM in Aspergillus nidulans, identified PfCsnE. Deletion of PfcsnE resulted in a mutant that stopped conidial production, but the conidia are recovered in a PfcsnE complemented strain. This indicates that PfCsnE is required for the formation of conidia. Secondary metabolite analysis demonstrated that the ΔPfcsnE strain produced more chloroisosulochrin, less ficiolide A production in comparison to wild type(WT). Transcriptome analysis of WT andΔPfcsnE strains indicated that PfcsnE impacts the expression levels of 8.37% of 14,797 annotated genes. Specifically, nine biosynthetic gene clusters(BGCs) were up-regulated and three BGCs were down-regulated by PfCsnE. Our results suggest that PfCsnE plays major roles in SM regulation and conidial development in P. fici.

Phytohormones Jasmonic Acid,Salicylic Acid,Gibberellins,and Abscisic Acid are Key Mediators of Plant Secondary Metabolites

Until recently,many studies on the role of phytohormones in plant secondary metabolism focused on jasmonic acid(JA),salicylic acid(SA),gibberellins(GA),and abscisic acid(ABA).It is now clear that phytohormone?induced regulation of signaling occurs via regulation of the biosynthetic pathway genes at the transcriptional level or through posttranslational regulation,or an increase in secondary metabolite deposition(e.g.,trichomes).Here,we summarize recent advances,updating the current reports on the molecular machinery of phytohormones JA,SA,GA,and ABA involved in plant secondary metabolites.This review emphasizes the differences and similarities among the four phytohormones in regulating various secondary metabolic biosynthetic pathways and also provides suggestions for further research.

Development of fungal cell factories for the production of secondary metabolites:Linking genomics and metabolism

The genomic era has revolutionized research on secondary metabolites and bioinformatics methods have in recent years revived the antibiotic discovery process after decades with only few new active molecules being identified.New computational tools are driven by genomics and metabolomics analysis,and enables rapid identification of novel secondary metabolites.To translate this increased discovery rate into industrial exploitation,it is necessary to integrate secondary metabolite pathways in the metabolic engineering process.In this review,we will describe the novel advances in discovery of secondary metabolites produced by filamentous fungi,highlight the utilization of genome-scale metabolic models(GEMs)in the design of fungal cell factories for the production of secondary metabolites and review strategies for optimizing secondary metabolite production through the construction of high yielding platform cell factories.