Density Of Glandular Trichomes Research Articles

Interactive effect of biogenic nanoparticles and UV-B exposure on physio-biochemical behavior and secondary metabolism of Artemisia annua L

Biosynthesized silver nanoparticles (AgNPs) are key nanomaterials with unique physio-chemical characteristics and diverse applications. Their strong absorption potential and antibacterial activity make them useful for agriculture, medicine and other industries. AgNPs boost plant growth and metabolism, especially under stress. However, the combined effects of AgNPs and UV-B exposure on plants are unknown. To elucidate the interactive effects of biosynthesized silver nanoparticles (AgNPs) and exposure of ultraviolet B (UV-B) on plant growth and metabolic processes, this study assessed the response of Artemisia annua under controlled in vitro conditions. In total, eight sets of plants were used with the alone/combined treatment of AgNPs and UV-B. For this purpose, spherical and averaged ∼ 31.8 nm in size AaAgNPs were synthesized. The photosynthetic pigments were calculated maximum with the alone treatment of 0.5 mg L−1 AaAgNPs and combined treatment of 0.5 mg L−1 AaAgNPs with 3 h UV-B, respectively. The results evidenced that the co-exposure of AaAgNPs and UV-B led to a significant balance in ROS production of A. annua; as well as improved antioxidative enzyme activity. Fluorescence and scanning electron microscopic (SEM) analysis indicated the enhancement of glandular trichomes (GT) area and density with the combined treatment of AaAgNPs and 3 h UV-B. In accordance with correlation between microscopic GT results, high concentration of artemisinin and up-regulation of related transcripts were found in A. annua plants treated with low concentrations of AaAgNPs and UV-B. Thus, it may be inferred that two distinct plant growth modulators, namely low-concentration biosynthesized AgNPs and short-term UV-B exposure, can enhance the physio-biochemical characteristics and production of secondary metabolites (specially artemisinin) in A. annua synergistically.

Genome-wide investigation of WRKY gene family in Lavandula angustifolia and potential role of LaWRKY57 and LaWRKY75 in the regulation of terpenoid biosynthesis.

The WRKY transcription factors are integral to plant biology, serving essential functions in growth, development, stress responses, and the control of secondary metabolism. Through the use of bioinformatics techniques, this research has effectively characterized 207 members of the WRKY family (LaWRKY) present in the entire genome of Lavandula angustifolia. Phylogenetic analysis classified LaWRKYs into three distinct categories based on conserved domains. Collinearity analysis revealed tandem repeats, segmental duplications, and whole genome duplications in LaWRKYs, especially for segmental duplication playing a significant role in gene family expansion. LaWRKYs displayed distinct tissue-specific expression profiles across six different tissues of L. angustifolia. Particularly noteworthy were 12 genes exhibiting high expression in flower buds and calyx, the primary sites of volatile terpenoid production, indicating their potential role in terpenoid biosynthesis in L. angustifolia. RT-qPCR analysis revealed a notable increase in the expression levels of most examined LaWRKY genes in flower buds in response to both intense light and low-temperature conditions, whereas the majority of these genes in leaves were primarily induced by drought stress. However, all genes exhibited downregulation following GA treatment in both flower buds and leaves. Overexpression of LaWRKY57 (La13G01665) and LaWRKY75 (La16G00030) in tobacco led to a reduction in the density of glandular trichomes on leaf surfaces, resulting in changes to the volatile terpenoid composition in the leaves. Specifically, the content of Neophytadiene was significantly elevated compared to wild-type tobacco, while compounds such as eucalyptol, cis-3-Hexenyl iso-butyrate, and D-Limonene were produced, which were absent in the wild type. These findings provide a valuable reference for future investigations into the biological functions of the WRKY gene family in L. angustifolia.

Morphological Parameters of Sesame in Relation to Susceptibility to Major Sucking Insect Pests

Based on previous field screening data 15 genotypes were selected (based on the number of insect pests population/ plant) to study the role of morphological parameters of sesame. Trichome density, length and width were estimated under microscope with the help of software. The 15 selected genotypes of sesame were studied for finding trichome’s role in host plant resistance against major sucking pests; whitefly Bemisia tabaci), leafhopper (Orocius albicinctus) and mirid bug (Nesidiocoris tenuis) of sesame and the correlation studies revealed that the density of non-glandular trichome showed significant positive correlation with the population of Orocius albicinctus (r= 0.868), Nesidiocoris tenuis (r=0.549) and Bemisia tabaci (r= 0.824) while length and width of non-glandular trichomes and density of glandular trichomes showed non-significant (±) impact on the incidence of tested sucking insect pests.

