Label-free shotgun proteomics and metabolite analysis reveal a significant metabolic shift during citrus fruit development.

Label-free LC-MS/MS-based shot-gun proteomics was used to quantify the differential protein synthesis and metabolite profiling in order to assess metabolic changes during the development of citrus fruits. Our results suggested the occurrence of a metabolic change during citrus fruit maturation, where the organic acid and amino acid accumulation seen during the early stages of development shifted into sugar synthesis during the later stage of citrus fruit development. The expression of invertases remained unchanged, while an invertase inhibitor was up-regulated towards maturation. The increased expression of sucrose-phosphate synthase and sucrose-6-phosphate phosphatase and the rapid sugar accumulation suggest that sucrose is also being synthesized in citrus juice sac cells during the later stage of fruit development

Interlinking showy traits: co-engineering of scent and colour biosynthesis in flowers

The phenylpropanoid pathway gives rise to metabolites that determine floral colour and fragrance. These metabolites are one of the main means used by plants to attract pollinators, thereby ensuring plant survival. A lack of knowledge about factors regulating scent production has prevented the successful enhancement of volatile phenylpropanoid production in flowers. In this study, the Production of Anthocyanin Pigment1 ( Pap1 ) Myb transcription factor from Arabidopsis thaliana , known to regulate the production of non-volatile phenylpropanoids, including anthocyanins, was stably introduced into Petunia hybrida . In addition to an increase in pigmentation, Pap1 -transgenic petunia flowers demonstrated an increase of up to tenfold in the production of volatile phenylpropanoid/benzenoid compounds. The dramatic increase in volatile production corresponded to the native nocturnal rhythms of volatile production in petunia. The application of phenylalanine to Pap1 -transgenic flowers led to an increase in the otherwise negligible levels of volatiles emitted during the day to nocturnal levels. On the basis of gene expression profiling and the levels of pathway intermediates, it is proposed that both increased metabolic flux and transcriptional activation of scent and colour genes underlie the enhancement of petunia flower colour and scent production by Pap1 . The co-ordinated regulation of metabolic steps within or between pathways involved in vital plant functions, as shown here for two showy traits determining plant–pollinator interactions, provides a clear advantage for plant survival. The use of a regulatory factor that activates scent production creates a new biotechnological strategy for the metabolic architecture of fragrance, leading to the creation of novel genetic variability for breeding purposes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75040/1/j.1467-7652.2008.00329.x.pd

Distinct Roles of Jasmonates and Aldehydes in Plant-Defense Responses

BACKGROUND: Many inducible plant-defense responses are activated by jasmonates (JAs), C(6)-aldehydes, and their corresponding derivatives, produced by the two main competing branches of the oxylipin pathway, the allene oxide synthase (AOS) and hydroperoxide lyase (HPL) branches, respectively. In addition to competition for substrates, these branch-pathway-derived metabolites have substantial overlap in regulation of gene expression. Past experiments to define the role of C(6)-aldehydes in plant defense responses were biased towards the exogenous application of the synthetic metabolites or the use of genetic manipulation of HPL expression levels in plant genotypes with intact ability to produce the competing AOS-derived metabolites. To uncouple the roles of the C(6)-aldehydes and jasmonates in mediating direct and indirect plant-defense responses, we generated Arabidopsis genotypes lacking either one or both of these metabolites. These genotypes were subsequently challenged with a phloem-feeding insect (aphids: Myzus persicae), an insect herbivore (leafminers: Liriomyza trifolii), and two different necrotrophic fungal pathogens (Botrytis cinerea and Alternaria brassicicola). We also characterized the volatiles emitted by these plants upon aphid infestation or mechanical wounding and identified hexenyl acetate as the predominant compound in these volatile blends. Subsequently, we examined the signaling role of this compound in attracting the parasitoid wasp (Aphidius colemani), a natural enemy of aphids. PRINCIPAL FINDINGS: This study conclusively establishes that jasmonates and C(6)-aldehydes play distinct roles in plant defense responses. The jasmonates are indispensable metabolites in mediating the activation of direct plant-defense responses, whereas the C(6)-aldehyes are not. On the other hand, hexenyl acetate, an acetylated C(6)-aldehyde, is the predominant wound-inducible volatile signal that mediates indirect defense responses by directing tritrophic (plant-herbivore-natural enemy) interactions. SIGNIFICANCE: The data suggest that jasmonates and hexenyl acetate play distinct roles in mediating direct and indirect plant-defense responses. The potential advantage of this "division of labor" is to ensure the most effective defense strategy that minimizes incurred damages at a reduced metabolic cost

