1,721,025 research outputs found
Flavonoid metabolomics in Gerbera hybrida cultivars
No full textFlavonoids, common to all land plants, are synthesized via the phenylpropanoid pathway. Phenylalanine ammonia lyase catalyzes the first reaction of this pathway (conversion of phenylalanine to cinnamate), which is followed by a set of about ten enzymes catalyzing reactions to flavones, flavonols and anthocyanins (Fig.1). Anthocyanin pigments are responsible for pink, orange and purple to blue colors in petals.
Flavonoids in our model ornamental plant Gerbera hybrida consist of three subgroups, flavones, flavonols and anthocyanins. Most of the anthocyanins accumulate in the adaxial epidermi of petals and give the different cultivars their different color. Both pelargonidin and cyanidin derivatives are found in gerbera, but none of the cultivars contain delphinidin.
According to chromatographic and MS analysis for ray flowers of more than 22 cultivars in different developmental stages, we observed that pelargonidin-type Gerbera cultivars accumulated only the favone apigenin, while cyanidin-type cultivars accumulated luteolin. However, the biosynthesis of flavonols was different, quercetin was observed in both pelargonidin and cyanidin-type cultivars.
Based on chemical analysis, RNA sequencing and enzyme assays, we are trying to understand the biosynthetic pathway of flavonoids in differentGerbera cultivars. Different aspects in the timing of gene expression encoding isoenzymes e.g. F3’H and DFR across developmental stages seems important for determination of the flavonoid pattern in the inflorescence
Metabolons and the biosynthesis of Gerbera hybrida flavonoids
Full text linkThe formation of protein complexes, metabolons, and the channeling of intermediates of secondary metabolism has
been discussed for at least 30 years. Metabolons and channeling enable plants to perform a highly effective synthesis of specific natural products without or with
reduced metabolic interference and avoiding accumulation of toxic intermediates. In spite of a long tradition of the concept, precise examples of complete metabolons are very scarce.
Our aim is to define flavone and anthocyanidin specific metabolons in the ornamental plant Gerbera hybrida. Our earlier data shows that specific genes are expressed early in development PAL and CHS3 and others late PAL, CHS1 and DFR, possibly correlating with flavone and anthocyanin
biosynthesis. Furthermore, transformation of the pelargonidin type Gerbera cultivar Terra Regina with a MYB-type regulatory gene induces cyanidin biosynthesis without interfering with the background pelargonidin biosynthesis. Using our large set of EST, the expanding genomic sequence resource of Gerbera and new data from Illumina sequences for wild type of Regina and MYB transgenic lines, we are establishing correlations in expression and patterns of protein-protein
interactions for the whole flavonoid metabolism isoenzyme complex in our model plant
Anthocyanin biosynthesis mystery in gerbera cultivars Estelle and Ivory
Full text linkFlavonoids in our model ornamental plant Gerbera hybrida, consist of three subgroups, flavones, flavonols and anthocyanins. Anthocyanins accumulate in the adaxial surface of petals and give the different cultivars their different color. Both pelargonidin and cyanidin derivatives are found in gerbera, but none of the cultivars contain delphinidin.
The acyanic cultivar Ivory is a sport of the pelargonidin containing pink cultivar Estelle, i.e., it originates from an acyanic branch of Estelle. Ivory is apparently a transposon mutant of Estelle, since revertant sectors are regularly observed (Figure 1). In spite of complete loss of anthocyanin pigmentation, all genes encoding enzymes necessary for pelargonidin biosynthesis (PAL, C4H, 4CL, CHS, CHI, F3H, F3’H, DFR, and ANS) are expressed in Ivory at similar levels as in Estelle.
We performed a comprehensive flavonoid analysis using UHPLC MS/MS for Estelle and Ivory, collecting samples from whole ray flower petals and from their isolated adaxial epidermi. Except for pelargonidin derivatives, which are present in Estelle but lack nearly completely from Ivory, we found that both cultivars have similar amounts of flavones and flavonoids (mainly apigenin and kaempherol glycosides).
We further analyzed the cultivars using RNA sequencing and produced on average 10 million Illumina reads from two developmental stages of Estelle and Ivory petals. Mapping of the reads to an assembly of gerbera Sanger (1), 454 and Illumina reads confirms that all anthocyanidin biosynthesis genes are expressed similarly in the two samples. Surprisingly, none of the assembled contigs show differential expression between these two cultivars.
Although dramatically different to the eye, the difference in Estelle and Ivory at transcript level eludes our attempts of analysis. Pelargonidin biosynthesis is intact at least up to the point of dihydrokaempherol synthesis. In reads mapping to transcripts for DFR and ANS we have not observed anomalies that would be indicative of a transposon insertion. None of the glucosyl transferase encoding transcripts are down regulated or anomalous either. However, we do not have biochemical evidence which one of the contigs would encode the gerbera anthocyanidin 3-O-glucosyltransferas
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
A vacuolar sorting domain may also influence the way in which proteins leave the endoplasmic reticulum
No full textProtein sorting to plant vacuoles is known to be dependent on a considerable variety of protein motifs recognized by a family of sorting receptors. This can involve either traffic from the endoplasmic reticulum (ER) through the Golgi apparatus or direct ER-to-vacuole transport. Barley aspartic protease (Phytepsin) was shown previously to reach the vacuole via trafficking through the Golgi apparatus. Here we show that Phytepsin normally exits the ER in a COPII-mediated manner, because the Phytepsin precursor accumulates in the ER upon specific inhibition of the formation of COPII vesicles in vivo. Phytepsin differs from its yeast and mammalian counterparts by the presence of a saposin-like plant-specific insert (PSI). Deletion of this domain comprising 104 amino acids causes efficient secretion of the truncated molecule (Phytepsin Delta PSI) without affecting the enzymatic activity of the enzyme. Interestingly, deletion of the PSI also changes the way in which Phytepsin exits the ER. Inhibition of COPII vesicle formation causes accumulation of the Phytepsin precursor in the ER but has no effect on the secretion of Phytepsin Delta PSI. This suggests either that vacuolar sorting commences at the ER export step and involves recruitment into COPII vesicles or that the PSI domain carries two signals, one for COPII-dependent export from the ER and one for vacuolar delivery from the Golgi. The relevance of these observations with respect to the bulk flow model of secretory protein synthesis is discussed
Variations on the Author
Full text link“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
Full text linkWe 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
Full text linkWe 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
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