Geographic and phenotypic variation in heartwood and essential-oil characters in natural populations of Santalum austrocaledonicum in Vanuatu

Comparative transcriptome profiling of high and low oil yielding Santalum album L

East Indian Sandalwood (Santalum album L.) is highly valued for its heartwood and its oil. There have been no efforts to comparative study of high and low oil yielding genetically identical sandalwood trees grown in similar climatic condition. Thus we intend to study a genome wide transcriptome analysis to identify the corresponding genes involved in high oil biosynthesis in S. album. In this study, 15 years old S. album (SaSHc and SaSLc) genotypes were targeted for analysis to understand the contribution of genetic background on high oil biosynthesis in S. album. A total of 28,959187 and 25,598869 raw PE reads were generated by the Illumina sequencing. 2.12 million and 1.811 million coding sequences were obtained in respective accessions. Based on the GO terms, functional classification of the CDS 21262, & 18113 were assigned into 26 functional groups of three GO categories; (4,168; 3,641) for biological process (5,758;4,971) cellular component and (5,108;4,441) for molecular functions. Total 41,900 and 36,571 genes were functionally annotated and KEGG pathways of the DEGs resulted 213 metabolic pathways. In this, 14 pathways were involved in secondary metabolites biosynthesis pathway in S. album. Among 237 cytochrome families, nine groups of cytochromes were participated in high oil biosynthesis. 16,665 differentially expressed genes were commonly detected in both the accessions (SaHc and SaSLc). The results showed that 784 genes were upregulated and 339 genes were downregulated in SaHc whilst 635 upregulated 299 downregulated in SaSLc S. album. RNA-Seq results were further validated by quantitative RT-PCR. Maximum Blast hits were found to be against Vitis vinifera. From this study, we have identified additional number of cytochrome family in high oil yielding sandalwood accessions (SaHc). The accessibility of a RNA-Seq for high oil yielding sandalwood accessions will have broader associations for the conservation and selection of superior elite samples/populations for further genetic improvement program.

The Assessment of Quality of Products Called Sandalwood Oil Based on the Information Provided by Manufacturer of the Oil on Polish, German, and English Websites

BACKGROUND

Sandalwood oil is one of the most valuable raw materials worldwide. As a highly valued product, it has its own regulations based on the ISO 3518 standard, which clearly informs producers, distributors, and consumers of the requirements to be met. The aim of this study was to assess the quality of products called sandalwood oil based on the information provided by the manufacturer of the oils on Polish, German, and English websites.

METHODS

A Google search was utilized to collect data on sandalwood oil offered by producers and distributors in Polish and foreign markets. Information from 50 websites in each of the aforementioned languages, including the description of sandalwood oil properties on websites, method for using it, safety limitations, and presence of a product description consistent with the INCI recommendations, was gathered using Microsoft Excel software and was analyzed. The information that enabled us to estimate the quality of the oils was the botanical name of the oil-bearing plant and the price. Good-quality oils were considered to be oils with the botanical name Santalum album in the description and with a price not considerably less than the price of white sandalwood oils sold by reliable distributors who control the quality of the oils by chromatography. Ultimately, the lower price limit for one milliliter of the oil was established as PLN 21. Results and Conclusions. Good-quality sandalwood oils derived from the Santalum album plant at a price equal to or greater than the chromatographically tested items amounted to a negligible percentage of products sold online. Without knowing the botanical name of the essential oil plant and the price range of unadulterated sandalwood oil, the likelihood of buying a reliable product is low on all of the analyzed websites, with the lowest probability being observed on the Polish websites.

From ethnobotany to mainstream agriculture: socially modified Cinderella species capturing 'trade-ons' for 'land maxing'

Over the last 25 years, the process of domesticating culturally-important, highly-nutritious, indigenous food-tree species. Integrating these over-looked 'Cinderella' species into conventional farming systems as new crops is playing a critical role in raising the productivity of staple food crops and improving the livelihoods of poor smallholder farmers. This experience has important policy implications for the sustainability of tropical/sub-tropical agriculture, the rural economy and the global environment. A participatory domestication process has been implemented in local communities using appropriate horticultural technologies to characterize genetic variation in non-timber forest products and produce putative cultivars by the vegetative propagation of elite trees in rural resource centers. When integrated into mainstream agriculture, these new crops diversify farmers' fields and generate income. Together, these outcomes address land degradation and social deprivation-two of the main constraints to staple food production-through beneficial effects on soil fertility, agroecosystem functions, community livelihoods, local trade and employment. Thus, the cultivation of these 'socially modified crops' offers a new strategy for the sustainable intensification of tropical agriculture based on the maximization of total factor productivity with minimal environmental and social trade-offs.

