Peltate Glandular Trichomes Research Articles

Morphology of glandular trichomes of Japanese catnip (Schizonepeta tenuifolia Briquet) and developmental dynamics of their secretory activity

Schizonepeta tenuifolia Briquet, commonly known as Japanese catnip, is used for the treatment of colds, headaches, fevers, and skin rashes in traditional Asian medicine (China, Japan and Korea). The volatile oil and its constituents have various demonstrated biological activities, but there is currently limited information regarding the site of biosynthesis. Light microscopy and scanning electron microscopy indicated the presence of three distinct glandular trichome types which, based on their morphological features, are referred to as peltate, capitate and digitiform glandular trichomes. Laser scanning microscopy and 3D reconstruction demonstrated that terpenoid-producing peltate glandular trichomes contain a disk of twelve secretory cells. The oil of peltate glandular trichomes, collected by laser microdissection or using custom-made micropipettes, was demonstrated to contain (−)-pulegone, (+)-menthone and (+)-limonene as major constituents. Digitiform and capitate glandular trichomes did not contain appreciable levels of terpenoid volatiles. The yield of distilled oil from spikes was significantly (44%) higher than that from leaves, while the composition of oils was very similar. Oils collected directly from leaf peltate glandular trichomes over the course of a growing season contained primarily (−)-pulegone (>80% at 32 days after germination) in young plants, while (+)-menthone began to accumulate later (>75% at 80 days after germination), at the expense of (−)-pulegone (the levels of (+)-limonene remained fairly stable at 3–5%). The current study establishes the morphological and chemical characteristics of glandular trichome types of S. tenuifolia, and also provides the basis for unraveling the biosynthesis of essential oil in this popular medicinal plant.

Ergot Alkaloids and their Hallucinogenic Potential in Morning Glories.

Naturally occurring and semisynthetic ergot alkaloids play a role in health care or as recreational drugs in Western and indigenous Mexican societies. Evidence is summarized that ergot alkaloids present in Central American Convolvulaceae like Turbina corymbosa, Ipomoea violacea, and Ipomoea asarifolia are colonized by different species of a newly described clavicipitaceous fungal genus named Periglandula. The fungi are associated with peltate glandular trichomes on the adaxial leaf surface of its host plants. The Periglandula fungi are not yet culturable in vitro but were demonstrated to have the capacity to synthesize ergot alkaloids. The alkaloids do not remain in the fungal mycelium but are translocated via the glandular trichomes into their plant host. Both fungi and host benefit from a symbiotic lifestyle. In evolutionary terms the alkaloid biosynthetic gene cluster in the Periglandula/Ipomoea symbiosis is likely to have a conserved (basic) structure while biosynthetic ergot gene clusters within the genera Claviceps and Epichloe were under ecological selection for alkaloid diversification.

Chemical Composition and Biological Activities of The Essential Oil And Anatomical Markers Of Lavandula Dentata L. Cultivated In Brazil

ABSTRACT Lavandula dentata, popularly known as lavender, is commonly used in traditional medicine for the treatment of digestive and inflammatory disorders. The objective of this study was to analyzed the chemical oil composition, antioxidant and antimicrobial activities of the essential oil and anatomical markers of the leaf and stem of L. dentata cultivated in South Brazil. Essential oil showed an antioxidant activity similar to rutin and gallic acid when analyzed by phosphomolybdenum method. However, by the free radical DPPH and ABTS methods, it showed a slight potential antioxidant. Essential oil presented 1,8-cineol (63%) as major component, antimicrobial activity against Gram-positive, Gram-negative bacteria strains and Candida albicans, by broth microdilution. The anatomical profile provided the following main microscopic markers: hypostomatic leaves; diacytic stomata, thin and striate cuticle; multicellular and branched non-glandular trichomes; capitate glandular trichomes; peltate glandular trichomes; dorsiventral mesophyll; flat-convex shape midrib, truncated on the abaxial side; one collateral vascular bundle in the midrib; square stem shape, angular collenchyma alternated with cortical parenchyma; sclerenchymatic fibers well-developed on the four edges.

