1,720,966 research outputs found
Characterization of a bZIP transcription factor that regulates the phenylpropanoid pathway in grapevine
Get PDFIn grapevine (Vitis vinifera L.) flavonoids accumulate preferentially in the skin and seeds of grapes (Downey et al. 2004) determining the colour but also the final flavour and astringency of red and white wines. Furthermore, flavonoids extracted from grape berries and seeds exhibit strong nutraceutical potential with a broad spectrum of pharmacological and therapeutic effects (Nassiri-Asl and Hosseinzadeh 2009). Although the general flavonoid pathway has been genetically and biochemically elucidated in many plant species and most recently also in grapevine (Hichri et al. 2011), its regulation still remains not completely characterized.
In this study we report the characterization of a grapevine bZIP transcription factor involved in flavonoid biosynthesis regulation. According to the ten-classes classification proposed in Arabidopsis, this VvbZIP belongs to the S-group of bZIP. Its expression along fruit development is higher at the flowering stage and is induced by UV-B treatment. The overexpression of VvbZIP in tobacco transgenic lines positively correlates with the flower content of quercetin and cyanidin in the glycosilated form. Furthermore, transient expression assays by bombardment of grapevine suspension cultures, have revealed that VvbZIP activates the flavonoid pathway at different sites and through the interaction with other co-factors
Characterization of a bZIP factor that regulates the flavonoid pathway in grapevine
No full textFlavonoids compose one of the most abundant and important subgroups of secondary metabolites detected so far in higher plants. They are involved in several aspects of plant development and defence. Besides the attraction of pollinators and dispersers to fruits and flowers, flavonoids also protect against a plethora of stresses including pathogen attack, wounding and UV irradiation. Flavonoid content and composition of fruits and plant products have been associated with fruit quality including taste, colour and health-promoting effects (Czemmel et al., 2012).
In grapevine (Vitis vinifera L.) flavonoids accumulate preferentially in the skin and seeds of grapes (Downey et al., 2004) determining the colour but also the final flavour and astringency of red and white wines. Furthermore, flavonoids extracted from grape berries and seeds exhibit strong nutraceutical potential with a broad spectrum of pharmacological and therapeutic effects (Nassiri-Asl and Hosseinzadeh, 2009).
The synthesis of these compounds is mainly regulated at transcriptional level. Flavonoids accumulate at specific stages and in specific tissues during flower and berry development, as a consequence of the timely expression of the genes necessary for their synthesis. Although the general flavonoid pathway has been genetically and biochemically elucidated also in grapevine, its regulation still remains not completely characterized (Hichri et al., 2011). Similarly knowledge is still lacking about the molecular basis of the varietal variability in terms of quality and quantity of flavonoids.
To shed light on this issue a mapping population derived from the cross Syrah x Pinot Noir segregating for flavonoid content was characterized at the metabolic and transcriptional level. The transcriptome analysis of the extreme genotypes of the population has allowed the identification of a set of differentially expressed genes. Among them, a basic leucin zipper transcription factor (VvbZIP) has been selected and further characterized to elucidate its role in regulating flavonoid biosynthesis.
A phylogenetic analysis of all the 55 predicted grapevine bZIP factors was performed. According to the ten-classes classification proposed in Arabidopsis, VvbZIP belongs to the S-group of the family.
The analysis of the different classes of flavonoids and of VvbZIP expression in Pinot Noir samples collected from flowering to technological maturity (18°Brix), showed a peak of VvbZIP expression as well as of the flavonols quercetin and kaemperol at flowering time.
A further evidence of the role of this gene in flavonols regulation came from the analysis of Chardonnay plants exposed to UV-light and monitored over a 3-d time period. The light treatment caused an induction of the VvbZIP, VvFLS1 and VvMYBF1 transcripts within the first 10 h, followed by the accumulation of flavonols at 24 h post treatment.