The in vitro antimicrobial evaluation of commercially essential oils and their combinations against acne

OBJECTIVE

The study investigated the efficacy of commercial essential oil combinations against the two pathogens responsible for acne with the aim to identify synergy and favourable oils to possibly use in a blend.

MATERIALS AND METHODS

Antimicrobial activity was assessed using the minimum inhibitory concentration (MIC) assay against Staphylococcus epidermidis (ATCC 2223) and Propionibacterium acnes (ATCC 11827), and the fractional inhibitory concentration index (ΣFIC) was calculated. Combinations displaying synergistic interactions were further investigated at varied ratios and the results plotted on isobolograms.

RESULTS

From the 408 combinations investigated, 167 combinations were identified as displaying noteworthy antimicrobial activity (MIC value ≤1.00 mg mL-1 ). Thirteen synergistic interactions were observed against S. epidermidis, and three synergistic combinations were observed against P. acnes. It was found that not one of the synergistic interactions identified were based on the combinations recommended in the layman's aroma-therapeutic literature. Synergy was evident rather from leads based on antimicrobial activity from previous studies, thus emphasizing the importance of scientific validation. Leptospermum scoparium J.R.Forst. and G.Forst (manuka) was the essential oil mostly involved in synergistic interactions (four) against S. epidermidis. Cananga odorata (Lam.) Hook.f. and Thomson (ylang ylang) essential oil was also frequently involved in synergy where synergistic interactions could be observed against both pathogens. The combination with the lowest MIC value against both acne pathogens was Vetiveria zizanioides Stapf (vetiver) with Cinnamomum verum J.Presl (cinnamon bark) (MIC values 0.19-0.25 mg mL-1 ). Pogostemon patchouli Benth. (patchouli), V. zizanioides, C. verum and Santalum spp. (sandalwood) could be identified as the oils that contributed the most noteworthy antimicrobial activity towards the combinations. The different chemotypes of the essential oils used in the combinations predominantly resulted in similar antimicrobial activity.

CONCLUSIONS

The investigated essential oil combinations resulted in at least 50% of the combinations displaying noteworthy antimicrobial activity. Most of the synergistic interactions do not necessarily correspond to the recommended layman's aroma-therapeutic literature, which highlights a need for scientific validation of essential oil antimicrobial activity. No antagonism was observed.

Sesquiterpene Variation in West Australian Sandalwood (Santalum spicatum)

West Australian sandalwood (Santalum spicatum) has long been exploited for its fragrant, sesquiterpene-rich heartwood; however sandalwood fragrance qualities vary substantially, which is of interest to the sandalwood industry. We investigated metabolite profiles of trees from the arid northern and southeastern and semi-arid southwestern regions of West Australia for patterns in composition and co-occurrence of sesquiterpenes. Total sesquiterpene content was similar across the entire sample collection; however sesquiterpene composition was highly variable. Northern populations contained the highest levels of desirable fragrance compounds, α- and β-santalol, as did individuals from the southwest. Southeastern populations were higher in E,E-farnesol, an undesired allergenic constituent, and low in santalols. These trees generally also contained higher levels of α-bisabolol. E,E-farnesol co-occurred with dendrolasin. Contrasting α-santalol and E,E-farnesol chemotypes revealed potential for future genetic tree improvement. Although chemical variation was evident both within and among regions, variation was generally lower within regions. Our results showed distinct patterns in chemical diversity of S. spicatum across its natural distribution, consistent with earlier investigations into sandalwood population genetics. These results are relevant for plantation tree improvement and conservation efforts.

Plant Volatilome in Greece: a Review on the Properties, Prospects, and Chemogeography

Knowing plant volatile chemodiversity and its distribution is essential in order to study biological processes, to estimate the plants' value in use, and to establish sustainable exploitation practices. Yet, attempts to collect and assess data on scent diversity and properties in well-defined geographical areas are rare. Here, we developed a geo-referenced database of the plant volatilome in Greece by consolidating the results included in 116 research articles published in the last 25 years. The data set compiled includes 999 volatile organic compounds distributed into 178 plant taxa, 59 genera, and 19 families. Distillation is the acquisition method almost exclusively used, whereas headspace techniques that would allow the study of subtle ecological processes are generally lacking. Sesquiterpenes show the greatest richness of compounds, followed by monoterpenes and aliphatics. We assess the volatility of the compounds using the normal boiling point (nBP) as its reverse indicator, and we present the volatility spectra of the blends of the genera studied. Mean nBPs vary among genera, with maximal differences as wide as 118.4°. Finally, we feature basic chemodiversity maps for three aromatic plants, and discuss their importance and prospects as a special case of natural resources maps.