Influence of growth regulators on distribution of trichomes and the production of volatiles in micropropagated plants of Plectranthus ornatus

The profile of volatile organic compounds, the glandular and non-glandular trichomes of Plectranthus ornatus, obtained by in vitro cultivation, was evaluated in plants grown in Murashide and Skoog medium supplemented with benylaminopurine at 4.5, 9.0, and 18.0μM+naphthaleneacetic acid at 5.37μM, kinetin at 4.7, 9.3 and 18.5μM+naphthaleneacetic acid (5.37μM) or Murashide and Skoog 0 medium (as a control). Scanning Electron Microscopy was performed on samples of the third leaf node of the 90 days old plants obtained from treatment with 4.5 or 9.0μM benylaminopurine, and 4.7 or 9.3μM kinetin. Headspace Solid Phase Micro-Extraction of the 30, 60 and 90 days old in vitro plants permitted to determinate by GC/MS the composition comprised of 62 compounds. The data were analyzed using Principal Component Analysis and Hierarchical Clustering Analysis and, the major constituents of these oils after treatment and aging were monoterpenes and sesquiterpenes. Morphoanatomical analysis of trichomes, by Scanning Electron Microscopy, enabled the identification of non-glandular trichomes and four types of glandular trichomes, which comprised capitate and peltate glandular trichomes that were distributed on both sides of the leaf. We observed that the regulators influenced qualitative and quantitative profiles of the volatile organic compounds and the number and distribution of hairs on the leaf surface.

Structural re-arrangement of depolymerized sodium alginate enriches peltate glandular trichomes and essential oil production of spearmint

Over the past decade, radiation-degraded polysaccharides have been used as regulators of growth and development in several crop plants. In quest of the possible reasons of previously established growth-promotion activity of irradiated sodium alginate (ISA), structural parameters of irradiated and un-irradiated sodium alginate were analysed using Ultraviolet-visible spectroscopy (UV–vis) and Fourier Transform Infrared spectroscopic (FT–IR) studies to develop an understanding of structure-property relationship. Using foliar application, response to graded concentrations of ISA was tested in terms of yield and quality attributes of spearmint (Mentha spicata L.). Among different concentrations of ISA [0 (control), 40, 80, 120 and 160mgL−1], 80mgL−1 proved to be the optimum foliar-spray treatment for most of the parameters studied including peltate glandular-trichomes density, which was increased from 20 to 44mm−2. Measurements made at 150days after planting revealed that foliar application of ISA at 80mgL−1 increased the content and yield of spearmint essential oil (EO) by 36.0 and 122.6%, respectively, in comparison to the control. Compared to the control, gas chromatography mass spectrometry (GC–MS) analysis revealed an increase of 18.7% in the carvone content and a decrease of 15.7% in limonene content of the spearmint EO.

Localisation of Two Bioactive Labdane Diterpenoids in the Peltate Glandular Trichomes of Leonurus japonicus by Laser Microdissection Coupled with UPLC-MS/MS.

Glandular trichomes of plants are biochemical factories that could produce, store and secrete copious pharmaceutically important natural products. The Labiatae plant Leonurus japonicus is an important traditional Chinese medicine used to treat gynecological diseases, and has abundant peltate glandular trichomes (PGTs), in which the secondary metabolites accumulated are still unknown. To study the secondary metabolites specifically accumulated in the PGTs of L. japonicus and their biological activities, and provide a new way to pinpoint bioactive natural products from plants. Morphology of the trichomes on L. japonicus were observed under a scanning electron microscope. The PGTs of L. japonicus were precisely collected using laser microdissection (LMD) and analysed for their secondary metabolites with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Targeted compounds were isolated with classical phytochemical methods, and their structures were elucidated by spectroscopic analysis. Biological activities were evaluated by in vitro assays. Two labdane diterpenoids, leoheterin (1) and galeopsin (2), were localised in the PGTs of L. japonicus. Antithrombotic activity of 1 in anti-platelet aggregation assay induced by arachidonic acid was observed. Both compounds showed potential anti-inflammatory activity by inhibiting proinflammatory cytokine TNF-α. In addition, anti-proliferative effect of both compounds on several cancer cell lines was also detected. Two bioactive labdane diterpenoids were localised in the PGTs of L. japonicus. The findings suggested that it might be an efficient approach to explore bioactive natural products from the glandular trichomes of medicinal plants with LMD-UPLC/MS/MS. Copyright © 2017 John Wiley & Sons, Ltd.

