1,721,025 research outputs found
Regulation of nitrate and sulfate uptake in maize genotypes in response to the availability of nitrate
No full textExpression of a putative high-affinity NO3- transporter and of a H+-ATPase in relation to whole plant nitrate transport physiology in two maize genotypes differently responsive to low nitrogen availability
No full textTwo maize genotypes differently responsive to nitrogen availability were characterized for their efficiency in nitrate accumulation via both the LATS (Low‐Affinity Transport System) and HATS (High‐Affinity Transport System) nitrate uptake systems. In addition, a full‐length cDNA encoding a putative high‐affinity nitrate transporter (ZmNrt2.1) was isolated and its expression evaluated in both the roots and leaves of the two maize genotypes, together with the expression of a maize H+‐ATPase isoform (Mha1). The data showed the importance of the iHATS (Inducible High‐Affinity System) system efficiency as a physiological marker of adaptation to low input and suggested that the transcript accumulation of ZmNrt2.1 might be a key step for the regulation of iHATS. However, ZmNrt2.1 transcription cannot account for the differences found between the two hybrids in terms of the activity of their respective iHATS and, as a consequence, of their adaptation to low input. Therefore, the involvement of some other transporter(s) or of some post‐transcriptional/post‐translational mechanism of regulation affecting the efficiency of iHATS may be hypothesized. In addition, the data suggest that the transcription of the Mha1 gene may also be involved in the global efficiency of the iHATS system
Foscolo, Manzoni e la cerchia di Byron: la prima ricezione inglese della Ricciarda e del Carmagnola
Full text linkInternational audienceUn certain nombre de témoignages, connus ou inédits, d’Alessandro Manzoni, Goethe, Cousin et Sainte-Beuve indiquent chez Foscolo l’inspirateur, voir l’auteur des critiques sévères à l’encontre du Comte de Carmagnole et, plus en général, de l’œuvre dramatique de Manzoni publiées, en 1820, par la «Quarterly Review» de John Murray. Cette contribution essaye de reconstruire les circonstances qui amenèrent à la publication de l’article Italian Tragedy, paru anonyme dans le numéro du mois d’octobre 1820 de la prestigieuse revue anglaise sous la forme d’un compte rendu de trois tragédies contemporaines : d’une part Le Comte de Carmagnole, accusé d’être une « feeble tragedy », de l’autre Ricciarda de Foscolo et Francesca da Rimini de Silvio Pellico, célébrées comme étant deux des exemples les plus réussis du nouveau théâtre tragique italien. Attribué généralement à Henry Hart Milman, auteur dramatique et professeur de poésie à Oxford à partir de 1821, l’article s’avère le fruit d’une large collaboration qui impliqua Foscolo et John Cam Hobhouse (co-auteurs, deux ans auparavant, de l’Essay on the Present Literature of Italy), John Murray et, tangentiellement, Lord Byron qui, à Milan en 1816, avait commencé à traduire la tragédie de Pellico avec son ami Hobhouse. La reconstruction de cet épisode complexe permet d’une part de retracer les raison qui, en 1820, suggérèrent à Foscolo la publication en Angleterre de Ricciarda, restée inédite après sa création en Italie, en 1813 ; d’autre part, de s’interroger sur les raisons qui poussèrent Foscolo, en 1826-27, à reprendre sa réflexion autour du genre dramatique. En outre, elle offre l’occasion pour dresser un bilan d’un débat européen, vaste mais peu étudié, autour du théâtre tragique, des unités aristotéliciennes et du rapport entre poésie et histoire qui, à la suite de la publication du Comte de Carmagnole et d’Adelchi mais aussi des interventions de Goethe, Fauriel, Visconti et Manzoni, trouva pendant plusieurs mois un large écho dans les périodiques allemands, anglais, italiens et français.A partire da alcune affermazioni, edite e inedite, di Manzoni e Goethe, Cousin e Sainte-Beuve secondo cui Foscolo, durante l’esilio londinese, avrebbe criticato dalle pagine della «Quarterly Review» il Conte di Carmagnola e, più in generale, l’opera drammatica manzoniana, questo contributo prova a ricostruire le vicende che ispirarono e accompagnarono la pubblicazione dell’articolo Italian Tragedy, apparso adespoto nel 1820 sulla prestigiosa rivista inglese come recensione da un lato al Carmagnola, stroncato come «feeble tragedy», e dall’altro alla Ricciarda