Generation of Phenylpropanoid Pathway-Derived Volatiles in Transgenic Plants: Rose Alcohol Acetyltransferase Produces Phenylethyl Acetate and Benzyl Acetate in Petunia Flowers

Esters are important contributors to the aroma of numerous flowers and fruits. Acetate esters such as geranyl acetate, phenylethyl acetate and benzyl acetate are generated as a result of the action of alcohol acetyltransferases (AATs). Numerous homologous AATs from various plants have been characterized using in-vitro assays. To study the function of rose alcohol acetyltransferase (RhAAT) in planta , we generated transgenic petunia plants expressing the rose gene under the control of a CaMV-35S promoter. Although the preferred substrate of RhAAT in vitro is geraniol, in transgenic petunia flowers, it used phenylethyl alcohol and benzyl alcohol to produce the corresponding acetate esters, not generated by control flowers. The level of benzyl alcohol emitted by the flowers of different transgenic lines was ca. three times higher than that of phenylethyl alcohol, which corresponded to the ratio between the respective products, i.e. ca. three times more benzyl acetate than phenylethyl acetate. Feeding of transgenic petunia tissues with geraniol or octanol led to the production of their respective acetates, suggesting the dependence of volatile production on substrate availability.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43457/1/11103_2005_Article_4924.pd

Biosynthesis and regulation of floral scent in snapdragon and petunia flowers

Floral scent is typically a complex mixture of low molecular weight volatile compounds (100-200 Da) which gives the flower its unique, characteristic fragrance. The major components in the fragrance of snapdragon flowers are the aromatic ester methylbenzoate and two monoterpene olefins, (E)-β-ocimene and myrcene. Petunia floral scent consists almost exclusively of benzenoid/phenylpropanoid-related compounds, and is dominated by methylbenzoate, benzaldehyde, phenylacetaldehyde and benzyl benzoate. Using a functional genomic approach, a cDNA encoding a putative salicylic acid carboxyl methyltransferase (SAMT) was isolated in snapdragon and its potential involvement in the production and emission of methylbenzoate was analyzed. Using a similar approach, genes encoding enzymes potentially responsible for the formation of methylbenzoate and benzylbenzoate and phenyl ethyl benzoate in petunia were isolated and characterized. The molecular mechanisms responsible for postpollination changes in floral scent emission were investigated in snapdragon and petunia flowers using methylbenzoate, one of the major scent compounds emitted by these flowers, as an example. In both species, a pollination-induced decrease in methylbenzoate emission begins only after pollen tubes reach the ovary. Petunia and snapdragon both synthesize methylbenzoate from benzoic acid and S-adenosyl- L-methionine (SAM); however, they use different mechanisms to down-regulate its production after pollination. In petunia, expression of the gene responsible for methylbenzoate synthesis is suppressed by ethylene. In snapdragon, a decrease in S-adenosyl-L-methionine:benzoic acid carboxyl methyltransferase (BAMT) activity and a decrease in the ratio of SAM to S-adenosyl-L-homocysteine ( methylation index ) after pollination are concomitant with the decrease in methylbenzoate emission, and are therefore likely involved in this post-pollination change in emission

Suivi d'une cohorte d'enfants entre 3-4 ans et 7-8 ans (évolution des facteurs de risque de surpoids)

BESANCON-BU Médecine pharmacie (250562102) / SudocSudocFranceF

Novel S-adenosyl-L-methionine:salicylic acid carboxyl methyltransferase, an enzyme responsible for biosynthesis of methyl salicylate and methyl benzoate, is not involved in floral scent production in snapdragon flowers.

