1,720,958 research outputs found
RNA extraction from plant tissue - The use of calcium to precipitate contaminating pectic sugars
No full textSeveral protocols and commercial kits are used for the extraction of nucleic acids from different plant tissues. Although there are several procedures available to remove sugars, which hinder the extraction of clean genomic DNA, there are few to assist with extraction of RNA. Those presently used include precipitations with ethylene glycol monobutyl ether or lithium chloride (LiCl), or centrifugation in cesium chloride (CsCl) gradients, but these generally either do not allow high recovery of RNA, are time consuming, rely on hazardous chemicals or need special equipment. Here we present the use of the simple cation, Ca2+, which has been tested and shown to be very efficient for the precipitation of high molecular weight pectic sugars during RNA extraction. Results are presented for different plant tissues, especially tissues of peach and apple fruits at varying ripening stages
The ethylene biosynthetic and signal transduction pathways are differently affected by 1-MCP in apple and peach fruit
No full text1-Methylcyclopropene (1-MCP) is an antagonist of ethylene for receptor binding sites and the effects of its application differ in relation to a number of factors including genotype and ripening physiology. Peach (Prunus persica L. Batsch cv. 'Summer Rich') and apple (Malus x domestica L. Borkh cv. 'Golden Delicious') fruits were incubated with 1-MCP (1 mu L l(-1)) for 24 h at 20 degrees C and respiration rate, ethylene production and fruit firmness, together with ACC synthase, ACC oxidase, ETR1, ERS1, and CTR1 gene expression patterns were assessed throughout the post-treatment phase. 1-MCP was confirmed to be effective in delaying ripening in apples while in peaches only a limited effect of the chemical was observed. A dramatic inhibition of ethylene biosynthesis and ACS gene expression was induced by 1-MCP in apples whereas no marked difference was observed in peaches between the two controls (in air and in sealed jars without 1-MCP) and the treated fruit. In apples, Md-ETR1 and Md-ERS1 gene expression was down-regulated by 1-MCP starting from the end of the treatment, while Md-CTR1 appeared negatively affected by the chemical at a later stage. Transcription of Pp-ETR1, Pp-ERS1 and Pp-CTR1 genes appeared unaffected in 1-MCP treated peaches. Differences in receptor transcript levels between control fruit maintained in air and those enclosed in sealed jars without 1-MCP may be due to an effect of CO2 that rapidly accumulates following incubation of ripening peaches. Results support the hypothesis that the different behaviour of peaches and apples in response to 1-MCP application might be related to differences in terms of ratio, expression patterns and/or turn-over of the ethylene receptors
Different response of apple and peach fruits to 1-MCP: a case of different sensitivity to ethylene?
No full text1-methylcyclopropene (1-MCP) is known as an antagonist of ethylene action. A number of different trials demonstrated that not all climacteric fruits respond in a similar way to 1-MCP treatment: two examples are represented by apple and peach fruits. When applied on apples, 1-MCP is particularly effective in delaying ripening, while in peaches the rate of softening is slowed down only during the incubation period and a quick recovery of ripening parameters occurs in the post-treatment phase. In order to elucidate this different behavior, specific trials on peaches and apples have been performed. As expected, apple (cv. ‘Golden Delicious’ and ‘Royal Gala’) fruits responded to 1-MCP (0.625 ppm for 24h) maintaining firmness and producing little ethylene for the considered period (24 days) at 20°C, whereas in peaches (cv. ‘Summer Rich’), 1-MCP (1ppm for 24 or 72h) was effective in reducing ethylene evolution and slowing down the softening process only during the incubation time and a short period thereafter. The quick recoveries of ethylene biosynthesis and the softening process observed in peaches during the post-treatment phase are associated with increases of PpACO1 and polygalacturonase (PG) gene expression. A molecular approach was used to investigate the sensitivity of both apples and peaches to ethylene. ETR1 (a member of the ethylene receptor family) gene expression was monitored via RT-PCR and a different behavior between apples and peaches has been observed: in fact, following 1-MCP treatment, MdETR1 transcript accumulation showed a decreasing trend, whereas the amount of PpETR1 mRNA did not significantly change throughout the considered periods
La regolazione ormonale dell’invaiatura della bacca di vite: un possibile modello basato sull’analisi dei profili trascrizionali di bacche trattate con acido naftalenacetico
No full textI meccanismi regolativi attivi durante la maturazione della bacca d’uva sono prevalentemente basati sulle interazioni tra auxina, etilene, acido abscissico (ABA) e brassinosterodi (BR). In particolare, le auxine agiscono come repressori della maturazione, mentre etilene, ABA e BR operano come induttori. Per apportare nuove informazioni sulle interazioni ormonali presenti all’avvio della maturazione (invaiatura) è stato effettuato un trattamento con auxina sintetica (acido naftalacetico, NAA), una settimana prima dell’invaiatura. Il trattamento causa un forte ritardo della progressione degli eventi associati alla maturazione: aumento di dimensione della bacca, accumulo di antociani e zuccheri e riduzione degli acidi organici. Questi eventi sono accompagnati da significative variazioni della trascrizione di geni associati ai metabolismi primario, secondario e ormonale. I dati relativi a questi ultimi sono stati analizzati mediante HORMONOMETER, uno strumento bioinformatico che consente di valutare gli effetti dell’applicazione di ormoni e le loro interazioni sulla base di dati trascrittomici. I risultati ottenuti evidenziano che, a sette giorni dal trattamento, le concentrazioni di auxina tornano a livelli biologicamente compatibili grazie all’attivazione di un processo di omeostasi. Questa ipotesi è suffragata da analisi di trascritti (via qPCR) che mostrano un’induzione di geni coinvolti nella coniugazione (GH3-like) della auxine e di quelli che ne regolano l’azione (IAA4- e IAA31-like). Per quanto attiene alle interazioni è stato osservato che l’NAA induce i geni della biosintesi dell’etilene (ACS e ACO) ma esercita un forte effetto negativo su quelli associati alla sua percezione (EIN4) ed azione (ERFs). A questo si contrappone un inaspettato effetto sinergico, seppur limitato, delle auxine sulla catena trasduttiva dell’ABA. L’insieme dei dati ottenuti è stato organizzato in un modello della regolazione ormonale dell’invaiatura che sarà presentato e discusso
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
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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