Analyses of effects of α-cembratrien-diol on cell morphology and transcriptome of Valsa mali var. mali

Chemical structures, biosynthesis, bioactivities, and utilisation values for the diterpenes produced in tobacco trichomes

Cembranoids and labdanes are two important types of diterpenes in tobacco (Nicotiana genus) that are predominantly found in the leaf and flower glandular trichome secretions. This is the first systematic review of the biosynthesis, chemical structures, bioactivities, and utilisation values of cembranoid and labdane diterpenes in tobacco. A total of 131 natural cembranoid diterpenes have been reported in tobacco since 1962; these were summarised and classified according to their chemical structure characteristics as isopropyl cembranoids (1-88), seco-cembranoids (89-103), chain cembranoids (104-123), and polycyclic cembranoids (124-131). Forty natural labdane diterpenes reported since 1961 were also summarised and divided into epoxy side chain labdanes (132-150) and epoxy-free side chain labdanes (151-171). Tobacco cembranoid and labdane diterpenes are both formed via the methylerythritol 4-phosphate pathway and are synthesised from geranylgeranyl diphosphate. Their biosynthetic pathways and the four key enzymes (cembratrienol synthase, cytochrome P450 hydroxylase, copalyl diphosphate synthase, and Z-abienol cyclase) that affect their biosynthesis have been described in detail. A systematic summary of the bioactivity and utilisation values of the cembranoid and labdane diterpenes is also provided. The agricultural bioactivities associated with cembranoid and labdane diterpenes include antimicrobial and insecticidal activities as well as induced resistance, while the medical bioactivities include cytotoxic and neuroprotective activities. Further research into the cembranoid and labdane diterpenes will help to promote their development and utilisation as plant-derived pesticides and medicines.

Biosynthetic pathway redesign in non-conventional yeast for enhanced production of cembratriene-ol

Cembratriene-ol (CBT-ol), a plant-derived macrocyclic diterpene with notable insecticidal activity, has attracted considerable attention with respect to the development of sustainable and green biopesticides. Currently, CBT-ol production is limited by an inefficient and costly plant extraction strategy. Herein, CBT-ol production was enhanced by redesigning the CBT-ol biosynthetic pathway in Candida tropicalis, with subsequent truncation of CBT-ol synthase further increasing CBT-ol production. Moreover, bottlenecks in the CBT-ol biosynthetic pathway were eliminated by adjusting the gene dosage of the rate-limiting enzymes. Ultimately, the resulting strain C. tropicalis CPPt-03D produced 129.17 mg/L CBT-ol in shaking flasks (a 144-fold increase relative to that of the initial strain C01-CD) with CBT-ol production reaching 1,425.76 mg/L in a 5-L bioreactor, representing the highest CBT-ol titer reported to date. These findings provide a green process and promising platform for the industrial production of CBT-ol and lays the foundation for organic farming.

Natural products in crop protection: thiosemicarbazone derivatives of 3-acetyl-N-benzylindoles as antifungal agents and their mechanism of action

BACKGROUND

Phytopathogenic fungi can cause a direct loss in economic value of agriculture. Especially Valsa mali Miyabe et Yamada, a devastating phytopathogenic disease especially threatening global apple production, is very difficult to control and manage. To discover new potential antifungal agents, a series of thiosemicarbazone derivatives of 3-acetyl-N-benzylindoles were prepared. Their antifungal activities were first tested against six typically phytopathogenic fungi including Curvularia lunata, Valsa mali, Alternaria alternate, Fusarium graminearum, Botrytis cinerea and Fusarium solani. Then their mechanism of action against V. mali was investigated.

RESULTS

Derivatives displayed potent antifungal activity against V. mali. Notably, 3-acetyl-N-benzylindole thiosemicarbazone (IV-1: EC₅₀ : 0.59 μg mL^-1 ), whose activity was comparable to that of a commercial fungicide carbendazim (EC₅₀ : 0.33 μg mL^-1 ), showed greater than 98-fold antifungal activity of the precursor indole. Moreover, compound IV-1 displayed good protective and therapeutic effects on apple Valsa canker disease. By scanning electron microscope (SEM) and RNA-Seq analysis, it was demonstrated that compound IV-1 can destroy the hyphal structure and regulate the homeostasis of metabolism of V. mali via the ergosterol biosynthesis and autophagy pathways.