Using a functional genomic approach we have isolated and characterized a cDNA that encodes a salicylic acid carboxyl methyltransferase (SAMT) from Antirrhinum majus. The sequence of the protein encoded by SAMT has higher amino acid identity to Clarkia breweri SAMT than to snapdragon benzoic acid carboxyl methyltransferase (BAMT) (55 and 40% amino acid identity, respectively). Escherichia coli-expressed SAMT protein catalyzes the formation of the volatile ester methyl salicylate from salicylic acid with a K(m) value of 83 microM. It can also methylate benzoic acid to form methyl benzoate, but its K(m) value for benzoic acid is 1.72 mM. Snapdragon flowers do not emit methyl salicylate. The potential involvement of SAMT in production and emission of methyl benzoate in snapdragon flowers was analyzed by RNA gel blot analysis. SAMT mRNA was not detected in floral tissues by RNA blot hybridization, but low levels of SAMT gene expression were detected after real-time RT-PCR in the presence of SAMT-specific primers, indicating that this gene does not contribute significantly, if at all, in methyl benzoate production and emission in snapdragon flowers. Expression of SAMT in petal tissue was found to be induced by salicylic and jasmonic acid treatments

Molecular cloning, characterization, and expression analysis of a gene encoding a Ran binding protein (RanBP) in Cucumis melo L.

Ran binding proteins (RanBPs) are highly conserved members of the GTP-binding protein family that are involved in nuclear protein export between the nucleus and the cytoplasm. In this study, a CmRanBP gene from a melon was isolated (Cucumis melo L.) using the RACE (rapid amplification of cDNA ends) method. The 778 basepair long melon, with a RanBP cDNA encoding consisting of 197 amino acids (22.2 kDa protein), was characterized (GenBank accession no: EU853459). The predicted amino acid sequence of CmRanBP was found to be 70% identical to VvRanBP, PtRanBP, and RcRanBP from Vitis vinifera, Populus trichocarpa, and Ricinus communis, respectively. Within the RanBD (Ran binding domain), 5 highly conserved motifs and 1 Ran binding motif were found in all members of the RanBP gene family from various plant species. Expression profiles of the CmRanBP gene in different tissues under high temperature stress were also investigated by semiquantitative RT-PCR. The CmRanBP gene was expressed in a similar manner in the roots, leaves, and stems at 25 degrees C as a control environment. However, when the temperature was raised to 38 degrees C and 40 degrees C, expression levels of the CmRanBP gene were significantly (P < 0.05) increased in the root, leaf, and stem tissues. We show here for the first time that the CmRanBP gene expression was correlated with heat stress responses

Distinct roles of jasmonates and aldehydes in plant-defense responses.

BackgroundMany inducible plant-defense responses are activated by jasmonates (JAs), C(6)-aldehydes, and their corresponding derivatives, produced by the two main competing branches of the oxylipin pathway, the allene oxide synthase (AOS) and hydroperoxide lyase (HPL) branches, respectively. In addition to competition for substrates, these branch-pathway-derived metabolites have substantial overlap in regulation of gene expression. Past experiments to define the role of C(6)-aldehydes in plant defense responses were biased towards the exogenous application of the synthetic metabolites or the use of genetic manipulation of HPL expression levels in plant genotypes with intact ability to produce the competing AOS-derived metabolites. To uncouple the roles of the C(6)-aldehydes and jasmonates in mediating direct and indirect plant-defense responses, we generated Arabidopsis genotypes lacking either one or both of these metabolites. These genotypes were subsequently challenged with a phloem-feeding insect (aphids: Myzus persicae), an insect herbivore (leafminers: Liriomyza trifolii), and two different necrotrophic fungal pathogens (Botrytis cinerea and Alternaria brassicicola). We also characterized the volatiles emitted by these plants upon aphid infestation or mechanical wounding and identified hexenyl acetate as the predominant compound in these volatile blends. Subsequently, we examined the signaling role of this compound in attracting the parasitoid wasp (Aphidius colemani), a natural enemy of aphids.Principal findingsThis study conclusively establishes that jasmonates and C(6)-aldehydes play distinct roles in plant defense responses. The jasmonates are indispensable metabolites in mediating the activation of direct plant-defense responses, whereas the C(6)-aldehyes are not. On the other hand, hexenyl acetate, an acetylated C(6)-aldehyde, is the predominant wound-inducible volatile signal that mediates indirect defense responses by directing tritrophic (plant-herbivore-natural enemy) interactions.SignificanceThe data suggest that jasmonates and hexenyl acetate play distinct roles in mediating direct and indirect plant-defense responses. The potential advantage of this "division of labor" is to ensure the most effective defense strategy that minimizes incurred damages at a reduced metabolic cost