Secretion mechanisms of volatile organic compounds in specialized cells of aromatic plants

The present review focuses on cells secreting volatile odorant compounds. This cell type is found in a wide variety of plants, grouped under the term aromatic plants. Such secreting cells are very diverse in morphology, from highly specialized trichomes to nonspecialized cells, including the secretory epidermal cells of petals and osmophores. In these various types of cell, the biosynthetic pathways of three main groups of volatile organic compounds are recognized: isoprenoids, fatty acid derivatives and aromatic compounds. The precise cellular localization of these pathways has not yet been elucidated in all cases, though many of the enzymes involved have already been cloned. These have been found to be frequently located in plastids but also in endoplasmic reticulum or even cytosol. Two alternative mechanisms of secretion termed granulocrine and eccrine have been postulated to exist. Recent studies support the fact that both mechanisms could exist for different compounds and different plants. This review will discuss also the route by which secreted molecules make their way through the cell wall and cuticle

Optimized Antibacterial Effects in a Designed Mixture of Essential Oils of Myrtus communis, Artemisia herba-alba and Thymus serpyllum for Wide Range of Applications

Nowadays, the combination of molecules influences their biological effects, and interesting outcomes can be obtained from different component interactions. Using a mixture design method, this research seeks to simulate the efficacy of essential oil combinations against various bacteria and forecast the ideal combination. The chemical compositions of Myrtus communis, Artemisia herba-alba and Thymus serpyllum essential oils were analyzed using CG/MS. Then, the combined antibacterial effects were evaluated by testing mixture design formulations using the microdilution bioassay. The main compounds detected for M. communis essential oil were myrtenyl acetate (33.67%), linalool (19.77%) and 1,8-cineole (10.65%). A. herba-alba had piperitone as a chemotype, representing 85%. By contrast, the T. serpyllum oil contained thymol (17.29%), γ-terpinene (18.31%) and p-cymene (36.15%). The antibacterial effect of the essential oils studied, and the optimum mixtures obtained were target strain-dependent. T. serpyllum alone ensured the optimal inhibition against S. aureus and E. coli, while a ternary mixture consisting of 17.1%, 39.6% and 43.1% of M. communis, A. herba-alba and T. serpyllum respectively, was associated with optimal inhibitory activity against B. subtilis. The outcome of this research supports the idea of the boosting effect of essential oil combinations toward better activities, giving better understanding of the usefulness of mixture designs for food, cosmetics, and pharmaceutical applications

Optimized Antibacterial Effects in a Designed Mixture of Essential Oils of Myrtus communis, Artemisia herba-alba and Thymus serpyllum for Wide Range of Applications

Nowadays, the combination of molecules influences their biological effects, and interesting outcomes can be obtained from different component interactions. Using a mixture design method, this research seeks to simulate the efficacy of essential oil combinations against various bacteria and forecast the ideal combination. The chemical compositions of Myrtus communis, Artemisia herba-alba and Thymus serpyllum essential oils were analyzed using CG/MS. Then, the combined antibacterial effects were evaluated by testing mixture design formulations using the microdilution bioassay. The main compounds detected for M. communis essential oil were myrtenyl acetate (33.67%), linalool (19.77%) and 1,8-cineole (10.65%). A. herba-alba had piperitone as a chemotype, representing 85%. By contrast, the T. serpyllum oil contained thymol (17.29%), gamma-terpinene (18.31%) and p-cymene (36.15%). The antibacterial effect of the essential oils studied, and the optimum mixtures obtained were target strain-dependent. T. serpyllum alone ensured the optimal inhibition against S. aureus and E. coli, while a ternary mixture consisting of 17.1%, 39.6% and 43.1% of M. communis, A. herba-alba and T. serpyllum respectively, was associated with optimal inhibitory activity against B. subtilis. The outcome of this research supports the idea of the boosting effect of essential oil combinations toward better activities, giving better understanding of the usefulness of mixture designs for food, cosmetics, and pharmaceutical applications.Peer reviewe

Optimized Antibacterial Effects in a Designed Mixture of Essential Oils of Myrtus communis, Artemisia herba-alba and Thymus serpyllum for Wide Range of Applications