CONCLUSION

3-Acetyl-N-(un)substituted benzylindoles thiosemicarbazones (IV-1-IV-5) can be studied as leads for further structural modification as antifungal agents against V. mali. Particularly, these ergosterol biosynthesis and autophagy pathways can be used as target receptors for design of novel green pesticides for management of congeneric phytopathogenic fungi. © 2023 Society of Chemical Industry.

2E,4E-Decadienoic Acid, a Novel Anti-Oomycete Agent from Coculture of Bacillus subtilis and Trichoderma asperellum

Phytophthora nicotianae is an oomycete pathogen of global significance threatening many important crops. It is mainly controlled by chemosynthetic fungicides, which endangers ecosystem and human health; thus, there is an urgent need to explore alternatives for these fungicides. In this study, a new anti-oomycete aliphatic compound, 2E,4E-decadienoic acid (DDA), was obtained through coculture of Bacillus subtilis Tpb55 and Trichoderma asperellum HG1. Both in vitro and in vivo tests showed that DDA had a strong inhibitory effect against P. nicotianae. In addition, rhizosphere microbiome analysis showed that DDA reduced the relative abundance of Oomycota in rhizosphere soil. Transcriptome sequencing (RNA-Seq) analysis revealed that treatment of P. nicotianae with DDA resulted in significant downregulation of antioxidant activity and energy metabolism, including antioxidant enzymes and ATP generation, and upregulation of membrane-destabilizing activity, such as phospholipid synthesis and degradation. The metabolomic analysis results implied that the pathways influenced by DDA were mainly related to carbohydrate metabolism, energy metabolism, and the cell membrane. The biophysical tests further indicated that DDA produced oxidative stress on P. nicotianae, inhibited antioxidant enzyme and ATPase activity, and increased cell membrane permeability. Overall, DDA exerts inhibitory activity by acting on multiple targets in P. nicotianae, especially on the cell membrane and mitochondria, and can therefore serve as a novel environment-friendly agent for controlling crop oomycete disease. IMPORTANCE P. nicotianae is an oomycete pathogen that is destructive to crops. Although some oomycete inhibitors have been used during crop production, most are harmful to the ecology and lead to pathogen resistance. Alternatively, medium-chain fatty acids have been reported to exhibit antimicrobial activity in the medical field in previous studies; however, their potential as biocontrol agents has rarely been evaluated. Our in vivo and in vitro analyses revealed that the medium-chain fatty acid 2E,4E-decadienoic acid (DDA) displayed specific inhibitory activity against oomycetes. Further analysis indicated that DDA may acted on multiple targets in P. nicotianae, especially on the cell membrane and mitochondria. Our findings highlight the potential of DDA in controlling oomycete diseases. In conclusion, these results provide insights regarding the future use of green and environment-friendly anti-oomycete natural products for the prevention and control of crop oomycete diseases.

Structural Modifications and Biological Activities of Natural α- and β-Cembrenediol: A Comprehensive Review

As one of the most characteristic ingredients of glandular trichome secretions from Nicotiana tabacum L. (tobacco), natural cembrenediols, namely, (1S,2E,4S,6R,7E,11E)-2,7,11-cembratriene-4,6-diol (α-cembrenediol/α-CBD) and its C-4 epimer (β-cembrenediol/β-CBD), have attracted considerable attention for their potent antitumor, neuroprotective, antimicrobial, and other activities. Many researchers are committed to exploring the possibility of utilizing these two cembrenediols and their derivatives both in human medicine and in agricultural fungicides. To the best of our knowledge, this review is the first to provide a comprehensive summary of the chemical modifications and bioactivities of α- and β-CBD from their discovery to the present day; the review highlights their potential medicinal value for humans. The extensive references from 1962 to 2022 provided herein were systematically gathered from the SciFinder, Web of Science, and Google Scholar databases. We expect this review to assist in providing practical ideas for future drug development based on α- and β-CBD and in further facilitating the utilization of the tobacco cembrenediols.

