Biotransformation of Sclareol by a Fungal Endophyte of Salvia sclarea

Microbial endophytes are known as versatile producers of useful metabolites, which have extensive applications in pharmacy, fragrance, agriculture and food. This study aims to screen sclareol-biotransforming microorganisms from Salvia sclarea, an untapped source of diverse endophytes. In this study, 50 culturable endophytes were isolated from S. sclarea grown in Xinjiang using sclareol as the sole carbon source and screened for their potential to transform sclareol into analogues. A fungal endophyte, identified as the generally recognized as safe (GRAS) strain Aspergillus tubingensis, can produce labd-14-ene-3β,8α,13β-triol and 8α,13β-dihydroxylabd-14-en-3-one from sclareol, involving hydroxylation and carbonylation at the C3 site. Structures of the two metabolites were elucidated by HR-ESI-MS and NMR analysis. S. sclarea was proven to be a good source of endophytes that are prospective producers of secondary metabolites with valuable chemical and biological properties. This study is the first report regarding the isolation of endophytes from S. sclarea.

Data regarding anti-quorum sensing and antimicrobial activity of Melaleuca alternifolia and Salvia sclarea essential oil against Pseudomonas aeruginosa

To combat the increasing number of multi-drug resistant bacteria, researchers are now looking for alternatives that reduce the virulence and pathogenic potential of the bacteria without killing it. It can be accomplished by interfering with the quorum sensing (QS) system of bacteria. In this article, we aim to determine the antimicrobial and anti-QS activity of Salvia sclarea and Melaleuca alternifolia essential oils (EOs) against Pseudomonas aeruginosa. The sub-lethal concentration of these EOs was found with the help of a growth curve, and further experiments were carried out below this concentration. To check for their anti-quorum activity, a bioreporter strain E. coli pJN105LpSC11 (to measure the concentration of 3-oxo-C_12-HSL) and Chromobacterium violaceum CV026 (to check for the reduction in the formation of violacein pigment) was used. Several virulence phenotype assays like pyocyanin, alginate, and protease production, along with swarming motility, were done. The effect of these EOs on biofilm formation was also checked. The results were confirmed by checking the expression of genes by real-time PCR.

Chromatographic profiles and antimicrobial activity of the essential oils obtained from some species and cultivars of the Mentheae tribe (Lamiaceae)

The present study was focused on the chemical composition and antimicrobial activity of the essential oils (EsO) obtained from five Lamiaceae representatives grown in the south of Ukraine. Among them are Salvia sclarea L., Monarda didyma (cultivar ‘Cambridge Scarlet’), Thymus pulegioides (cultivar ‘2/6-07’), Thymus vulgaris (cultivar ‘Jalos’), and Thymus serpyllum L. The component analysis of the EsO was carried out by gas chromatography method coupled with mass spectrometry (GC–MS). The antimicrobial properties of the EsO were determined using the agar diffusion test against widespread pathogenic bacterial strains (Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Streptococcus pyogenes) and opportunistic yeast Candida albicans. The EsO of Thymus serpyllum and Thymus vulgaris (cultivar ‘Jalos’) displayed noteworthy antibacterial properties against a wide spectrum of the microorganisms. These antimicrobial properties could be attributed to the high content of aromatic monoterpenoid thymol (52.56% and 47.33%, respectively). The EsO of Salvia sclarea with the dominance of linalyl acetate (45.51%) and linalool (38.98%) as well as Thymus pulegioides (cultivar ‘2/6-07’) containing α-citral (27.10%) and β-citral (17.11%) demonstrated the strongest antimicrobial effects on typical and clinical strains of Staphylococcus aureus with the inhibition zones in the range of 24.0–31.0 mm. The Salvia sclarea EsO demonstrated the most significant effect against clinical strains of Candida albicans. In conclusion, the present study revealed the chemical composition of five Lamiaceae species and cultivars grown in the south of Ukraine and considerable antimicrobial activity of the tested EsO, especially against the typical and clinical strains of Staphylococcus aureus and Candida albicans. The obtained results could be perspective for applying in the pharmaceutical industry and for the conservation of food and cosmetic products.