Artemisia annua ZFP8L regulates glandular trichome development.

Trichomes are known to be important biofactories that contribute to the production of secondary metabolites, such as terpenoids. C2H2-zinc finger proteins (C2H2-ZFPs) are vital transcription factors of plants' trichome development. However, little is known about the function of Artemisia annua C2H2-ZFPs in trichome development. To explore the roles of this gene family in trichome development, two C2H2-ZFP transcription factors, named AaZFP8L and AaGIS3, were identified; both are hormonally regulated in A. annua. Overexpression of AaZFP8L in tobacco led to a significant increase in the density and length of glandular trichomes, and improved terpenoid content. In contrast, AaGIS3 was found to positively regulate non-glandular trichome initiation and elongation, which reduces terpenoid accumulation. In addition, ABA contents significantly increased in AaZFP8L-overexpressing tobacco lines and AaZFP8L also can directly bind the promoter of the ABA biosynthesis genes. This study lays the foundation for further investigating A. annua C2H2-ZFPs in trichome development and terpenoid accumulation.

Characteristics of the phyllosphere microbial community and its relationship with major aroma precursors during the tobacco maturation process.

Numerous bacteria, fungi and other microorganisms in the tobacco phyllosphere interstellar area participate in the physiological metabolism of plants by interacting with the host. However, there is currently little research on the characteristics of tobacco phyllosphere microbial communities, and the correlation between tobacco phyllosphere microbial communities and phyllosphere factor indicators is still unknown. Therefore, high-throughput sequencing technology based on the 16S rRNA/ITS1 gene was used to explore the diversity and composition characteristics of tobacco phyllosphere bacterial and fungal communities from different maturation processes, and to identify marker genera that distinguish phyllosphere microbial communities. In this study, the correlations between tobacco phyllosphere bacterial and fungal communities and the precursors of major aroma compounds were explored. The results showed that as the tobacco plants matured, the density of glandular trichomes on the tobacco leaves gradually decreased. The surface physicochemical properties of tobacco leaves also undergo significant changes. In addition, the overall bacterial alpha diversity in the tobacco phyllosphere area increased with maturation, while the overall fungal alpha diversity decreased. The beta diversity of bacteria and fungi in the tobacco phyllosphere area also showed significant differences. Specifically, with later top pruning time, the relative abundances of Acidisoma, Ralstonia, Bradyrhizobium, Alternaria and Talaromyces gradually increased, while the relative abundances of Pseudomonas, Filobassidium, and Tausonia gradually decreased. In the bacterial community, Acidisoma, Ralstonia, Bradyrhizobium, and Alternaria were significantly positively correlated with tobacco aroma precursors, with significant negative correlations with tobacco phyllosphere trichome morphology, while Pseudomonas showed the opposite pattern; In the fungal community, Filobasidium and Tausonia were significantly negatively correlated with tobacco aroma precursors, and significantly positively correlated with tobacco phyllosphere trichome morphology, while Alternaria showed the opposite pattern. In conclusion, the microbiota (bacteria and fungi) and aroma precursors of the tobacco phyllosphere change significantly as tobacco matures. The presence of Acidisoma, Ralstonia, Bradyrhizobium and Alternaria in the phyllosphere microbiota of tobacco may be related to the aroma precursors of tobacco.

Leaf morpho-anatomical adjustments in a Quercus pubescens forest after 10 years of partial rain exclusion in the field.