Spearmint R2R3-MYB transcription factor MsMYB negatively regulates monoterpene production and suppresses the expression of geranyl diphosphate synthase large subunit (MsGPPS.LSU).

SummaryMany aromatic plants, such as spearmint, produce valuable essential oils in specialized structures called peltate glandular trichomes (PGTs). Understanding the regulatory mechanisms behind the production of these important secondary metabolites will help design new approaches to engineer them. Here, we identified a PGT‐specific R2R3‐MYB gene, MsMYB, from comparative RNA‐Seq data of spearmint and functionally characterized it. Analysis of MsMYB‐RNAi transgenic lines showed increased levels of monoterpenes, and MsMYB‐overexpressing lines exhibited decreased levels of monoterpenes. These results suggest that MsMYB is a novel negative regulator of monoterpene biosynthesis. Ectopic expression of MsMYB, in sweet basil and tobacco, perturbed sesquiterpene‐ and diterpene‐derived metabolite production. In addition, we found that MsMYB binds to cis‐elements of MsGPPS.LSU and suppresses its expression. Phylogenetic analysis placed MsMYB in subgroup 7 of R2R3‐MYBs whose members govern phenylpropanoid pathway and are regulated by miR858. Analysis of transgenic lines showed that MsMYB is more specific to terpene biosynthesis as it did not affect metabolites derived from phenylpropanoid pathway. Further, our results indicate that MsMYB is probably not regulated by miR858, like other members of subgroup 7.

A (–)-kolavenyl diphosphate synthase catalyzes the first step of salvinorin A biosynthesis in Salvia divinorum

Salvia divinorum (Lamiaceae) is an annual herb used by indigenous cultures of Mexico for medicinal and ritual purposes. The biosynthesis of salvinorin A, its major bioactive neo-clerodane diterpenoid, remains virtually unknown. This investigation aimed to identify the enzyme that catalyzes the first reaction of salvinorin A biosynthesis, the formation of (-)-kolavenyl diphosphate [(-)-KPP], which is subsequently dephosphorylated to afford (-)-kolavenol. Peltate glandular trichomes were identified as the major and perhaps exclusive site of salvinorin accumulation in S. divinorum. The trichome-specific transcriptome was used to identify candidate diterpene synthases (diTPSs). In vitro and in planta characterization of a class II diTPS designated as SdKPS confirmed its activity as (-)-KPP synthase and its involvement in salvinorin A biosynthesis. Mutation of a phenylalanine into histidine in the active site of SdKPS completely converts the product from (-)-KPP into ent-copalyl diphosphate. Structural elements were identified that mediate the natural formation of the neo-clerodane backbone by this enzyme and suggest how SdKPS and other diTPSs may have evolved from ent-copalyl diphosphate synthase.

Effects of Plant Density on the Number of Glandular Trichomes and on Yield and Quality of Essential Oils from Oregano

Plants yields are influenced by agronomic techniques. Plant density is a complex issue and extremely important when maximizing both crop quality, and biomass and essential oil yields. Plants belonging to the Origanum vulgare subspecies hirtum (Link) Ietswaart were grown adopting four types of plant density and were characterized in biometric and chemical terms. The samples were analyzed using the ANOVA (Principal Component Analysis) statistical method regarding biometric aspects, EO yield and peltate hair density. Essential oil (EO) was extracted by hydrodistillation and analyzed using GC-FID and GC-MS. GC-FID and GC-MS analysis led to the identification of 45 compounds from the EO. Plant density affected production both in terms of biomass and EO. However, it was not found to have affected peltate glandular trichome density or EO quality.