Characterization and evolutionary analysis of Cucumber mosaic virus isolate infecting Salvia sclarea in India

Cucumber mosaic virus (CMV) is one of the most widespread viruses that infects a large number of cultivated crops worldwide and causes severe losses. Besides vegetables and ornamental crops, it is also spreading on medicinal and aromatic plants (MAPs) at an alarming rate. Natural occurrence of green mosaic, leaf curling, necrosis, and distortion were observed on the leaves of Salvia sclarea in the experimental field of CSIR-CIMAP, Lucknow, India. Mechanical transmission assay, morphological features, CP gene, and RNA3-based genomic characterization revealed the association of a new CMV isolate with the present disease. Virus is mechanically sap transmissible to the test plants. Transmission electron microscopy showed the presence of isodiametric particles of ~ 28 nm in diameter. Phylogenetic studies revealed that RNA3 (~ 2.2 kb) belongs to the subgroup IA of CMV. Multiple sequence alignment of amino acid sequences showed that MP possesses two unique changes in the RNA-binding domain and CP was found to be the conserved one with one change only. To the best of our knowledge, this is the first report of a CMV isolate infecting S. sclarea.

Phytomanagement of a metal(loid)-contaminated agricultural site using aromatic and medicinal plants to produce essential oils: analysis of the metal(loid) fate in the value chain

Phytomanagement uses plants and soil conditioners to create value on contaminated land while minimizing environmental risk. This work was carried out on a metal(loid)-contaminated site and aimed at assessing the suitability of Salvia sclarea L. (sage) and Coriandrum sativum L. (coriander) combined with an arbuscular mycorrhizal fungus (AMF) inoculant to immobilize metal(loid)s and produce essential oils (EO). The effect of the inoculant on the transfer of metal(loid)s (ML, i.e., Cd, Cu, Pb, Zn, As, Ni, and Sb) to plants and the ML soil mobility were investigated. The ML concentrations in EO from both plant species and the valorization options for the distillation residues (soil conditioner, animal fodder, and anaerobic digestion) were studied. Sage was a suitable candidate for this value chain because it presents an excluder phenotype and the residues of oil extraction could be used as a soil conditioner. The metal concentrations in the sage EO were similar to those obtained from plants cultivated on an uncontaminated soil. These results indicate the suitability of sage harvested on the contaminated soil according to the ML fate in the whole value chain. Like the EO of sage, ML concentrations in the coriander EO did not differ from those in the commercial EO that were obtained from plants grown on uncontaminated soil. However, the use of distillation residues of coriander was limited by their relatively elevated Cd concentrations. The use of a mycorrhizal inoculum did not decrease the Cd mobility in soil for the coriander.

In situ cultivation of aromatic plant species for the phytomanagement of an aged-trace element polluted soil: Plant biomass improvement options and techno-economic assessment of the essential oil production channel

Due to the presence of trace element (TE) in agricultural soils, wide areas are unproper for food production and the clean-up of soil is not a feasible option. Considering the potential remediation options, the use of aromatic plants producing a high quantity of biomass and developing high-added value sectors such as essential oil (EO) production could be valuable regarding one of the phytomanagement objectives, i.e. the restoration of an economic activity. The purpose of this study was hence to evaluate in situ the suitability of two aromatic crops, clary sage and coriander, for the phytomanagement of aged TE-polluted soils, taking into account plants' growth, development and biomass production, essential oil (EO) content and quality as well as a techno-economic feasibility analysis of the channel. In situ experiments have been carried out on two agricultural plots of 1.5 ha, a TE-polluted one (Pb: 394 ppm - Zn: 443 ppm - Cd: 7.2 ppm) and an unpolluted one (Pb: 22 ppm - Zn: 48 ppm - Cd: 0.4 ppm). Our findings have shown the ability of coriander and sage to grow similarly on both unpolluted and TE-polluted soil and to produce significant amounts of biomass. The pesticide residue and TE analyses have demonstrated that the EO only contained trace amounts of the contaminants, below or close to the limit of quantification of the method used and similar to marketed products. Mycorrhizal inoculation has also shown promising results by increasing the colonization rates of both aromatic plants, but did not result in higher biomass or EO amounts. Our study brings new evidence towards the potential of clary sage to be used for the phytomanagement of TE-polluted areas, given its perennial vegetation cover, tolerance to TE and obtained EO yields.