In the Mediterranean region, a reduction of annual precipitation and a longer and drier summer season are expected with climate change by the end of the century, eventually endangering forest survival. To cope with such rapid changes, trees may modulate their morpho-anatomical and physiological traits. In the present study, we focused on the variation in leaf gas exchange and different leaf morpho-anatomical functional traits of Quercus pubescens Willd. in summer using a long-term drought experiment in natura consisting of a dynamic rainfall exclusion system where trees have been submitted to amplified drought (AD) (~-30% of annual precipitation) since April 2012 and compared them with trees under natural drought (ND) in a Mediterranean forest. During the study, we analyzed net CO2 assimilation (An), stomatal conductance (gs), transpiration (E), water-use efficiency (WUE), stomatal size and density, density of glandular trichomes and non-glandular trichomes, thickness of the different leaf tissues, specific leaf area and leaf surface. Under AD, tree functioning was slightly impacted, since only An exhibited a 49% drop, while gs, E and WUE remained stable. The decrease in An under AD was regulated by concomitant lower stomatal density and reduced leaf thickness. Trees under AD also featured leaves with a higher non-glandular trichome density and a lower glandular trichome density compared with ND, which simultaneously limits transpiration and production costs. This study points out that Q. pubescens exhibits adjustments of leaf morpho-anatomical traits which can help trees to acclimate to AD scenarios as those expected in the future in the Mediterranean region.

Chromium stress influences several parameters of leaf dynamics and morphology in Oryza sativa L. genotypes

Chromium (Cr) stress is a prevalent abiotic stress that alters various physiological, growth and metabolic parameters in plants. The toxicity of chromium at concentrations up to 100 µM were studied in two common Indian Oryza sativa genotypes, Lalat upland and Swarnaprabha. More chromium accumulated in roots than in leaves in both genotypes, with Lalat upland taking up more chromium than Swarnaprabha. Higher chromium concentrations reduced various physiological traits including stomatal conductance, transpiration rate, photosynthetic water use efficiency, photosynthetic pigments content in both the genotypes, and this decline was more pronounced in Lalat upland. Increase in vapour pressure deficit, sub stomatal carbon dioxide concentration and malondialdehyde content was detected at 100 µM chromium treated genotypes, however the effects were higher in Lalat upland. Confocal microscopy showed stomatal guard cell deformation, greater stomatal area and closed stomatal aperture in the leaves of 100 µM chromium treated Lalat upland plants. Abscisic acid and Salicylic acid content and expression of NCED1 and NCED2 genes involved in stomata aperture regulation were enhanced in Lalat upland and down regulated in Swarnaprabha under chromium stress. Variation in glandular and non-glandular trichome density and length was found in the leaves of chromium stressed plants in both the genotypes. The results suggest that Lalat upland is more sensitive to chromium toxicity than Swarnaprabha at higher chromium concentrations.

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

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

Advanced metabolic engineering strategies for increasing artemisinin yield in Artemisia annua L.

Artemisinin, also known as 'Qinghaosu', is a chemically sesquiterpene lactone containing an endoperoxide bridge. Due to the high activity to kill Plasmodium parasites, artemisinin and its derivatives have continuously served as the foundation for antimalarial therapies. Natural artemisinin is unique to the traditional Chinese medicinal plant Artemisia annua L., and its content in this plant is low. This has motivated the synthesis of this bioactive compound using yeast, tobacco, and Physcomitrium patens systems. However, the artemisinin production in these heterologous hosts is low and cannot fulfil its increasing clinical demand. Therefore, A. annua plants remain the major source of this bioactive component. Recently, the transcriptional regulatory networks related to artemisinin biosynthesis and glandular trichome formation have been extensively studied in A. annua. Various strategies including (i) enhancing the metabolic flux in artemisinin biosynthetic pathway; (ii) blocking competition branch pathways; (iii) using transcription factors (TFs); (iv) increasing peltate glandular secretory trichome (GST) density; (v) applying exogenous factors; and (vi) phytohormones have been used to improve artemisinin yields. Here we summarize recent scientific advances and achievements in artemisinin metabolic engineering, and discuss prospects in the development of high-artemisinin yielding A. annua varieties. This review provides new insights into revealing the transcriptional regulatory networks of other high-value plant-derived natural compounds (e.g., taxol, vinblastine, and camptothecin), as well as glandular trichome formation. It is also helpful for the researchers who intend to promote natural compounds production in other plants species.