Melatonin alleviates cadmium toxicity and abiotic stress by promoting glandular trichome development and antioxidant capacity in Nicotiana tabacum

Melatonin is a well-known signaling molecule that mediates a range of physiological activities and various stress reactions in plants. We comprehensively tested the effect of melatonin on the development of root hairs and glandular trichomes and found that melatonin pretreatment of tobacco seeds significantly increased the length of root hairs. Furthermore, melatonin-treated tobacco exhibited significantly higher density of trichomes and larger glandular heads on long-stalk glandular trichomes than untreated plants, which resulted in enhanced secretion in glandular trichomes. Exogenous melatonin enhanced the aphid resistance of plants by facilitating the accumulation of cembranoids in the glandular trichomes and alleviated cadmium toxicity by increasing the Cd-exudation capacity of long glandular trichomes. Metabolic analysis indicated that the contents of 108 metabolites significantly changed upon melatonin treatment, with the contents of those that are directly/indirectly involved in melatonin metabolism changing the most. Further, KEGG pathway analysis suggested that the metabolic pathways of amino acids, reducing sugar, secondary metabolites, indole alkaloid biosynthesis, purine, pyrimidine, and ABC transporters were greatly influenced by exogenous melatonin application. Moreover, metabolisms of melatonin-related antioxidants and pyrimidine nucleoside antibiotics were enhanced after melatonin treatment. Melatonin improved tobacco resistance to high salinity, drought, and extreme temperature stresses, as indicated by improved photosynthetic and antioxidant capacities in treated vs. untreated plants. This study lays a foundation for the comprehensive application of melatonin to increase the stress tolerance of plants.

The Tobacco β-Cembrenediol: A Prostate Cancer Recurrence Suppressor Lead and Prospective Scaffold via Modulation of Indoleamine 2,3-Dioxygenase and Tryptophan Dioxygenase

Prostate cancer (PC) is the second leading cause of death in men in the US. PC has a high recurrence rate, and limited therapeutic options are available to prevent disease recurrence. The tryptophan-degrading enzymes 2,3-indoleamine dioxygenase (IDO1) and tryptophan dioxygenase (TDO2) are upregulated in invasive PC. (1S,2E,4R,6R,7E,11E)-2,7,11-cembratriene-4,6-diol (β-CBT) and its C-4 epimer α-CBT are the precursors to key flavor ingredients in tobacco leaves. Nearly 40-60% of β- and α-CBT are purposely degraded during commercial tobacco fermentation. Earlier, β-CBT inhibited invasion, reversed calcitonin-stimulated transepithelial resistance decrease, and induced tighter intercellular barriers in PC-3M cells. This study demonstrates the in vitro β-CBT anti-migratory (wound-healing assay) and anti-clonogenicity (colony-formation assay) activities against five diverse human PC cell lines, including the androgen-independent PC-3, PC-3M, and DU-145, the castration-recurrent CWR-R1ca, and the androgen-dependent CWR-22rv1. Meanwhile, β-CBT potently suppressed in vivo locoregional and distant recurrences after the primary tumor surgical excision of PC-3M-Luc cell tumor engrafted in male nude mice. β-CBT treatments suppressed organ and bone metastasis and lacked any major toxicity over the 60-day study course. β-CBT treatments significantly suppressed IDO1, TDO2, and their final metabolite kynurenine levels in PC-3M cells. β-CBT treatments significantly suppressed the tumor recurrence marker PSA and kynurenine levels in treated animals' plasma. β-CBT emerges as a promising PC recurrence suppressive lead.

Chemical Constituents from Nicotiana tabacum L. and Their Antifungal Activity

A phytochemical investigation of an aqueous ethyl alcohol (EtOH) extract of the flowers of Nicotiana tabacum L . led to the identification of one new eudesmane-type sesquiterpenoid (1) and 14 known compounds, including 7 flavones (2-8), 6 phenolic acids (9-14), and 1 coumarin (15). The chemical structure of 1 was established on the basis of high-resolution electrospray ionization (HRESIMS) and 1D and 2D NMR analyses, while the other structures were elucidated by 1D NMR and LC–MS data. The antiphytopathogenic activities of all the isolated compounds were tested to determine their antifungal activity against Valsa mali var. mali, Alternaria porri, and Botrytis cinerea at a concentration of 10 µg/mL. Compound 4 exhibited more potent antifungal effects against Valsa mali var. mali with a % growth inhibition of 47.9 ± 1.2%, while the others only showed insignificant activities.