Comparative micromorphology and anatomy of flowers and floral secretory structures in two Viburnum species

In entomogamous plants, the presence and function of floral secretory structures, whose main role is to attract pollinators, is strictly associated with the pollination ecology and hence the reproductive success of the plant. The aims of the present paper were to analyse the micromorphology and anatomy of flower nectaries and stigmas in Viburnum opulus and V. lantana and to determine the function and microstructure of inflorescence trichomes in both taxa using light and scanning electron microscopy as well as histochemical assays. It was found that stigmas were formed by papillae, which contained lipids, polysaccharides, tannins, and pigments. Stigmatic secretion proceeded via cuticular pores. Floral nectaries formed a thick layer around the styles, and nectar was secreted through numerous nectarostomata. There were no traces of vascular bundles penetrating the nectary tissue. In turn, numerous tannin deposits were observed in the cells of the glandular parenchyma. Pedicels, hypanthia, and bracts had mainly peltate and capitate glandular trichomes as well as stellate non-glandular trichomes (in V. lantana). The trichomes were shown to contain lipids, mucilage, and tannins. Many similarities in the flower and nectaries microstructure and considerable heterogeneity were observed in the examined Viburnum species. Knowledge of the microstructural characteristics of flowers, nectaries, and trichomes may be important for the phylogenesis and taxonomy of the genus Viburnum and the family Adoxaceae. Additionally, floral and nectaries features are helpful in assessment of the relatedness between taxa and provide better understanding of the floral biology and pollination ecology.

In vitro flowering, glandular trichomes ultrastructure, and essential oil accumulation in micropropagated Ocimum basilicum L.

The aromatic and medicinal properties of Ocimum basilicum L. (sweet basil) are related to the unique essential oil chemistry in different cultivars. This study describes efficient micropropagation and in vitro flowering protocols from shoot tips and reveals information on seed germination capability, glandular trichomes ultrastructure, and essential oil content and composition at different plant developmental stages from micropropagated O. basilicum ‘Sweet Thai’, chemotype methyl chavicol. Shoot tips from 2-mo-old aseptic seedlings were induced to proliferate shoots on Murashige and Skoog (MS) medium supplemented with 6-benzyl-aminopurine (BAP) and gibberellic acid (GA3) either alone or in combination with α-naphthaleneacetic acid (NAA). Maximum shoot formation was achieved in MS medium supplemented with 1.0 mg L−1 BAP. The micropropagated plants were successfully acclimatized ex vitro with an 80% survival rate. All of the micropropagated plants flowered in vitro on MS medium supplemented with 1.0 mg L−1 GA3. Relative to the mother plant, in vitro plants flowered at a younger stage of plant development but showed a lack of seed formation, fewer fully filled peltate glandular trichomes, lower essential oil content, and higher methyl chavicol content. Ex vitro plants flowered at an intermediate stage of plant development and formed seed with nearly the same seed germinability, essential oil content, and methyl chavicol content as the mother plant.

Ultrastructure of the epiphytic sooty mold Capnodium and surface-colonized walnut leaves

Cellular aspects of sooty mold on walnut leaves were investigated by using light and electron microscopy. A black coating developed on the adaxial surface of walnut leaves. No infestations were found on the abaxial leaf surface with peltate glandular trichomes. Light microscopy showed that fungal complexes from the leaf surface were composed of brown conidia and hyphae. Conidia, with longitudinal and transverse septa, were variable in length ranging from 10 to 30 μm, and commonly found in clusters, forming microsclerotia. Neither epidermal penetration nor hyphal entrance to host tissues was observed. Based on their morphological characteristics, the fungal complexes were assumed to be Capnodium species. An electron-dense melanized layer was present on the cell wall of multi-celled conidia. Concentric bodies in the fungal cytoplasm had an electron-translucent core surrounded by an electron-dense margin with a fibrillar sheath. Chloroplasts without starch granules in the palisade mesophyll cells of sooty leaves had electron-dense stromata and swollen plastoglobuli. These results suggest that the epiphytic growth of the sooty mold may be attributed to the melanized layer and concentric bodies against a water-deficient environment on the leaf surface. Ultrastructural characteristics of the sooty leaves indicate typical features of dark-adapted and non-photosynthetic shade leaves.

Metabolic engineering of terpene biosynthesis in plants using a trichome-specific transcription factor MsYABBY5 from spearmint (Mentha spicata).