Clary Sage Cultivation and Mycorrhizal Inoculation Influence the Rhizosphere Fungal Community of an Aged Trace-Element Polluted Soil

Soil fungal communities play a central role in natural systems and agroecosystems. As such, they have attracted significant research interest. However, the fungal microbiota of aromatic plants, such as clary sage (Salvia sclarea L.), remain unexplored. This is especially the case in trace element (TE)-polluted conditions and within the framework of phytomanagement approaches. The presence of high concentrations of TEs in soils can negatively affect not only microbial diversity and community composition but also plant establishment and growth. Hence, the objective of this study is to investigate the soil fungal and arbuscular mycorrhizal fungi (AMF) community composition and their changes over time in TE-polluted soils in the vicinity of a former lead smelter and under the cultivation of clary sage. We used Illumina MiSeq amplicon sequencing to evaluate the effects of in situ clary sage cultivation over two successive years, combined or not with exogenous AMF inoculation, on the rhizospheric soil and root fungal communities. We obtained 1239 and 569 fungal amplicon sequence variants (ASV), respectively, in the rhizospheric soil and roots of S. sclarea under TE-polluted conditions. Remarkably, 69 AMF species were detected at our experimental site, belonging to 12 AMF genera. Furthermore, the inoculation treatment significantly shaped the fungal communities in soil and increased the number of AMF ASVs in clary sage roots. In addition, clary sage cultivation over successive years could be one of the explanatory parameters for the inter-annual variation in both fungal and AMF communities in the soil and root biotopes. Our data provide new insights on fungal and AMF communities in the rhizospheric soil and roots of an aromatic plant, clary sage, grown in TE-polluted agricultural soil.

Rapid Hormetic Responses of Photosystem II Photochemistry of Clary Sage to Cadmium Exposure

Five-day exposure of clary sage (Salvia sclarea L.) to 100 μM cadmium (Cd) in hydroponics was sufficient to increase Cd concentrations significantly in roots and aboveground parts and affect negatively whole plant levels of calcium (Ca) and magnesium (Mg), since Cd competes for Ca channels, while reduced Mg concentrations are associated with increased Cd tolerance. Total zinc (Zn), copper (Cu), and iron (Fe) uptake increased but their translocation to the aboveground parts decreased. Despite the substantial levels of Cd in leaves, without any observed defects on chloroplast ultrastructure, an enhanced photosystem II (PSII) efficiency was observed, with a higher fraction of absorbed light energy to be directed to photochemistry (ΦPSΙΙ). The concomitant increase in the photoprotective mechanism of non-photochemical quenching of photosynthesis (NPQ) resulted in an important decrease in the dissipated non-regulated energy (ΦNO), modifying the homeostasis of reactive oxygen species (ROS), through a decreased singlet oxygen (1O2) formation. A basal ROS level was detected in control plant leaves for optimal growth, while a low increased level of ROS under 5 days Cd exposure seemed to be beneficial for triggering defense responses, and a high level of ROS out of the boundaries (8 days Cd exposure), was harmful to plants. Thus, when clary sage was exposed to Cd for a short period, tolerance mechanisms were triggered. However, exposure to a combination of Cd and high light or to Cd alone (8 days) resulted in an inhibition of PSII functionality, indicating Cd toxicity. Thus, the rapid activation of PSII functionality at short time exposure and the inhibition at longer duration suggests a hormetic response and describes these effects in terms of "adaptive response" and "toxicity", respectively.