Nowadays, the combination of molecules influences their biological effects, and interesting outcomes can be obtained from different component interactions. Using a mixture design method, this research seeks to simulate the efficacy of essential oil combinations against various bacteria and forecast the ideal combination. The chemical compositions of Myrtus communis, Artemisia herba-alba and Thymus serpyllum essential oils were analyzed using CG/MS. Then, the combined antibacterial effects were evaluated by testing mixture design formulations using the microdilution bioassay. The main compounds detected for M. communis essential oil were myrtenyl acetate (33.67%), linalool (19.77%) and 1,8-cineole (10.65%). A. herba-alba had piperitone as a chemotype, representing 85%. By contrast, the T. serpyllum oil contained thymol (17.29%), γ-terpinene (18.31%) and p-cymene (36.15%). The antibacterial effect of the essential oils studied, and the optimum mixtures obtained were target strain-dependent. T. serpyllum alone ensured the optimal inhibition against S. aureus and E. coli, while a ternary mixture consisting of 17.1%, 39.6% and 43.1% of M. communis, A. herba-alba and T. serpyllum respectively, was associated with optimal inhibitory activity against B. subtilis. The outcome of this research supports the idea of the boosting effect of essential oil combinations toward better activities, giving better understanding of the usefulness of mixture designs for food, cosmetics, and pharmaceutical applications

Tinkering with the C-Function: A Molecular Frame for the Selection of Double Flowers in Cultivated Roses

International audienc

Biosynthèse et sécrétion du parfum chez Rosa x hybrida L.

La rose présente un intérêt économique très important tant pour son utilisation pour la parfumerie et les cosmétiques que pour son utilisation en horticulture. La rose moderne résulte d'un long processus de sélection au cours duquel les variétés cultivées pour la fleur coupée, notamment, ont perdu leur parfum. Le parfum des roses est un mélange complexe de composés volatils, parmi lesquels les monoterpènes représentent une proportion importante. Aujourd'hui, le parfum est devenu un caractère de choix pour les créateurs de nouvelles variétés. Dans un premier temps, nous nous sommes attaché à caractériser le pétale de rose en tant qu'organe producteur et sécréteur de composés volatils. Nous avons pu montrer que les deux épidermes du pétale produisent et émettent des composés et renferment une enzyme responsable de leur synthèse. Des structures caractéristiques de la synthèse des monoterpènes ont été mises en évidence. Une étude comparative des pétales de roses parfumées et inodores a été réalisée parallèlement. Dans un deuxième temps, deux gènes impliqués dans la biosynthèse des monoterpènes ont été isolés : RhDXR et RhGPPS. L'activité enzymatique de la protéine RhGPPS n'a pas pu être mise en évidence in vitro. L'expression de ce gène est constitutive et non spécifique des roses produisant des monoterpènes. Le gène RhDXR code pour une protéine fonctionnelle. Son expression a été étudiée par RT-PCR semi-quantitative et sa localisation subcellulaire a été précisée par des fusions avec la GFP. Des tabacs transgéniques surexprimant RhDXR sont en cours d'analyse, dans le but d'évaluer la capacité des plantes à augmenter leur production en composés volatilsRoses are the most economically important horticultural species because of their use in fragrance industry and in horticulture. Modern roses are the results of a long selection process lying on the vase life, the pest and disease resistance, the shape and the colour of the flower. Fragrance of roses for the cut flower market was not selected during this process. But nowdays, fragrance is of great interest for the breeders. Perfume of roses is a complex mixture of volatile compounds, mainly monoterpenes. The aim of my work was to characterize the petal of roses as a secretory organ and to isolate and characterize two genes involved in the biosynthetic pathway of monoterpenes. For this purpose, we studied the petal at the ultrastructural level. Both epidermis of the petal are able to synthezize and emit volatile compounds. We identified some structural features putatively involved in the biosynthesis of monoterpenes. A comparative study was made between scented and non-scented varieties but no major differences were observed. Two enzymes involved in the biosynthetic pathway of monoterpenes were studied : RhDXR, involved in IPP biosynthesis and the homodimeric form of RhGPPS, involved in the production of GPP, precursor of monoterpenes. In an in vitro assay, no enzymatic activity was detected for the recombiant RhGPPS. Expression of the corresponding gene was studied by RT-PCR. Its expression is constitutive and not related to biosynthesis of monoterpenes in different rose varieties. RhDXR was characterized as a functional enzyme. The expression of RhDXR was studied by semi-quantitative RT-PCR. By fusions with GFP, we showed that the protein is targeted to the plastids of rose petals. The effect of the overexpression of this gene in transgenic tobaccos is currently under study, with the aim to evaluate the ability of plants to produce more volatiles compounds.ST ETIENNE-BU Sciences (422182103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Omics in Chemical Ecology