SummaryIn many aromatic plants including spearmint (Mentha spicata), the sites of secondary metabolite production are tiny specialized structures called peltate glandular trichomes (PGT). Having high commercial values, these secondary metabolites are exploited largely as flavours, fragrances and pharmaceuticals. But, knowledge about transcription factors (TFs) that regulate secondary metabolism in PGT remains elusive. Understanding the role of TFs in secondary metabolism pathway will aid in metabolic engineering for increased yield of secondary metabolites and also the development of new production techniques for valuable metabolites. Here, we isolated and functionally characterized a novel MsYABBY5 gene that is preferentially expressed in PGT of spearmint. We generated transgenic plants in which MsYABBY5 was either overexpressed or silenced using RNA interference (RNAi). Analysis of the transgenic lines showed that the reduced expression of MsYABBY5 led to increased levels of terpenes and that overexpression decreased terpene levels. Additionally, ectopic expression of MsYABBY5 in Ocimum basilicum and Nicotiana sylvestris decreased secondary metabolite production in them, suggesting that the encoded transcription factor is probably a repressor of secondary metabolism.

Characterization of glandular trichomes in four Origanum vulgare L. accessions influenced by light reduction

The effect of reduced light intensity (minus 26%) on trichomes characteristics and herb yield responses of three subspecies of Origanum vulgare (ssp. vulgare , ssp. hirtum (Link) letswaart and ssp. viride (Boiss.) Hayek) and a hybrid (ssp. viride (Boiss.) Hayek x O. majorana L.) was investigated. It was found that the genotypes showed different morphological characteristics which were significantly influenced by light reduction. Reduced light intensity decreased the total indumentum of the leaf as well as the density and size of capitate glandular trichomes and size of peltate glandular trichomes. It also decreased the theoretical volume of essential oil on one peltate glandular trichome as well as the total theoretical volume of essential oil on adaxial side of one leaf. The indumentum of all samples included non-glandular trichomes, peltate glandular trichomes and capitate glandular trichomes type I. Capitate glandular trichomes type II with low density were observed only on O. vulgare ssp. viride and on the hybrid. It can be suggested that the applied light reduction was a limiting factor for the growth of O. vulgare L. plants. Reduced light shifted the carbon allocation to increase plant surfaces and therefore resulted in reduction of trichomes density of O. vulgare L.

Erratum to: Distribution, morphological and histochemical characteristics of foliar trichomes of Plectranthus zuluensis (Lamiaceae)

There are problems in the delimitation/identification of Plectranthus species and this investigation aims to contribute toward solving such problems through structural and histochemical study of the trichomes. Considering the importance of P. zuluensis as restricted to semi-coastal forests of Natal that possess only two fertile stamens not four as the other species of this genus. The objective of this work was to study in detail the distribution, morphology and histochemistry of the foliar trichomes of this species using light and electron microscopy. Distribution and morphology of two types of non-glandular, capitate and peltate glandular trichomes are described on both leaf sides. This study provides a description of the different secretion modes of glandular trichomes. Results of histochemical tests showed a positive reaction to terpenoids, lipids, polysaccharides and phenolics in the glandular trichomes. We demonstrated that the presence, types and structure of glandular and non-glandular trichomes are important systematic criteria for the species delimitation in the genus.

The exploitation of micromorphological parameters for identification in the section / Mentha Využitie mikromorfologických parametrov pri identifikácii v sekcii Mentha

Abstract The identification of species in the genus Mentha is especially difficult because of the ease of hybridization, favoured by gynodioecy, which is further complicated by polymorphism, cultivation, polyploidy and vegetative propagation. This all explains the genicpopulation and microevolutionary background for variability of mints. In this work we studied the usage of micromorphological and phytochemical parameters in identification and characterization of selected Mentha species. On abaxial surface of leaves of 20 Mentha populations we determined the size and the number of peltate glandular trichomes. The essential oil was analysed by GC MS. We identified and characterized populations of M. × piperita, M. spicata, M. spicata subsp. condensata, M. spicata var. crispa, M. spicata var. citrata, M. × gentilis, M. aquatic, M. arvensis amd M. longifolia. The size and the number of peltate glandular trichomes contribute to characterisation of some Mentha species (especially in M. longifolia and M. × piperita).

The key role of peltate glandular trichomes in symbiota comprising clavicipitaceous fungi of the genus periglandula and their host plants.