The Aromatic Plant Clary Sage Shaped Bacterial Communities in the Roots and in the Trace Element-Contaminated Soil More Than Mycorrhizal Inoculation - A Two-Year Monitoring Field Trial

To cope with soil contamination by trace elements (TE), phytomanagement has attracted much attention as being an eco-friendly and cost-effective green approach. In this context, aromatic plants could represent a good option not only to immobilize TE, but also to use their biomass to extract essential oils, resulting in high added-value products suitable for non-food valorization. However, the influence of aromatic plants cultivation on the bacterial community structure and functioning in the rhizosphere microbiota remains unknown. Thus, the present study aims at determining in TE-aged contaminated soil (Pb - 394 ppm, Zn - 443 ppm, and Cd - 7ppm, respectively, 11, 6, and 17 times higher than the ordinary amounts in regional agricultural soils) the effects of perennial clary sage (Salvia sclarea L.) cultivation, during two successive years of growth and inoculated with arbuscular mycorrhizal fungi, on rhizosphere bacterial diversity and community structure. Illumina MiSeq amplicon sequencing targeting bacterial 16S rRNA gene was used to assess bacterial diversity and community structure changes. Bioinformatic analysis of sequencing datasets resulted in 4691 and 2728 bacterial Amplicon Sequence Variants (ASVs) in soil and root biotopes, respectively. Our findings have shown that the cultivation of clary sage displayed a significant year-to-year effect, on both bacterial richness and community structures. We found that the abundance of plant-growth promoting rhizobacteria significantly increased in roots during the second growing season. However, we didn't observe any significant effect of mycorrhizal inoculation neither on bacterial diversity nor on community structure. Our study brings new evidence in TE-contaminated areas of the effect of a vegetation cover with clary sage cultivation on the microbial soil functioning.

Essential Oils

Salvia sclarea (SS) is characterized by its valuable essential oils (Eos) and potent biological activities. This study aimed at investigating the phytochemical composition of SS Eos collected in within the same week, from two different regions in Lebanon, Beirut (SS-Bt) and Taanayel (SS-Tl), utilizing GC-MS methods, and to explore their acute and subchronic antidiabetic potentials. Moreover, studying the phytochemical diversity of twenty SS Eos established on our work and literature descriptions in order to recognize the origin of the Lebanese active chemotype(s). The Eos have been obtained by hydro-distillation and identified via GC-MS analyses. Five chemotypes of SS Eos have been identified. The Lebanese Eos, SS-Bt and SS-Tl, studied here have shown evidence to belong to two different chemotypes 1 and 5, respectively. SS-Bt has shown to belong to chemotype 1, which is characterized by high linalool (LL) concentration (average 40.2%). On the other hand, SS-Tl has shown to belong to chemotype 5, which is characterized by high linalyl acetate (LA) concentration (average 50.4%). The acute and subchronic antidiabetic activities of these EOs have been monitored along with LL and LA, in order to find the most active chemotype. Chemotypes 1 (owned to high LL content), present at low altitude places of Lebanon and Poland, has shown significantly higher acute and subchronic antidiabetic activities than that of chemotype 5 (owned to high LA content). In conclusion, Salvia sclarea Eos have shown potential antidiabetic activities, and their Eos might be used in the future as a complementary or an alternative medicine in the management of diabetes and related complications.

Antimicrobial activity and mechanisms of Salvia sclarea essential oil

BACKGROUND

Nowadays, essential oils are recognized as safe substances and can be used as antibacterial additives. Salvia sclarea is one of the most important aromatic plants cultivated world-wide as a source of essential oils. In addition to being flavoring foods, Salvia sclarea essential oil can also act as antimicrobials and preservatives against food spoilage. Understanding more about the antibacterial performance and possible mechanism of Salvia sclarea essential oil will be helpful for its application in the future. But so far few related researches have been reported.

RESULTS

In our study, Salvia sclarea oil showed obvious antibacterial activity against all tested bacterial strains. Minimum inhibitory concentration (MIC) and minimum bactericide concentration (MBC) of seven pathogens were 0.05 and 0.1 % respectively. In addition, Salvia sclarea oil also exhibited a significant inhibitory effect on the growth of Escherichia coli (E. coli) in phosphate buffer saline (PBS) and meats. After treated with Salvia sclarea oil, Scanning Electron Microscope (SEM) images can clearly see the damage of cell membrane; the intracellular ATP concentrations of E. coli and S. aureus reduced 98.27 and 69.61 % respectively, compared to the control groups; the nuclear DNA content of E. coli and S. aureus was significantly reduced to 48.32 and 50.77 % respectively. In addition, there was massive leakage of cellular material when E. coli and S. aureus were exposed to Salvia sclarea oil.