To test the in-planta function, VvbZIP was stably overexpressed into tobacco plants (Nicotiana tabacum). The overexpression of VvbZIP observed in 7 transgenic lines positively correlated with the flower content of quercetin, kaempferol and cyanidin in the glycosilated form suggesting a broader regulatory role of this factor.Luciferase reporter-assays carried out by bombardment of Chardonnay suspension cultures (Czemmel et al., 2009), revealed that VvbZIP binds to the promoters of VvCHS, VvFLS1, VvANR genes activating their transcription, likely through the interaction with other co-factors such as MYBF1 and MYBPA1
A multidisciplinary approach to understand the control of flavonol synthesis in grape berry
No full textFlavonols are flavonoids found in most higher plants, usually in glycosidic forms. They are products of the flavonoid biosynthetic pathway, which also give rise to anthocyanins and to condensed tannins in grapes. In grapevine, they are predominantly synthesized in inflorescence and berry skin, while no detectable levels are found in pulp or seeds (Downey et al., 2003). They act as UV-protectants and as anthocyanin co-pigments in flowers and fruits. For this reason they play a role in defence and pollinators attraction and in conferring stability to the colour of red wines.
Although the general flavonol pathway has been genetically and biochemically elucidated in many plant species and most recently also in grapevine (Matus et al., 2009), (Czemmel et al., 2009), its regulation still remains not completely characterized.
A population from the cross Syrah x Pinot Noir, segregating for the flavonol content, is being studied to identify the genetic determinants of flavonol accumulation in the berry cells by a biochemical and transcriptional characterization. Individuals of the progeny showing high- and low- flavonol content were selected and characterized at different stages of berry development by a microarray approach. Among the differentially expressed identified genes, we focused our attention on a transcription factor not yet characterized in grapevine. To prove its involvement in the control of flavonoid pathway we identified its targets by a promoter assay approach and we analyzed the phenotype of transgenic tobacco lines overexpressing this gene. Preliminary results will be presented.
References
Downey et al. .2003. Synthesis of flavonols and expression of flavonol synthase genes in the developing grape berries of Shiraz and Chardonnay (Vitis vinifera L.). Aust J Grape and Wine Res, 9: 110-121
Matus et al. (2009). Post-veraison sunlight exposure induces MYB-mediated transcriptional regulation of anthocyanin and flavonol synthesis in berry skins of Vitis vinifera. J Exp Bot;60(3):853-67
Czemmel et al. (2009). The grapevine R2R3-MYB transcription factor VvMYBF1 regulates flavonol synthesis in developing grape berries. Plant Physiol, 151:1513-30
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The Basic Leucin-Zipper factor VvBZIP6 is involved in the regulation of the flavonoid pathway in grapevine
Get PDFIn grapevine (Vitis vinifera L.) flavonoids compose one of the most abundant subgroups of secondary metabolites. They accumulate preferentially in the skin and seeds of grapes and fulfill several important functions: i) they mediate the response to biotic and abiotic stresses(temperature, UV-light, nutrition, water deficit); ii) they provide pigmentation to flowers and fruits, thereby influencing quality and typicity of wines. They have been also associated to the observed health-promoting effects ascribed to grape rich diet including wine.
The biosynthesis of these compounds is mainly regulated at the transcriptional level by controlling the genes of the so called general flavonoid pathway which has been genetically and biochemically elucidated in several species including grapevine. Regulation of the structural genes of the pathway is however still not completely elucidated.
In this study we report the characterization of one of the 55 predicted grapevine bZIP genes, VvbZIP6, to be involved in flavonoid biosynthesis regulation. Analysis of its expression during Pinot Noir development revealed that this transcript is very abundant at flowering time concomitantly with the peak of the flavonols quercetin and kaemperol. Chardonnay leaves exposed to UV-light showed an induction of VvbZIP6 within the first 10 h, followed by the accumulation of flavonols at 24 h post treatment. The overexpression of VvbZIP6 in tobacco transgenic lines positively correlates with the flower content of flavonol compounds such as quercetin and kampferol but also glycosilated cyanidin and proanthocyanidins pointed towards a role as a general regulator of the grapevine flavonoid pathway. This has been confirmed by luciferase reporter-assays in Chardonnay suspension cultures showing that VvbZIP6 induces the promoters of VvCHS, VvFLS1, VvANR genes likely via interaction with other co-factors
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