Clavicipitaceous fungi producing ergot alkaloids were recently discovered to be epibiotically associated with peltate glandular trichomes of Ipomoea asarifolia and Turbina corymbosa, dicotyledonous plants of the family Convolvulaceae. Mediators of the close association between fungi and trichomes may be sesquiterpenes, main components in the volatile oil of different convolvulaceous plants. Molecular biological studies and microscopic investigations led to the observation that the trichomes do not only secrete sesquiterpenes and palmitic acid but also seem to absorb ergot alkaloids from the epibiotic fungal species of the genus Periglandula. Thus, the trichomes are likely to have a dual and key function in a metabolic dialogue between fungus and host plant.

Peltate glandular trichomes of Colquhounia seguinii harbor new defensive clerodane diterpenoids.

Glandular trichomes produce a wide variety of secondary metabolites that are considered as major defensive chemicals against herbivore attack. The morphology and secondary metabolites of the peltate glandular trichomes of a lianoid Labiatae, Colquhounia seguinii Vaniot, were investigated. Three new clerodane diterpenoids, seguiniilactones A-C (1-3), were identified through precise trichome collection with laser microdissection, metabolic analysis with ultra performance liquid chromatography-tandem mass spectrometer, target compound isolation with classical phytochemical techniques, structure elucidation with spectroscopic methods. All compounds showed significant antifeedant activity against a generalist plant-feeding insect Spodoptera exigua. Seguiniilactone A (1) was approximately 17-fold more potent than the commercial neem oil. α-Substituted α,β-unsaturated γ-lactone functionality was found to be crucial for strong antifeedant activity of this class of compounds. Quantitative results indicated that the levels of these compounds in the peltate glandular trichomes and leaves were sufficiently high to deter the feeding by generalist insects. Moderate antifungal activity was observed for seguiniilactone C (3) against six predominant fungal species isolated from the diseased leaves of C. seguinii, while seguiniilactones A and B were generally inactive. These findings suggested that seguiniilactones A-C might be specialized secondary metabolites in peltate glandular trichomes for the plant defense against insect herbivores and pathogens.

Characterization of Satureja khuzestanica leaf as a herbal medicine.

Dried leaves of Satureja khuzestanica Jamzad are a popular herbal medicine and dental anesthetic among the nomadic inhabitants of southwestern Iran. The present study establishes criteria for identification of S. khuzestanica dried whole, fragmented and powdered leaves for specification as a herbal substance using macroscopic and microscopic characterization. Quantitative microscopy techniques were also considered. Macroscopically leaves exhibit a grayish-green color, are broadly ovate in shape with an acute apex, attenuate base, and ciliate margin and have a surface covered by an indumentum of glandular and non-glandular trichomes. Microscopically leaves have an isobilateral amphistomatic structure containing peltate glandular trichomes consisting of a multiseriate stalk (five cells) and an enlarged secretory head composed of 12 cells, capitate glandular trichomes of variable morphology together with two types of non-glandular trichomes. Oval-shaped hygromorphic diacytic stomata with an adaxial stomatal index of 13.54, collateral vascular bundles consisting of xylem, and three layers of sclerenchymatous tissue close to phloem together with cluster, prismatic and raphide calcium oxalate crystals were also identified as useful pharmacognostic parameters for identification of S. khuzestanica dried leaves.

Comparative investigation about the trichome morphology of Common oregano (Origanum vulgare L. subsp. vulgare) and Greek oregano (Origanum vulgare L. subsp. hirtum)

The genus Origanum is divided in several species and subspecies. Common oregano (Origanum vulgare L. subsp. vulgare) and Greek oregano (Origanum vulgare L. subsp. hirtum) are two important subspecies which are characterized by different content of essential oil synthesized in glandular trichomes. Investigations with light microscopy and scanning electron microscopy were carried out to determine the morphological parameters of the leaves and trichomes of O. vulgare subspecies cultivated in a pot experiment under field conditions. It was found that Greek oregano is characterized by higher density of peltate as well as capitate glandular trichomes on adaxial leaf side compared to common oregano. The size of peltate glandular trichomes of Greek oregano was significantly larger on both sides (abaxial and adaxial) of the leaves compared to common oregano whereas no difference between both subspecies was observed regarding the size of capitate glandular trichomes. It can be concluded that higher essential oil content of Greek oregano is caused by the combination of both higher density and larger size (larger volume) of peltate glandular trichomes.