Comportamento de oviposição e consumo foliar de Chrysodeixis includens (Lepidoptera: Noctuidae) em genótipos de soja

ABSTRACT: The use of plant resistance acts by intervening in the herbivore-host relationship, through morphological, physical or chemical factors of the plant. This study evaluated the oviposition and foliar consumption of Chrysodeixis includens (Walker [1858]) in soybean genotypes, in free- and no-choice tests, correlating them with the factors, density and size of trichomes. The experiments were carried out in laboratory (25 ± 2 °C; RH= 70 ± 10%; photoperiod 14h) using five cultivars (BRS 391, BRS 6203 RR, BMX Valente RR, Tec Irga 6070 RR, BMX Icone Ipro) and two isolines (PELBR 10-6000 and PELBR 10-6049). The trichomes reported were filiform tectors and claviform multicellular glandular. The density of glandular trichomes, in stages V2 and V5, was higher on BRS 6203 RR and BRS 391, respectively. The higher density of glandular trichomes was observed in V5 and a higher density of tector trichomes in V2. The lowest densities and the smallest sizes of trichomes in V2 and V5 stages was observed on PELBR 10-6049. The size of tector trichomes and the number of eggs did not differ among the cultivars. Foliar consumption was lower for on BMX Icone Ipro and Tec Irga 6070 RR. Trichome density influences the consumption and oviposition behavior of C. includens.

Glandular trichomes as a source of antifungal metabolites in a karyologically characterized population of Argyrochosma flava: Morphology and histochemistry

Argyrochosma, a xeric-adapted fern genus mostly from the New World, includes both farinose and non-farinose species. The yellow farina appears to be a synapomorphy of A. flava. The aims of this research were to study the morphology, location, distribution, and density of glandular trichomes; perform a histochemical analysis of the farina secretion; evaluate the biological activity of farinas against phytopathogenic fungi; and characterize the species genetically by making chromosome counts and building the karyotype of A. flava. Usual methods in plant anatomy and histochemistry were performed. Minimum Inhibitory Concentrations (MICs) and Minimum Fungicidal Concentrations (MFCs) of farina against four phytopathogenic fungi were determined by the broth microdilution technique. Chromosome counts and karyotyping metaphase plates were obtained from fiddleheads. The distribution of glandular trichomes in pinnules changes along the ontogenetic development of the frond. The histochemical study of the trichomes revealed the complex nature of the secreted material, including flavonoids and terpenes along with other metabolites. The farina was active against the four pathogenic fungi evaluated, with MICs between 31.25 and 125 μg/mL showing the highest inhibition for Monilinia fructicola. Botrytis cinerea displayed a MIC value of only one-fold dilutions more than the commercial fungicide Carbendazim. Cytogenetically, the base number proposed for the genus is x = 27, which is derived from aneuploidy of x = 29. The genus has diploid and tetraploid forms. The results obtained support the important role of glandular trichomes and farinous exudate secretion in the protection against phytopathogenic fungi. The obtained chromosome numbers support the taxonomic placement of A. flava.

AaABCG20 transporter involved in cutin and wax secretion affects the initiation and development of glandular trichomes in Artemisia annua

Glandular trichomes are specialized structures found on the surface of plants to produce specific compounds, including terpenes, alkaloids, and other organic substances. Artemisia annua, commonly known as sweet wormwood, synthesizes and stores the antimalarial drug artemisinin in glandular trichomes. Previous research indicated that increasing the glandular trichome density could enhance artemisinin production, and the cuticle synthesis affected the initiation and development of glandular trichomes in A. annua. In this study, AaABCG12 and AaABCG20 were isolated from A. annua that exhibited similar expression patterns to artemisinin biosynthetic genes. Of the two, AaABCG20 acted as a specific transporter in glandular trichomes. Downregulating the expression of AaABCG20 resulted in a notable reduction in the density of glandular trichome, while overexpressing AaABCG20 resulted in an increase in glandular trichome density. GC-MS analysis demonstrated that AaABCG20 was responsible for the transport of cutin and wax in A. annua. These findings indicated that AaABCG20 influenced the initiation and development of glandular trichomes through transporting cutin and wax in A. annua. This glandular trichome specific half-size ABCG-type transporter is crucial in facilitating the transportation of cutin and wax components, ultimately contributing to the successful initiation and development of glandular trichomes.

