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

Very 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 cellsPeu 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 cellule

Study of two genes implicated in scent biosynthesis in the genus 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 cell

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

A new and endemic species of Drosera (Droseraceae) from Madagascar

Background and aims – This study is part of an ongoing revision of the world Drosera species. During herbarium revisions of Drosera from Madagascar, a new species was identified and is here described.Methods – The species’ morphology is described based on herbarium studies and observation of living plants in situ, and ecological notes from field observations are provided. The species is compared and contextualized within the current subgeneric classification of Drosera.Key results – The new species, Drosera arachnoides, is recognized as most closely related to another Malagasy-endemic, D. humbertii, from which it is morphologically and ecologically distinct. The new species is placed within D. subg. Drosera sect. Ptycnostigma. Based on the restricted occurrence, the species is assessed as Vulnerable, following IUCN categories and criteria. A key to the Drosera species from Madagascar is provided.Conclusion – Drosera arachnoides is the second endemic Drosera species in Madagascar and raises the total number of species on the island to six

Combinaisons nouvelles requises dans la seconde édition de Flora Gallica

International audience73 combinaisons et noms nouveaux sont proposés en vue de changements taxonomiques dans la seconde édition de Flora Gallic

Biosynthesis of 2-Phenylethanol in Rose Petals Is Linked to the Expression of One Allele of <i>RhPAAS</i>

International audienceFloral scent is one of the most important characters in horticultural plants. Roses (Rosa spp.) have been cultivated for their scent since antiquity. However, probably by selecting for cultivars with long vase life, breeders have lost the fragrant character in many modern roses, especially the ones bred for the cut flower market. The genetic inheritance of scent characters has remained elusive so far. In-depth knowledge of this quantitative trait is thus very much needed to breed more fragrant commercial cultivars. Furthermore, rose hybrids harbor a composite genomic structure, which complexifies quantitative trait studies. To understand rose scent inheritance, we characterized a segregating population from two diploid cultivars, Rosa × hybrida cv H190 and Rosa wichurana, which have contrasting scent profiles. Several quantitative trait loci for the major volatile compounds in this progeny were identified. One among these loci contributing to the production of 2-phenylethanol, responsible for the characteristic odor of rose, was found to be colocalized with a candidate gene belonging to the 2-phenylethanol biosynthesis pathway: the PHENYLACETALDEHYDE SYNTHASE gene RhPAAS. An in-depth allele-specific expression analysis in the progeny demonstrated that only one allele was highly expressed and was responsible for the production of 2-phenylethanol. Unexpectedly, its expression was found to start early during flower development, before the production of the volatile 2-phenylethanol, leading to the accumulation of glycosylated compounds in petals.Analyse des composés du parfum dans une population en ségrégation qui montre que la synthèse du&nbsp;2-phenylethanol est liée à l'expression d'un allèle deu gène de la&nbsp;phenylacetaldehyde synthase dans les pétale

Transcriptome database resource and gene expression atlas for the rose

International audienceBackground: For centuries roses have been selected based on a number of traits. Little information exists on the genetic and molecular basis that contributes to these traits, mainly because information on expressed genes for this economically important ornamental plant is scarce. Results: Here, we used a combination of Illumina and 454 sequencing technologies to generate information on Rosa sp. transcripts using RNA from various tissues and in response to biotic and abiotic stresses. A total of 80714 transcript clusters were identified and 76611 peptides have been predicted among which 20997 have been clustered into 13900 protein families. BLASTp hits in closely related Rosaceae species revealed that about half of the predicted peptides in the strawberry and peach genomes have orthologs in Rosa dataset. Digital expression was obtained using RNA samples from organs at different development stages and under different stress conditions. qPCR validated the digital expression data for a selection of 23 genes with high or low expression levels. Comparative gene expression analyses between the different tissues and organs allowed the identification of clusters that are highly enriched in given tissues or under particular conditions, demonstrating the usefulness of the digital gene expression analysis. A web interface ROSAseq was created that allows data interrogation by BLAST, subsequent analysis of DNA clusters and access to thorough transcript annotation including best BLAST matches on Fragaria vesca, Prunus persica and Arabidopsis. The rose peptides dataset was used to create the ROSAcyc resource pathway database that allows access to the putative genes and enzymatic pathways. Conclusions: The study provides useful information on Rosa expressed genes, with thorough annotation and an overview of expression patterns for transcripts with good accuracy

Biosynthesis of monoterpene scent compounds in roses

International audienceStop to smell the roses Some roses smell beautiful, yet others only look beautiful. Magnard et al. leveraged this distinction to study the biosynthesis of geraniol, a monoterpene alcohol in rose scent (see the Perspective by Tholl and Gershenzon). Enzymes known for geraniol synthesis in other plants, such as basil, did not seem to provide that function for roses. Instead, a diphosphohydrolase, which functions in the cytoplasm of cells in rose petals, generates the geraniol emitted by fragrant roses. Identification of the enzyme and its gene enables marker-assisted breeding to put the perfume back into beauty. Science , this issue p. 81 ; see also p. 2

Biosynthesis of monoterpene scent compounds in roses

The scent of roses (Rosa x hybrida) is composed of hundreds of volatile molecules.Monoterpenes represent up to 70% percent of the scent content in some cultivars, such asthe Papa Meilland rose. Monoterpene biosynthesis in plants relies on plastid-localizedterpene synthases. Combining transcriptomic and genetic approaches, we show thatthe Nudix hydrolase RhNUDX1, localized in the cytoplasm, is part of a pathway for thebiosynthesis of free monoterpene alcohols that contribute to fragrance in roses. TheRhNUDX1 protein shows geranyl diphosphate diphosphohydrolase activity in vitro andsupports geraniol biosynthesis in planta