Sandalwood: basic biology, tissue culture, and genetic transformation

Sustainable resource preservation of Santalum species that yield commercially important forest products is needed. This review provides an understanding of their basic biology, propagation, hemi-parasitic nature, reproductive biology, and biotechnology. Many species of the genus Santalum (Santalaceae) have been exploited unremittingly for centuries, resulting in the extinction of one and the threatened status of three other species. This reduction in biodiversity of sandalwood has resulted from the commercial exploitation of its oil-rich fragrant heartwood. In a bid to conserve the remaining germplasm, biotechnology provides a feasible, and effective, means of propagating members of this genus. This review provides a detailed understanding of the biological mechanisms underlying the success or failure of traditional propagation, including a synopsis of the process of hemi-parasitism in S. album, and of the suitability of host plants to sustain the growth of seedlings and plants under forestry production. For the mass production of economically important metabolites, and to improve uniformity of essential oils, the use of clonal material of similar genetic background for cultivation is important. This review summarizes traditional methods of sandalwood production with complementary and more advanced in vitro technologies to provide a basis for researchers, conservationists and industry to implement sustainable programs of research and development for this revered genus.

Functional Characterization of Novel Sesquiterpene Synthases from Indian Sandalwood, Santalum album

Indian Sandalwood, Santalum album L. is highly valued for its fragrant heartwood oil and is dominated by a blend of sesquiterpenes. Sesquiterpenes are formed through cyclization of farnesyl diphosphate (FPP), catalyzed by metal dependent terpene cyclases. This report describes the cloning and functional characterization of five genes, which encode two sesquisabinene synthases (SaSQS1, SaSQS2), bisabolene synthase (SaBS), santalene synthase (SaSS) and farnesyl diphosphate synthase (SaFDS) using the transcriptome sequencing of S. album. Using Illumina next generation sequencing, 33.32 million high quality raw reads were generated, which were assembled into 84,094 unigenes with an average length of 494.17 bp. Based on the transcriptome sequencing, five sesquiterpene synthases SaFDS, SaSQS1, SaSQS2, SaBS and SaSS involved in the biosynthesis of FPP, sesquisabinene, β-bisabolene and santalenes, respectively, were cloned and functionally characterized. Novel sesquiterpene synthases (SaSQS1 and SaSQS2) were characterized as isoforms of sesquisabinene synthase with varying kinetic parameters and expression levels. Furthermore, the feasibility of microbial production of sesquisabinene from both the unigenes, SaSQS1 and SaSQS2 in non-optimized bacterial cell for the preparative scale production of sesquisabinene has been demonstrated. These results may pave the way for in vivo production of sandalwood sesquiterpenes in genetically tractable heterologous systems.

The transcriptome of sesquiterpenoid biosynthesis in heartwood xylem of Western Australian sandalwood (Santalum spicatum)

The fragrant heartwood oil of West Australian sandalwood (Santalum spicatum) contains a mixture of sesquiterpene olefins and alcohols, including variable levels of the valuable sesquiterpene alcohols, α- and β-santalol, and often high levels of E,E-farnesol. Transcriptome analysis revealed sequences for a nearly complete set of genes of the sesquiterpenoid biosynthetic pathway in this commercially valuable sandalwood species. Transcriptome sequences were produced from heartwood xylem tissue of a farnesol-rich individual tree. From the assembly of 12,537 contigs, seven different terpene synthases (TPSs), several cytochromes P450, and allylic phosphatases were identified, as well as transcripts of the mevalonic acid and methylerythritol phosphate pathways. Five of the S. spicatum TPS sequences were previously unknown. The full-length cDNA of SspiTPS4 was cloned and the enzyme functionally characterized as a multi-product sesquisabinene B synthase, which complements previous characterization of santalene and bisabolol synthases in S. spicatum. While SspiTPS4 and previously cloned sandalwood TPSs do not explain the prevalence of E,E-farnesol in S. spicatum, the genes identified in this and previous work can form a basis for future studies on natural variation of sandalwood terpenoid oil profiles.

Hawaiian Sandalwood: Oil Composition of Santalum paniculatum and Comparison with Other Sandal Species

Four commercial qualities of Hawaiian sandalwood oil produced from wood of Santalum paniculatum originating from the island of Hawaii (“The Big Island”) were analyzed using GC and GC-MS. Main constituents of the oils were ( Z)-α-santalol (34.5–40.4%) and ( Z)-β-santalol (11.0–16.2%). An odor evaluation of the oils was carried out against East Indian sandalwood oil. In addition, the chemical composition of Hawaiian sandalwood oil was compared with four different Santalum species originating from East India, New Caledonia, Eastern Polynesia and Australia, respectively.