Compositional analysis of bio-oils from hydrothermal liquefaction of tobacco residues using two-dimensional gas chromatography and time-of-flight mass spectrometry

Sustainable energy from biomass is one of the most promising alternative energy sources and is expected to partially replace fossil fuels. Tobacco industries have normally rid their processing residues by landfilling or incineration, affecting the environment negatively. These residues can be used to either extract high-value chemicals or generate bio-energy via hydrothermal liquefaction. The main liquid product or bio-oil consists of highly complicated chemicals. In this work, the bio-oil from hydrothermal liquefaction of tobacco processing residues was generated in a batch reactor at biomass-to-deionized water ratio of 1:3, temperature of 310°C, and 15 min residence time, yielding the maximum liquid products for more than 50% w/w. The liquid products were analyzed, using two-dimensional gas chromatography and time-of-flight mass spectrometry (GC × GC/TOF MS). This technique allowed for a highly efficient detection of numerous compounds. From the results, it was found that hydrothermal liquefaction can cleave biopolymers (cellulose, hemicellulose, and lignin) in tobacco residues successfully. The hydrothermal liquefaction liquid products can be separated into heavy organic, light organic, and aqueous phase fractions. By GC × GC/TOF MS, the biopolymers disintegrated into low molecular weight compounds and classified by their chemical derivatives and functional groups could be detected. The major chemical derivative/functional groups found were cyclic ketones and phenols for heavy organic and light organic, and carboxylic acids and N-containing compounds for the aqueous phase. Additionally, by the major compounds found in this work, simple pathway reactions occurring in the hydrothermal liquefaction reaction were proposed, leading to a better understanding of the hydrothermal liquefaction process for tobacco residues.

iTRAQ-based proteomic analysis reveals the molecule mechanism of reducing higher alcohols in Chinese rice wine by nitrogen compensation

Purpose

Higher alcohol is a by-product of the fermentation of wine, and its content is one of the most important parameters that affect and are used to appraise the final quality of Chinese rice wine. Ammonium compensation is an efficient and convenient method to reduce the content of higher alcohols, but the molecule mechanism is poorly understood. Therefore, an iTRAQ-based proteomic analysis was designed to reveal the proteomic changes of Saccharomyces cerevisiae to elucidate the molecular mechanism of ammonium compensation in reducing the content of higher alcohols.

Methods

The iTRAQ proteomic analysis method was used to analyze a blank group and an experimental group with an exogenous addition of 200 mg/L (NH4)2HPO4 during inoculation. The extracted intracellular proteins were processed by liquid chromatography-mass spectrometry and identified using bioinformatics tools. Real-time quantitative polymerase chain reaction was used to verify the gene expression of differentially expressed proteins.

Results

About 4062 proteins, including 123 upregulated and 88 downregulated proteins, were identified by iTRAQ-based proteomic analysis. GO and KEGG analysis uncovered that significant proteins were concentrated during carbohydrate metabolism, such as carbon metabolism, glyoxylate, and dicarboxylate metabolism, pyruvate metabolism, and the nitrogen metabolism, such as amino acid synthesis and catabolism pathway. In accordance with the trend of differential protein regulation in the central carbon metabolism pathway and the analysis of carbon metabolic flux, a possible regulatory model was proposed and verified, in which ammonium compensation facilitated glucose consumption, regulated metabolic flow direction into tricarboxylic acid, and further led to a decrease in higher alcohols. The results of RT-qPCR confirmed the authenticity of the proteomic analysis results at the level of gene.

Conclusion

Ammonium assimilation promoted by ammonium compensation regulated the intracellular carbon metabolism of S. cerevisiae and affected the distribution of metabolic flux. The carbon flow that should have gone to the synthesis pathway of higher alcohols was reversed to the TCA cycle, thereby decreasing the content of higher alcohols. These findings may contribute to an improved understanding of the molecular mechanism for the decrease in higher alcohol content through ammonium compensation.