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Etude de deux gènes impliqués dans la biosynthèse du parfum chez le genre Rosa L. (Rosaceae)

Peu d enzymes de synthèse de composés odorants sont connues chez le genre Rosa. Ce travail de thèse a permis l identification de quelques-unes de ces protéines grâce à la technologie des puces à ADN, à l analyse de l expression des gènes par RT-PCR quantitative en temps réel (qPCR) et à l analyse des parfums par chromatographie en phase gazeuse (CPG). Une puce confrontant les ADNc d une rose parfumée à ceux d une rose non parfumée a permis de corréler l expression d un gène, codant pour une Nudix hydrolase, très fortement exprimé dans la rose parfumée, avec la présence des monoterpènes dans le parfum de nombreux cultivars de rosiers. La caractérisation d un rosier dont l expression de ce gène est fortement réduite par ARN interférants, a permis de confirmer le rôle de celui-ci dans la synthèse des monoterpènes. La phénylacétaldéhyde synthase (PAAS) est une autre enzyme participant à la synthèse du parfum. Trois allèles de cette protéine ont précédemment été mis en évidence. Les résultats de qPCR et de CPG dans une population hybride ont permis de montrer que l allèle a1 est le seul à pouvoir induire la synthèse et l émission de 2-phényléthanol. Les activités respectives des différentes isoformes ont été testées in vitro chez la levure et in planta dans des feuilles de tabac et des cals de rosier : ces expériences montrent que les trois isoformes ont des activités comparables. L absence de synthèse de 2-phényméthanol chez les plantes présentant les isoformes a2 et a3 réside donc dans la très faible expression de leurs allèles, induisant probablement une faible concentration de l isoforme dans les cellulesVery few enzymes responsible for the biosynthesis of scent compounds in the genus Rosa are known so far. This PhD thesis aims to identify some of these proteins with DNA microarray technology, gene expression analysis by real-time quantitative PCR (qPCR) and scent analysis by gas chromatography (GC). An array comparing cDNA from a scented rose to those of a non-scented one, showed a correlation between expression of a yet-unknown gene, encoding a Nudix hydrolase, highly expressed in the scented rose, and the presence of monoterpenes in the scent of many rose cultivars. Characterization of a rose cultivar, in which expression of this gene has been decreased by RNA interference, confirmed its role in monoterpene synthesis. The phenylacetaldehyde synthase (PAAS) is another enzyme implicated in scent biosynthesis. Three alleles of this protein had been previously described. qPCR and GC experiments in a hybrid population showed that the a1 allele is the only one able to induce 2-phenylethanol biosynthesis. The respective activities of the different isoforms were tested in vitro in yeast, and in planta in tobacco leaves and rose calli: these experiments showed that the three isoforms have comparable activities. The lack of 2-phenylethanol production in plants having a2 and a3 isoforms is thus due to the very low expression of their respective alleles, probably inducing very low isoform concentration in cellsST ETIENNE-Bib. électronique (422189901) / SudocSudocFranceF

Les Omiques en écologie chimique

International audienc

Model Plants and Functional Genomic Approaches Applied to the Characterization ofGenes Involved in Floral Scent Biosynthesis

International audienceFlower scents have been subjected to extensive chemical characterization for many years, providing detailed analyses of the complex mixture of volatiles emitted by flowers. However, the past ten years have seen a rapid acceleration of progress in flower scent research, with the characterization of numerous genes involved in scent biosynthesis. This review focuses on the evolution of flower scent research, from the early biochemical to the present genomic approaches, illustrating how the use of different plant models, combined with functional genomic approaches, contributed to the present knowledge in this field