Biosynthesis of Sandalwood Oil: Santalum album CYP76F cytochromes P450 produce santalols and bergamotol

Sandalwood oil is one of the world’s most highly prized essential oils, appearing in many high-end perfumes and fragrances. Extracted from the mature heartwood of several Santalum species, sandalwood oil is comprised mainly of sesquiterpene olefins and alcohols. Four sesquiterpenols, α-, β-, and epi-β-santalol and α-exo-bergamotol, make up approximately 90% of the oil of Santalum album. These compounds are the hydroxylated analogues of α-, β-, and epi-β-santalene and α-exo-bergamotene. By mining a transcriptome database of S. album for candidate cytochrome P450 genes, we cloned and characterized cDNAs encoding a small family of ten cytochrome P450-dependent monooxygenases annotated as SaCYP76F37v1, SaCYP76F37v2, SaCYP76F38v1, SaCYP76F38v2, SaCYP76F39v1, SaCYP76F39v2, SaCYP76F40, SaCYP76F41, SaCYP76F42, and SaCYP76F43. Nine of these genes were functionally characterized using in vitro assays and yeast in vivo assays to encode santalene/bergamotene oxidases and bergamotene oxidases. These results provide a foundation for production of sandalwood oil for the fragrance industry by means of metabolic engineering, as demonstrated with proof-of-concept formation of santalols and bergamotol in engineered yeast cells, simultaneously addressing conservation challenges by reducing pressure on supply of sandalwood from native forests.

Chemical and genetic differentiation of two Mediterranean subspecies of Teucrium scorodonia L

Chemical and genetic diversity of Teucrium scorodonia L. subsp. scorodonia from Corsica and T. scorodonia L. subsp. baeticum from western Algeria were investigated. Diversity within and among the two populations of subspecies was assessed according to the chemical composition of their essential oils, and genetic diversity was evaluated using three polymorphic genetic markers. Chemical analysis was performed using a combination of capillary GC-RI and GC/MS after fractionation using column chromatography. Genetic structures were mapped using two chloroplast markers (RPL32-TRNL and TRNL-F) and ribosomal nuclear markers (ITS region). The statistical analysis showed that the two subspecies were clearly distinguished by these chemical and genetic markers. The chemical composition of oil differed qualitatively and quantitatively between the subspecies. Corsican oil samples contained germacrene B (4.2-8.8%) and γ-elemene (2.6-5.7%), which were not detected in Algerian oil samples. The oils of the scorodonia and baeticum subspecies were dominated by sesquiterpene hydrocarbon compounds (75.6-82.9% and 69.6-79.4%, respectively), but they differed in oxygenated sesquiterpene content (3.1-8.9% and 8.4-20.3%, respectively). Neighbor-joining trees constructed from chloroplast DNA and ITS region sequences showed the existence of two groups associated with taxonomic and chemical characteristics. One group consisted of T. scorodonia subsp. scorodonia and the other of T. scorodonia subsp. baeticum, indicating that variation in the essential oil composition of T. scorodonia subspecies depends more on genetic background than environmental characteristics.

Sandalwood fragrance biosynthesis involves sesquiterpene synthases of both the terpene synthase (TPS)-a and TPS-b subfamilies, including santalene synthases

Sandalwood oil is one of the worlds most highly prized fragrances. To identify the genes and encoded enzymes responsible for santalene biosynthesis, we cloned and characterized three orthologous terpene synthase (TPS) genes SaSSy, SauSSy, and SspiSSy from three divergent sandalwood species; Santalum album, S. austrocaledonicum, and S. spicatum, respectively. The encoded enzymes catalyze the formation of α-, β-, epi-β-santalene, and α-exo-bergamotene from (E,E)-farnesyl diphosphate (E,E-FPP). Recombinant SaSSy was additionally tested with (Z,Z)-farnesyl diphosphate (Z,Z-FPP) and remarkably, found to produce a mixture of α-endo-bergamotene, α-santalene, (Z)-β-farnesene, epi-β-santalene, and β-santalene. Additional cDNAs that encode bisabolene/bisabolol synthases were also cloned and functionally characterized from these three species. Both the santalene synthases and the bisabolene/bisabolol synthases reside in the TPS-b phylogenetic clade, which is more commonly associated with angiosperm monoterpene synthases. An orthologous set of TPS-a synthases responsible for formation of macrocyclic and bicyclic sesquiterpenes were characterized. Strict functionality and limited sequence divergence in the santalene and bisabolene synthases are in contrast to the TPS-a synthases, suggesting these compounds have played a significant role in the evolution of the Santalum genus.