Effect of salinity on glandular trichomes density, phenolic and flavonoid contents of Morus spp. accessions leaves from Indonesia

The density of glandular trichomes and metabolite compounds in plants can increase under salt stress. Information about the glandular trichomes density described tolerance to salt stress however, there is no information about it in mulberry. This study aimed to obtain accessions of mulberry that are tolerant to NaCl concentrations based on cystolith trichome density, glandular trichome density, and phenolic and flavonoid content. Mulberry stem cuttings were planted using a factorial randomized block design with 3 replications. The first treatment used was seven mulberry accessions, which come from 5 regions in Indonesia (Bali, Makassar, Pati, Situbondo, and Bogor), and the second was the NaCl concentration (0.0%, 0.2%, 0.3%, and 0.4%). The results showed that the highest cystolith trichomes density was obtained in M2 accession (32.5 cells/mm2 from the highest NaCl concentration). The highest density of the glandular trichomes was obtained in the M4 accession (50 cells/mm2 from the highest NaCl concentration). The highest phenolic and flavonoid contents were obtained in the M4 accession (154.6 mg GAE/g extract for 0.3% concentration of NaCl) and M2 accession (619.56 mg QE/g extract for the highest concentration of NaCl), respectively. The study concluded that the M2 (accession from Bogor) is tolerant to salt stress.

Acclimation of subarctic vegetation to warming and increased cloudiness.

Subarctic ecosystems are exposed to elevated temperatures and increased cloudiness in a changing climate with potentially important effects on vegetation structure, composition, and ecosystem functioning. We investigated the individual and combined effects of warming and increased cloudiness on vegetation greenness and cover in mesocosms from two tundra and one palsa mire ecosystems kept under strict environmental control in climate chambers. We also investigated leaf anatomical and biochemical traits of four dominant vascular plant species (Empetrum hermaphroditum, Vaccinium myrtillus, Vaccinium vitis-idaea, and Rubus chamaemorus). Vegetation greenness increased in response to warming in all sites and in response to increased cloudiness in the tundra sites but without associated increases in vegetation cover or biomass, except that E. hermaphroditum biomass increased under warming. The combined warming and increased cloudiness treatment had an additive effect on vegetation greenness in all sites. It also increased the cover of graminoids and forbs in one of the tundra sites. Warming increased leaf dry mass per area of V. myrtillus and R. chamaemorus, and glandular trichome density of V. myrtillus and decreased spongy intercellular space of E. hermaphroditum and V. vitis-idaea. Increased cloudiness decreased leaf dry mass per area of V. myrtillus, palisade thickness of E. hermaphroditum, and stomata density of E. hermaphroditum and V. vitis-idaea, and increased leaf area and epidermis thickness of V. myrtillus, leaf shape index and nitrogen of E. hermaphroditum, and palisade intercellular space of V. vitis-idaea. The combined treatment caused thinner leaves and decreased leaf carbon for V. myrtillus, and increased leaf chlorophyll of E. hermaphroditum. We show that under future warmer increased cloudiness conditions in the Subarctic (as simulated in our experiment), vegetation composition and distribution will change, mostly dominated by graminoids and forbs. These changes will depend on the responses of leaf anatomical and biochemical traits and will likely impact carbon gain and primary productivity and abiotic and biotic stress tolerance.

Yeast extract and chitosan elicitation improves essential oil, regulates plant growth and antioxidative system in Lippia alba (Mill) N.E. Brown (Verbenaceae)

Lippia alba is one of the most used species in traditional medicine, having been the subject of intense exploration in search of the extraction of its essential oil, which contains several compounds of pharmacological importance. This study evaluated the effects of different concentrations of two biotic elicitors: yeast extract (YE) (0, 1, 2 and 4 g L−1) and chitosan (CH) (0, 1, 2 and 4 g L−1) in the accumulation of biomass, gas exchange, antioxidative system response, and production and profile of bioactive compounds (BCs). Foliar spraying with 4 g L−1 of CH favored the accumulation of shoot dry biomass and significantly increased the levels of chlorophyll a and carotenoids. Both elicitors were efficient to increase the essential oil content extracted from the leaves of L. alba and, in general, the elicitors tested at concentrations of 2 and 4 g L−1 showed the highest amounts of BCs and glandular trichome density. Chemical analysis of BCs revealed 46 different compounds, with Geranial and Geraniol being the main components. The application of YE induced the production of an exclusive compound (Trans-piperitol), while CH induced the formation of seven exclusive compounds (Santolina triene, Myrcenol, Neral, Cis-Pinocarvyl acetate, Dimethoxy-(Z)-citral, Geranyl acetate and Limonene aldehyde). Yeast extract and Chitosan proved to be efficient to increase the BCs content in Lippia alba, however, the application of 4 g L−1 of CH resulted in a higher production of shoot dry biomass, photosynthetic parameters, in the density of glandular trichomes and in the production of BCs.