Antifungal activity of chitosan against Aspergillus ochraceus and its possible mechanisms of action

Chitosan is a polysaccharide with a wide-range antimicrobial spectrum and has been shown to be effective in control postharvest diseases of various fruit, but the possible mode of action is far from well known. In this study the antifungal activity of chitosan was tested on A. ochraceus and its possible mechanisms involved were also investigated both at microstructure and transcriptome level. Here, we found that chitosan could significantly inhibited spore germination and mycelia growth of A. ochraceus. Scan electron microscopy (SEM) and transmission electron microscopy (TEM) observations showed that chitosan induced remarkable changes in morphology and microstructure of hyphae, such as shriveling, abnormal branching and vacuolation. Changes in expression profiles of A. ochraceus upon chitosan treatment were analyzed by RNA sequencing and a total of 435 differentially expressed genes (DEGs) were identified. Further KEGG analysis revealed that DEGs involved in ribosome biogenesis were down-regulated, while DEGs related to membrane homeostasis, such as glycerophospholipid metabolism, ether lipid metabolism and steroid biosynthesis, were up-regulated. Chitosan may affect the growth and development of A. ochraceus by impairing the integrity of cell surface architecture and protein biosynthesis. These findings have practical implications with respect to the use of chitosan as an alternative way for controlling fungal pathogens.

Dynamics of antioxidant activities, metabolites, phenolic acids, flavonoids, and phenolic biosynthetic genes in germinating Chinese wild rice (Zizania latifolia)

In this study, the antioxidant activity of germinating Chinese wild rice was found to decline initially, after which it increased. The largest difference in antioxidant activity was observed between the 36-h (G36) and the 120-h germination (G120) stage. We further assessed the dynamic changes in metabolites, phenolic acids, flavonoids, and phenolic biosynthetic genes in germinating Chinese wild rice. Ultra-high performance liquid chromatography-triple quadrupole mass spectrometry revealed that 315 metabolites were up-regulated and 28 were down-regulated between G36 and G120. Levels of p-hydroxybenzoic acid, p-hydroxybenzaldehyde, vanillin, p-coumaric acid, ferulic acid, and epigallocatechin increased significantly during germination. Gene expression of four phenylalanine ammonia-lyases, one 4-coumarate-CoA ligase, one cinnamoyl-CoA reductase, two cinnamyl alcohol dehydrogenases, one chalcone synthase, and one chalcone isomerase was significantly higher at G120 than at G36 and promoted phenolics accumulation. This study elucidated the biochemical mechanisms involved in antioxidant activity and phenolic profile changes during Chinese wild rice germination.

Microwave-assisted hydrothermal extraction of non-structural carbohydrates and hemicelluloses from tobacco biomass

Microwave-assisted hydrothermal extraction of non-structural carbohydrates and hemicelluloses from tobacco biomass was investigated. Non-structural carbohydrates extraction was optimized by an Optimal design. The maximum yields for the leaf and stem were 118.57 mg/g and 120.33 mg/g biomass, respectively. The extracted stem residue was further treated for hemicelluloses extraction. A temperature of 200 °C without holding was proved to be the most efficient condition to produce a hemicelluloses yield of 105.15 mg/g. GPC results showed that the Mw values of precipitated hemicelluloses decreased from 143.5 kDa to 13.25 kDa with increasing temperature and holding time, while the un-precipitated fraction were ranging from 11.83 to 4.88 kDa. Monosaccharide analysis revealed that hemicelluloses extracted at lower temperature are heterogeneous compositional type, including xylan, glucuronoxylan and xylanglucan, while the ratio of xylose increased significantly (up to 72.64%) with increasing temperature. The developed microwave-assisted hydrothermal extraction process opens new avenues for a sustainable tobacco-based biorefinery.

Genome-wide characterization of NtHD-ZIP IV: different roles in abiotic stress response and glandular Trichome induction

BACKGROUND

The plant-specific homeodomain-leucine zipper class IV (HD-ZIP IV) gene family has been involved in the regulation of epidermal development.

RESULTS

Fifteen genes coding for HD-ZIP IV proteins were identified (NtHD-ZIP-IV-1 to NtHD-ZIP-IV-15) based on the genome of N. tabacum. Four major domains (HD, ZIP, SAD and START) were present in these proteins. Tissue expression pattern analysis indicated that NtHD-ZIP-IV-1, - 2, - 3, - 10, and - 12 may be associated with trichome development; NtHD-ZIP-IV-8 was expressed only in cotyledons; NtHD-ZIP-IV-9 only in the leaf and stem epidermis; NtHD-ZIP-IV-11 only in leaves; and NtHD-ZIP-IV-15 only in the root and stem epidermis. We found that jasmonates may induce the generation of glandular trichomes, and that NtHD-ZIP-IV-1, - 2, - 5, and - 7 were response to MeJA treatment. Dynamic expression under abiotic stress and after application of phytohormones indicated that most NtHD-ZIP IV genes were induced by heat, cold, salt and drought. Furthermore, most of these genes were induced by gibberellic acid, 6-benzylaminopurine, and salicylic acid, but were inhibited by abscisic acid. NtHD-ZIP IV genes were sensitive to heat, but insensitive to osmotic stress.