CONCLUSIONS

Salvia sclarea essential oil damaged the cell membrane and changed the cell membrane permeability, leading to the release of some cytoplasm such as macromolecular substances, ATP and DNA. In general, the antimicrobial action of Salvia sclarea essential oil is not only attributable to a unique pathway, but also involves a series of events both on the cell surface and within the cytoplasm. Therefore, more experiments need to be done to fully understand the antimicrobial mechanism of Salvia sclarea essential oil.

Application of Heavy Metal Rich Tannery Sludge on Sustainable Growth, Yield and Metal Accumulation by Clarysage (Salvia sclarea L.)

A field experiment was conducted to evaluate the effective utilization of tannery sludge for cultivation of clarysage (Salvia sclarea) at CIMAP research farm, Lucknow, India during the year 2012-2013. Six doses (0, 20, 40, 60, 80, 100 tha(-1)) of processed tannery sludge were tested in randomised block design with four replications. Results revealed that maximum shoot, root, dry matter and oil yield were obtained with application of 80 tha(-1)of tannery sludge and these were 94, 113 and 61% higher respectively, over control. Accumulation of heavy metals (Cr, Ni, Fe, Pb) were relatively high in shoot portion of the plant than root. Among heavy metals, magnitude of chromium accumulation was higher than nickel, iron and lead in shoot as well as in root. Linalool, linalyl acetate and sclareol content in oil increased by 13,8 and 27% respectively over control, with tannery sludge application at 80 tha(-1). Heavy metals such as chromium, cadmium and lead content reduced in postharvest soil when compared to initial status. Results indicated that clarysage (Salvia sclarea) can be grown in soil amended with 80 tha(-1)sludge and this can be a suitable accumulator of heavy metals for phytoremediation of metal polluted soils.

Temporal transcriptome changes induced by methyl jasmonate in Salvia sclarea

Salvia sclarea is a traditional medicinal and aromatic plant that grows in Europe and produces various economically important compounds, including phenylpropanoid derivatives and terpenoids. Methyl jasmonate (MeJA) is commonly used to elicit plant stress responses. However, how MeJA enhances production of secondary metabolites in S. sclarea is not well understood. We performed a genome-wide analysis of temporal gene expression in S. sclarea leaves and roots. The transcriptome profiles 0, 10 and 26 h after MeJA treatment were analyzed by Illumina RNA-Seq. A total of 16,142 isogenes (average length 866bp; N50 1035bp) were obtained by de novo assembly of 35,757,567 raw sequencing reads. When these sequencing reads were mapped onto the assembled Unigenes, 3236, 2792 and 798 Unigenes were found to be expressed differentially between 0 and 10h, 0 and 26 h, and 10 and 26h, respectively. These included many secondary metabolite biosynthesis, stress and defense-related genes. A qRT-PCR analysis confirmed the expression profiles of selected differentially expressed genes (DEGs) revealed by RNA-Seq data, and also extended our analysis of differential gene expression to 73 h. Our investigations revealed temporal differences in the responses of S. sclarea to MeJA treatment. MeJA treatment induced the expression of a large number of genes involved in phenylpropanoid biosynthesis, especially between 0 and 10h, and 0 and 26 h. Additionally, many genes encoding transcription factors, cytochrome P450s, glycosyltransferases, methyltransferases and transporters were shown to respond to MeJA elicitation. DEGs related to structural molecule activity and cell death showed a significant temporal variation. A chromatographic analysis of metabolites at 26h, 73h and six days after MeJA treatment indicated that these transcriptomic changes precede MeJA-induced changes in secondary metabolite content. This study sheds light on the molecular mechanisms of MeJA elicitation and is helpful in understanding how exogenous MeJA treatment mediates extensive plant transcriptome reprogramming/remodeling. Our results can be utilized to characterize genes related to secondary metabolism and their regulation, and in breeding S. sclarea for desirable chemotypes.