1,721,009 research outputs found
Indagini sul ruolo della poligalatturonasi nella rizottoniosi del cavolfiore.
No full textNel corso di un censimento delle malattie del cavolfiore in Campania, la Rhizoctonia solani Kuhn è stata isolata con frequenza piuttosto elevata da piante presentanti gravi alterazioni dei tessuti corticali a livello del colletto. La gravità della malattia, riscontrata fra l'altro in tutte le principali pIaghe orticole della regione, ci ha indotti da una parte a studiare la resistenza varietale del cavolfiore alla R. solani e dall'altra a intraprendere una ricerca sull'attività enzimatica del fungo. Già alcuni Autori hanno dedicato la loro attenzione a questo ultimo argomento. Bateman, studiando l'attività cellulosolitica (7) e pectolitica (4) della R. Solani, ha evidenziato sia in vitro che in vivo una poligalatturonasi che ritiene responsabile dell'azione macerante (5). Altri Autori hanno mostrato che la R. solani produce anche poligalatturonico e pectina transcliminasi (3, 22). La capacità della R. solani di sintetizzare poligalatturonasi e cellulasi in coltura è stata messa in relazione con la grandezza dei propaguli del fungo (15); la produzione di questi enzimi inoltre è stata studiata in rapporto allo sviluppo delle lesioni su ipocotili di fagiolo durante i primi stadi della malattia (24). Tuttora però non è stato considerato il ruolo degli enzimi pectolitici e cellulosolitici nella patogenesi della rizottoniosi del cavolfiore, né è stato approfondito lo studio delle proprietà chimico-fisiche di questi enzimi
Endopoligacturonase from Rhizoctonia fragariae: Purification and characterization of two isoenzymes.
No full textAn electrophoretically homogeneous preparation of endo-polygalacturonase (poly(1,4-α-d-galacturonide)glycanohydrolase, EC 3.2.1.15) from culture filtrates of Rhizoctonia fragariae, a pathogenic agent in strawberry plants, was resolved into two isoenzymes when subjected to isoelectrofocusing in a narrow pH range. The isoelectric points of the two isoenzymes were 6.76 ± 0.03 and 7.08 ± 0.05. The two polygalacturonases exhibited similar substrate specificity, pH optimum and pattern of degradation of sodium polypectate. The two enzymes consisted of a sigle polypeptide chain which had an apparent molecular weight of 36 000 as determined by gel filtration on Sephadex G-100
CONSTITUTIVE EXPRESSION OF PECTIN METHYLESTERASE INHIBITORS LIMITS TOBAMOVIRUS SPREADING IN TOBACCO AND ARABIDOPSIS
No full textPlant viral infection is a complex process influenced by the interaction of virus-encoded proteins and host factors which support virus replication and movement. Successful infection requires viral movement proteins (MPs) that modify the plasmodesmata (PD) size exclusion limit during the cell-to-cell movement. Pectin methylesterase (PME) was shown to interact in vitro with the MP of different viruses and the MP-PME interaction was proposed to be necessary for Tobacco mosaic virus (TMV) cell-to-cell spreading. PME is also required for the systemic movement of TMV through the host vasculature. Pectin demethylation directed by PME is likely to be a source of methanol that has been recently found to facilitate TMV spreading by triggering PD dilation. We here report that the ectopic expression of a PME inhibitor from Actinidia chinensis (AcPMEI) in Nicotiana tabacum significantly delays the TMV cell-to-cell and systemic spreading. A reduced susceptibility against Turnip vein clearing virus (TVCV) was also observed in Arabidopsis plants overexpressing a PME inhibitor from Arabidopsis (AtPMEI-2). Overall, our results indicate PMEIs as efficient tools to limit Tobamovirus infection
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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