CONCLUSION

NtHD-ZIP IV genes are implicated in a complex regulatory gene network controlling epidermal development and abiotic stress responses. The present study provides evidence to elucidate the gene functions of NtHD-ZIP IVs during epidermal development and stress response.

Bioactivities and Medicinal Value of Solanesol and Its Accumulation, Extraction Technology, and Determination Methods

Solanesol, an aliphatic terpene alcohol composed of nine isoprene units, is mainly found in solanaceous plants. Particularly, tobacco (Nicotiana tabacum), belonging to the Solanaceae family, is the richest plant source of solanesol, and its leaves have been regarded as the ideal material for solanesol extraction. Since the discovery of solanesol in tobacco, significant progress has been achieved in research on solanesol’s bioactivities, medicinal value, accumulation, extraction technology, and determination methods. Solanesol possesses strong free radical absorption ability and antioxidant activity owing to the presence of several non-conjugated double bonds. Notably, solanesol’s anti-inflammatory, neuroprotective, and antimicrobial activities have been previously demonstrated. Solanesol is a key intermediate in the synthesis of coenzyme Q10, vitamin K2, and the anticancer agent synergiser N-solanesyl-N,N′-bis(3,4-dimethoxybenzyl) ethylenediamine. Other applications of solanesol include solanesol derivative micelles for hydrophobic drug delivery, solanesol-derived scaffolds for bioactive peptide multimerization, and solanesol-anchored DNA for mediating vesicle fusion. Solanesol accumulation in plants is influenced by genetic and environmental factors, including biotic stresses caused by pathogen infections, temperature, illumination, and agronomic measures. Seven extraction technologies and seven determination methods of solanesol are also systematically summarized in the present review. This review can serve as a reference for solanesol’s comprehensive application.

iTRAQ-based proteomic analysis reveals the accumulation of bioactive compounds in Chinese wild rice (Zizania latifolia) during germination

Polyphenols and γ-aminobutyric acid (GABA) accumulate during seed germination, but the mechanisms involved are poorly understood. The objective of this study was to elucidate the accumulation of these bioactive compounds in Chinese wild rice during germination. The greatest differences in the phenolic content were at 36-h (G36) and 120-h germination (G120) stages. An iTRAQ-based proteomic analysis revealed 7031 proteins, and a comparison of the G120 and G36 stages revealed 956 upregulated and 188 downregulated proteins. The KEGG analysis revealed significant protein enrichment in the "metabolic pathways", "biosynthesis of secondary metabolites" and "phenylpropanoid biosynthesis". Four phenylalanine ammonia-lyases, one 4-coumarate-CoA ligase, one cinnamoyl-CoA reductase, two cinnamyl alcohol dehydrogenases, and four glutamate decarboxylases exhibited higher expression at the G120 than at the G36 stage and promoted phenolics and GABA accumulation. This study revealed bioactive compound accumulation in germinating Chinese wild rice, and the finding may help develop functional foods derived from this cereal.

A Review on Bioactivities of Tobacco Cembranoid Diterpenes

Cembranoids are carbocyclic diterpenes comprising four isoprene units and are natural products with a parent skeleton consisting of a 14-membered ring. They have gained wide interest in recent years and are a major hotspot in the research of natural product chemistry. Since 1962, various tobacco cembranoid diterpenes have been identified. This review systematically discusses and summarises the excellent antimicrobial, insecticidal, cytotoxic and neuroprotective activities of tobacco cembranoid diterpenes. These compounds show potential to be developed as botanical fungicides, cytotoxic drugs and drugs for the treatment of human immunodeficiency virus, Alzheimer's disease, Parkinson's disease, and other neurodegenerative diseases. However, there are relatively few studies on the structure⁻activity relationship (SAR) of tobacco cembranoid diterpenes. Therefore, future studies should focus on their structural modification, SAR and biogenic relationships.

