1,721,014 research outputs found
ANALYSIS OF PECTINOLYTIC ENZYMES AND RELATED GENES IN PYRENOPHORA SPP.
No full textPyrenophora graminea Ito e Kuribayshi and P.teres (Died.) Drechsl. respectively cause leaf stripe and net blotch on barley leaves. Both pathogens are seed-borne and can systemically colonize their host. In contrast to P.teres, P. graminea cannot successfully cause disease by direct leaf infection. Since in the most part of their life cycle both pathogens show an intercellular mode of growth in host tissue, it was assumed that enzymes degrading pectic components of plant cell walls are involved in colonization.
Previous results showed in Pyrenophora graminea cultured in several media containing pectin high a pectinolytic activity revealed by enzymatic assay while a faint expression of endopolygalacturonase (endo-PG) in Northern blot when RNAs were probed to a heterologous gene (clone pCC2 derived from Fusarium moniliforme). Further by PCR experiments in Pyrenophora graminea (strain I2-88) and Pyrenophora teres (I4-88) a genomic region between specific primers (inferred by the Fusarium moniliforme endo-PG gene sequence) has been amplified in both species: Pg2-PCR and Pt4-PCR respectively. Both PCR product were 1.5Kbp. Pg2-PCR has been used as a homologous probe in Northern blot experiments on P.graminea and P.teres RNAs in vitro induced by pectin or barley cell walls, compared to control RNAs. A strong expression has been detected in both fungi although it was constitutive and the transcript was at a lower mw (about 1Kbp) compared to the previous one recognized by pCC2 in P.graminea and to the one identified in F.moniliforme. Furthermore the probe Pg2-PCR apparently belongs only to Pyrenophora spp. genome since it does not recognize Fusarium moniliforme sequences neither in Northern blot nor in Southern blot experiments.
Further analysis will focus on Pg2-PCR cloning and sequencing to identify both structure and function of the relative gene.
A concomitant study about P.graminea secreted polygalacturonase activity showed a very high endo-PG activity in cultures containing pectin, an about ten-fold lower activity in cultures containing cell walls and only barely detectable activity in control cultures.
Isoelectrofocusing patterns were equivalent in both inductive systems. The two main bands (42 kD and 40 kD, Ip about 8.5 and 7.5 respectively) were recognized in Western blot by a Fusarium moniliforme anti-PG polyclonal antibody.
What is the significance of different results obtained by those two approaches is still an open question: on one side a constitutive gene function identified only by the homologous probe Pg2-PCR, on the other side an inducible activity identified by the heterologous antibody. Multiple forms of PG may exist in Pyrenophora spp. with different expression modes. It is noteworthy that both approaches produce equivalent results with two inductive systems (pectin and cell walls) suggesting a role of the same PGs in host-pathogen interaction.
Pyrenophora graminea Ito e Kuribayshi and P.teres (Died.) Drechsl. respectively cause leaf stripe and net blotch on barley leaves. Since both pathogens show an intercellular mode of growth in part of their life cycle, pectinolitic enzymes could be important for host colonization.
A 1.5 Kbp PCR product (Pg2-PCR), previously obtained from P.graminea with specific primers from Fusarium moniliforme endo-PG gene sequence, has been used as a homologous probe in Northern blot experiments
The expression of a bean PGIP in transgenic wheat confers increased resistance to the fungal pathogen Bipolaris sorokiniana
No full textA possible strategy to control plant pathogens is the improvement of natural plant defense mechanisms against the tools that pathogens commonly use to penetrate and colonize the host tissue. One of these mechanisms is represented by the host plant’s ability to inhibit the pathogen’s capacity to degrade plant cell wall polysaccharides. Polygalacturonase- inhibiting proteins (PGIP) are plant defense cell wall glycoproteins that inhibit the activity of fungal endopolygalacturonases (endo-PGs). To assess the effectiveness of these proteins in protecting wheat from fungal pathogens, we produced a number of transgenic wheat lines expressing a bean PGIP (PvPGIP2) having a wide spectrum of specificities against fungal PGs. Three independent transgenic lines were characterized in detail, including determination of the levels of PvPGIP2 accumulation and its subcellular localization and inhibitory activity. Results show that the transgene-encoded protein is correctly secreted into the apoplast, maintains its characteristic recognition specificities, and endows the transgenic wheat with new PG recognition capabilities. As a consequence, transgenic wheat tissue showed increased resistance to digestion by the PG of Fusarium moniliforme. These new properties also were confirmed at the plant level during interactions with the fungal pathogen Bipolaris sorokiniana. All three lines showed significant reductions in symptom progression (46 to 50%) through the leaves following infection with this pathogen. Our results illustrate the feasibility of improving wheat’s defenses against pathogens by expression of proteins with new capabilities to counteract those produced by the pathogens
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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