Graphene enhances artemisinin production in the traditional medicinal plant Artemisia annua via dynamic physiological processes and miRNA regulation

We investigated the effects of graphene on the model herb Artemisia annua, which is renowned for producing artemisinin, a widely used pharmacological compound. Seedling growth and biomass were promoted when A. annua was cultivated with low concentrations of graphene, an effect which was attributed to a 1.4-fold increase in nitrogen uptake, a 15%–22% increase in chlorophyll fluorescence, and greater abundance of carbon cycling–related bacteria. Exposure to 10 or 20 mg/L graphene resulted in a ∼60% increase in H2O2, and graphene could act as a catalyst accelerator, leading to a 9-fold increase in catalase (CAT) activity in vitro and thereby maintaining reactive oxygen species (ROS) homeostasis. Importantly, graphene exposure led to an 80% increase in the density of glandular secreting trichomes (GSTs), in which artemisinin is biosynthesized and stored. This contributed to a 5% increase in artemisinin content in mature leaves. Interestingly, expression of miR828 was reduced by both graphene and H2O2 treatments, resulting in induction of its target gene AaMYB17, a positive regulator of GST initiation. Subsequent molecular and genetic assays showed that graphene-induced H2O2 inhibits micro-RNA (miRNA) biogenesis through Dicers and regulates the miR828–AaMYB17 module, thus affecting GST density. Our results suggest that graphene may contribute to yield improvement in A. annua via dynamic physiological processes together with miRNA regulation, and it may thus represent a new cultivation strategy for increasing yield capacity through nanobiotechnology.

Comparative genomics of flowering behavior in Cannabis sativa.

Cannabis sativa L. is a phenotypically diverse and multi-use plant used in the production of fiber, seed, oils, and a class of specialized metabolites known as phytocannabinoids. The last decade has seen a rapid increase in the licit cultivation and processing of C. sativa for medical end-use. Medical morphotypes produce highly branched compact inflorescences which support a high density of glandular trichomes, specialized epidermal hair-like structures that are the site of phytocannabinoid biosynthesis and accumulation. While there is a focus on the regulation of phytocannabinoid pathways, the genetic determinants that govern flowering time and inflorescence structure in C. sativa are less well-defined but equally important. Understanding the molecular mechanisms that underly flowering behavior is key to maximizing phytocannabinoid production. The genetic basis of flowering regulation in C. sativa has been examined using genome-wide association studies, quantitative trait loci mapping and selection analysis, although the lack of a consistent reference genome has confounded attempts to directly compare candidate loci. Here we review the existing knowledge of flowering time control in C. sativa, and, using a common reference genome, we generate an integrated map. The co-location of known and putative flowering time loci within this resource will be essential to improve the understanding of C. sativa phenology.

The non-specific lipid transfer protein McLTPII.9 of Mentha canadensis is involved in peltate glandular trichome density and volatile compound metabolism.