RNA Sequencing Provides Insights into the Regulation of Solanesol Biosynthesis in Nicotiana tabacum Induced by Moderately High Temperature

Solanesol is a terpene alcohol composed of nine isoprene units that mainly accumulates in solanaceous plants, especially tobacco (Nicotiana tabacum). The present study aimed to investigate the regulation of solanesol accumulation in tobacco leaves induced by moderately high temperature (MHT). Exposure to MHT resulted in a significant increase in solanesol content, dry weight, and net photosynthetic rate in tobacco leaves. In MHT-exposed tobacco leaves, 492 and 1440 genes were significantly up- and downregulated, respectively, as revealed by RNA-sequencing. Functional enrichment analysis revealed that most of the differentially expressed genes (DEGs) were mainly related to secondary metabolite biosynthesis, metabolic pathway, carbohydrate metabolism, lipid metabolism, hydrolase activity, catalytic activity, and oxidation-reduction process. Moreover, 122 transcription factors of DEGs were divided into 22 families. Significant upregulation of N. tabacum 3-hydroxy-3-methylglutaryl-CoA reductase (NtHMGR), 1-deoxy-d-xylulose 5-phosphate reductoisomerase (NtDXR), geranylgeranyl diphosphate synthase (NtGGPS), and solanesyl diphosphate synthase (NtSPS) and significant downregulation of N. tabacum 1-deoxy-d-xylulose 5-phosphate synthase (NtDXS) and farnesyl diphosphate synthase (NtFPS) transcription upon MHT exposure were monitored by quantitative real-time PCR (qRT-PCR). This study indicated that solanesol accumulation in tobacco leaves can be manipulated through regulation of the environmental temperature and established a basis for further elucidation of the molecular mechanism of temperature regulation of solanesol accumulation.

Transcriptomic response of Ralstonia solanacearum to antimicrobial Pseudomonas fluorescens SN15-2 metabolites

To develop efficient biocontrol agents, it is essential to investigate the response of soil-borne plant pathogens to such agents. For example, the response of Ralstonia solanacearum, the tomato wilt pathogen, to antimicrobial metabolites of Pseudomonas fluorescens is unknown. Thus, we assessed the effects of P. fluorescens SN15-2 fermentation broth on R. solanacearum by transmission electron microscopy and transcriptome technology. RNA sequencing identified 109 and 155 genes that are significantly upregulated and downregulated, respectively, in response to P. fluorescens metabolites, many of which are associated with the cell membrane and cell wall, and with nucleotide acid metabolism, iron absorption, and response to oxidative stress. This study highlights the effectiveness of P. fluorescens metabolites against the tomato wilt pathogen and helps clarify the underlying molecular mechanisms.

Metabolic Flux Engineering of Cembratrien-ol Production in Both the Glandular Trichome and Leaf Mesophyll in Nicotiana tabacum

Cembratrien-ol synthase (CBTS) catalyzes the first step in cembranoid biosynthesis, producing cembratrien-ols in plant trichomes. In our previous study, microarray transcriptomes between leaves with trichomes and leaves without trichomes showed that an NtCBTS2 gene was expressed exclusively and abundantly in trichomes. Here, two NtCBTS2 isogenes (NtCBTS2a and NtCBTS2b), derived from a diploid genome donor, Nicotiana sylvestris, were identified from N. tabacum. Both genes were expressed primarily in trichomes, with relatively decreased transcription in flowers and stems, and faint expression in roots, and no expression was detected in leaves lacking trichomes. To demonstrate the feasibility of producing natural product cembratrien-ols in tobacco mesophylls, the mesophylls of 35S:NtCBTS2b transgenic tobacco plants were used in the analysis, suggesting that constitutive expression of NtCBTS2b led to the cembratrien-ol production in mesophylls. Overexpression of NtCBTS2b using either Cauliflower mosaic virus (CaMV) 35S or trichome-specific Cyt P450 oxygenase (CYP) promoters greatly increased aphid resistance by promoting the accumulation of CBT-ols, increased the secretory cell growth in glandular trichomes and increased the levels of various physiological measures, including sugar esters, gibberellins, and cembranoid production. Meanwhile, specifically overexpressing NtCBTS2b in glandular trichomes could most efficiently promote aphid resistance in tobacco plants. Notably, our results indicate the feasibility of utilizing bio-engineering to produce large amounts of CBT-ols, and modify significantly the composition of naturally produced CBT-ols and CBT-diols, thereby promoting aphid resistance in plants.