di Foscolo e alla Francesca da Rimini di Pellico, lodate invece come massimi esempi tragici della nuova generazione di autori drammatici italiani. Tradizionalmente attribuito a Henry Hart Milman, dal 1821 professore di poesia a Oxford e anch’egli tragediografo, l’articolo si rivela invece come l’esito di un’ampia collaborazione che sembra aver coinvolto Foscolo, l’editore John Murray, John Cam Hobhouse (co-autore con Foscolo dell’Essay on the Present Literature of Italy) e, tangenzialmente, anche Lord Byron (che, a Milano nel 1816, proprio con l’amico Hobhouse aveva iniziato a tradurre la tragedia di Pellico). L’intricata vicenda porta a ricostruire le motivazioni della pubblicazione in Inghilterra, nel 1820, della Ricciarda, terminata in Italia nel 1813 ma rimasta inedita fino ad allora, e a interrogarsi sulle ragioni del ritorno di Foscolo, nel suo ultimo anno di vita, alla riflessione critica sul genere drammatico. Inoltre, essa fornisce l’occasione per fare il punto su un ampio dibattito europeo, poco studiato, che, sulla spinta della pubblicazione del Carmagnola e dell’Adelchi, così come degli scritti critici di Goethe, Fauriel, Visconti e Manzoni stesso, si sviluppò in quei mesi sulle riviste tedesche, inglesi, italiane e francesi in merito al teatro tragico, alle unità aristoteliche e al rapporto tra poesia e storia
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
Chromate differentially affects the expression of a high-affinity sulfate transporter and isoforms of components of the sulfate assimilatory pathway in Zea mays (L.)
No full textn this study the chromate accumulation and tolerance were investigated in Zea mays L. in relation to sulfur availability since sulfate may interact with chromate for transport into the cells. Chromate inhibited sulfate uptake when supplied to plants for a short-term period, whereas phosphate uptake remained unchanged. Sulfate absorption was also reduced in S-starved (-S) and S-supplied (+S) plants treated for 2 d with 0.2 mM chromate and the concomitant repression of the root high-affinity sulfate root transporter ZmST1;1 transcript accumulation was observed. Conversely, the plasma membrane H+-ATPase Mha2 was unaffected by chromate in +S plants, allowing to exclude a general effect of chromate on the active membrane transport. As observed for sulfate uptake, chromate uptake was enhanced in -S condition and decreased in both +S and -S plants after 2 d of Cr treatment. Chromate reduced the concentration of sulfur and sulfate in +S plants to the basal level of -S plants, and maximum chromium accumulation was recorded in S-deprived plants. Analysis of transcript abundance of genes involved in sulfate assimilation revealed differential regulation by chromate, which was only partly related to sulfur availability and to the levels of thiols. This work shows for the first time that chromate specifically represses sulfate uptake, and such repression occurs without the implication of the candidate regulatory metabolites of the sulfate transport system in plants
Expression of two maize putative nitrate transporters in response to nitrate and sugars availability
No full textA full-length cDNA encoding a putative high-affinity nitrate transporter (ZmNrt2.2) from maize was isolated and characterised, together with another previously identified transporter (ZmNrt2.1), in terms of phylogenesis, protein structure prediction and regulation of transcript accumulation in response to nitrate and sugar availability. The expression of both genes was evaluated by quantitative and semi-quantitative RT-PCR in response to nitrate and sugar supply and the in planta localisation of mRNA was studied by in situ hybridisation. Data obtained suggested similar genetic evolution and identical transmembrane structure prediction between the two deduced proteins, and differences in both regulation of their expression and mRNA localisation in response to nitrate, leading us to hypothesise a principal role for ZmNRT2.1 in the influx activity and the major involvement of ZmNRT2.2 in the xylem loading process. Our data suggest opposing sugar regulation by ZmNrt2.1 and ZmNrt2.2 transcription in the presence or absence of nitrate and the existence of both hexokinase-dependent and hexokinase-independent transduction mechanisms for the regulation of ZmNrt2.1 and ZmNrt2.2 expression by sugars
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