Mentha canadensis L. is an important spice crop and medicinal herb with high economic value. The plant is covered with peltate glandular trichomes, which are responsible for the biosynthesis and secretion of volatile oils. Plant non-specific lipid transfer proteins (nsLTPs) belong to a complex multigenic family involved in various plant physiological processes. Here, we cloned and identified a non-specific lipid transfer protein gene (McLTPII.9) from M. canadensis, which may positively regulate peltate glandular trichome density and monoterpene metabolism. McLTPII.9 was expressed in most M. canadensis tissues. The GUS signal driven by the McLTPII.9 promoter in transgenic Nicotiana tabacum was observed in stems, leaves, and roots; it was also expressed in trichomes. McLTPII.9 was associated with the plasma membrane. Overexpression of McLTPII.9 in peppermint (Mentha piperita. L) significantly increased the peltate glandular trichome density and total volatile compound content compared with wild-type peppermint; it also altered the volatile oil composition. In McLTPII.9-overexpressing (OE) peppermint, the expression levels of several monoterpenoid synthase genes and glandular trichome development-related transcription factors-such as limonene synthase (LS), limonene-3-hydroxylase (L3OH), geranyl diphosphate synthase (GPPS), HD-ZIP3, and MIXTA-exhibited varying degrees of alteration. McLTPII.9 overexpression resulted in both a change in expression of genes for terpenoid biosynthetic pathways which corresponded with an altered terpenoid profile in OE plants. In addition, peltate glandular trichome density was altered in the OE plants as well as the expression of genes for transcription factors that were shown to be involved in trichome development in plants.

Creation of New Oregano Genotypes with Different Terpene Chemotypes via Inter- and Intraspecific Hybridization.

Oregano is a medicinal and aromatic plant of value in the pharmaceutical, food, feed additive, and cosmetic industries. Oregano breeding is still in its infancy compared with traditional crops. In this study, we evaluated the phenotypes of 12 oregano genotypes and generated F1 progenies by hybridization. The density of leaf glandular secretory trichomes and the essential oil yield in the 12 oregano genotypes varied from 97-1017 per cm2 and 0.17-1.67%, respectively. These genotypes were divided into four terpene chemotypes: carvacrol-, thymol-, germacrene D/β-caryophyllene-, and linalool/β-ocimene-type. Based on phenotypic data and considering terpene chemotypes as the main breeding goal, six oregano hybrid combinations were performed. Simple sequence repeat (SSR) markers were developed based on unpublished whole-genome sequencing data of Origanum vulgare, and 64 codominant SSR primers were screened on the parents of the six oregano combinations. These codominant primers were used to determine the authenticity of 40 F1 lines, and 37 true hybrids were identified. These 37 F1 lines were divided into six terpene chemotypes: sabinene-, β-ocimene-, γ-terpinene-, thymol-, carvacrol-, and p-cymene-type, four of which (sabinene-, β-ocimene-, γ-terpinene-, and p-cymene-type) were novel (i.e., different from the chemotypes of parents). The terpene contents of 18 of the 37 F1 lines were higher than those of their parents. The above results lay a strong foundation for the creating of new germplasm resources, constructing of genetic linkage map, and mapping quantitative trait loci (QTLs) of key horticultural traits, and provide insights into the mechanism of terpenoid biosynthesis in oregano.

Morphological studies of developing glandular trichomes and a novel HD-ZIP gene LjROC3 increasing glandular trichome density on leaves in honeysuckle (Lonicera japonica)

Glandular trichomes (GTs) of Lonicera japonica are the exocrine structure containing many medicinally active ingredients and essential oil. In this study, the GTs distribution in the shooting of honeysuckle was observed. On the leaf surface, GTs were mainly distributed along the prominent veins and decreased from the base to the tip, and their density gradually decreased with the development of leaves. However, GTs were evenly distributed on the stem surface, and their density first increased and then decreased as the stem continued to develop. Then, scanning electron microscopy (SEM) and paraffin sectioning (PS) were employed to identify the morphological structure and types of GTs. All GTs in L. japonica were first found to contain a disc-shaped base surrounding the basal cell and were newly named disc-pedestal capitate GT. Here, we also identified and compared the functions of two novel HD-ZIP genes designated as LjROC3 and LjHD-ZIP1. During GT development, these two HD-ZIP genes were both up-regulated. In addition, the heterologous expression and virus-induced gene silencing (VIGS) of LjROC3 increased and decreased the density of GTs, respectively, whereas the transformed lines of LjHD-ZIP1 showed no significant differences. Furthermore, the molecular mechanism of LjROC3 was analyzed using qRT-PCR in silencing lines. These results will provide valuable references for timely picking high metabolite medicinal materials, exploring the regulatory mechanism of GT development, and breeding new varieties with high GT density in L. japonica.