Genome-Wide Analysis of Long Non-Coding RNAs in Potato and Their Potential Role in Tuber Sprouting Process

Sprouting is a key factor affecting the quality of potato tubers. The present study aimed to compare the differential expression of long non-coding RNAs (lncRNAs) in the apical meristem during the dormancy release and sprouting stages by using lncRNA sequencing. Microscopic observations and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed the changes in the morphology and expression of lncRNAs in potato tubers during sprouting. Meristematic cells of potato tuber apical buds divided continuously and exhibited vegetative cone bulging and vascularisation. In all, 3175 lncRNAs were identified from the apical buds of potato tubers, among which 383 lncRNAs were up-regulated and 340 were down-regulated during sprouting. The GO enrichment analysis revealed that sprouting mainly influenced the expression of lncRNAs related to the cellular components of potato apical buds (e.g., cytoplasm and organelles) and cellular metabolic processes. The KEGG enrichment analysis also showed significant enrichment of specific metabolic pathways. In addition, 386 differentially expressed lncRNAs during sprouting were identified as putative targets of 235 potato miRNAs. Quantitative real-time polymerase chain reaction results agreed with the sequencing data. Our study provides the first systematic study of numerous lncRNAs involved in the potato tuber sprouting process and lays the foundation for further studies to elucidate their precise functions.

The tobacco cembranoid (1S,2E,4S,7E,11E)-2,7,11-cembratriene-4,6-diol as a novel angiogenesis inhibitory lead for the control of breast malignancies

(1S,2E,4S,6R,7E,11E)-2,7,11-cembratriene-4,6-diol (1) and its 4-epi-analog (2) are diterpene precursors of the key flavor components in most Nicotiana (tobacco) species that purposely degraded during commercial tobacco fermentation. Angiogenesis, recruitment of new blood vessels, is important for tumor growth, survival and metastasis that can be targeted to control cancer. This study shows evidences and potential of the cembranoid 1 as a potent angiogenesis modulator through targeting VEGFR2. In silico study suggested favorable docking scores and binding affinity of 1 at the ATP binding pocket of VEGFR2. The binding mode of 1 was parallel to the standard FDA-approved antiangiogenic drug sunitinib (4). In vitro, cembranoid 1 significantly reduced the activated VEGFR2 levels in multiple breast cancer cell lines. Intraperitoneal 40mg/kg, 3X/week treatment of 1 significantly reduced the MDA-MB-231 cells breast tumor size in mice. Immunohistochemistry and Western blotting analysis of the treated mice tumors showed significant downregulation of the vasculogenesis marker CD31 and suppressed activated VEGFR2-paxillin-FAK pathway. Matrigel study in Swiss albino mice showed similar trend. The tobacco cembranoid 1 is a potential antiangiogenic lead useful for future use to control breast malignancies.

Chemical Basis of the Fungicidal Activity of Tobacco Extracts against Valsa mali

Under pressure from social criticism and an unclear future, tobacco researchers have begun to seek alternative uses for the product. Here, we present our study on isolating tobacco compounds with fungicidal activity, which could be used as plant-derived pesticides. Using Valsa mali as the target fungus, agar plate tests were conducted to evaluate the fungicidal activity of various tobacco extracts, including tobacco leaves extracts prepared with different solvents, extracts of different tobacco cultivars, and samples from different tobacco organs. Fungal growth morphology was used as the criterion to evaluate the fungicidal activity of tobacco extracts. Correlation analyses between the fungicidal activities and the chemical components of tobacco extracts indicated the major chemical constituents with fungicidal activity. Then, the active compounds were isolated and their effects on the ultra-microstructures of V. mali was analyzed using scanning- and transmission-electron microscopy. The results suggested that tobacco extracts prepared with solvents of weaker polarity had higher fungicidal activity, and the inhibitory activity of tobacco extracts against V. mali was also cultivar dependent. Furthermore, the fungicidal effects of tobacco flower extracts were higher than those of the leaf extracts. Chemical analysis indicated that cembranoids were the main fungicidal substances, which act by destroying the endometrial structure of the fungus. Tobacco cembranoids at 80 μg/mL could completely inhibit the growth of V.mali, with an EC50 value of 13.18 μg/mL. Our study therefore suggests that tobacco leaves and inflorescences are excellent plant resources for the biological control of V. mali.