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CHARACTERIZATION OF 2 SCLEROTINIA-SCLEROTIORUM POLYGALACTURONASES WITH DIFFERENT ABILITIES TO ELICIT GLYCEOLLIN IN SOYBEAN
No full textTwo endo-polygalacturonase isoenzymes (PG-II and PG-IV), with masses of 34 and 30 kDa respectively, were purified from soybean hypocotyls infected by Sclerotinia sclerotiorum. The pH optimum for both isoenzymes was about 4.6, but PG-IV exhibited a broader range of pH activity. PG-IV showed a much higher affinity for pectin than did PG-II. PG-II hydrolyzed polygalacturonic acid in a more random fashion than PG-IV. Oligouronides produced by PG-II showed a higher phytoalexin elicitor activity. PG-IV produced a large degree of maceration of soybean hypocotyls releasing a significant amount of uronides. The properties of PG-II and PG-IV are discussed in relation to the different ability of the two isoenzymes to elicit glyceollin in soybean
PURIFICATION AND MOLECULAR CHARACTERIZATION OF A SOYBEAN POLYGALACTURONASE-INHIBITING PROTEIN
No full textA polygalacturonase-inhibiting protein (PGIP) was detected in soybean (Glycine max (L.) Merr.) seedlings. The protein was purified from germinating seeds and appeared to consist of at least three components with very close molecular weights (between 37 and 40 kDa) but each showing a unique N-terminal sequence. Primers specific for N-terminal and C-terminal nucleotide sequences of field bean (Phaseolus vulgaris L.) PGIP were used in a polymerase chain reaction (PCR) on soybean DNA, and only one amplification band was obtained. The amplified product was cloned and one of the PCR clones was sequenced. The nucleotide sequence comprises 942 bp with a single open reading frame which encodes a polypeptide of 313 amino-acid residues with a predicted molecular weight of 33984 Daltons and an isoelectric point of 8.21. Analysis of genome organization showed a single gene copy of PGIP with few related sequences, and wounding of soybean hypocotyls showed a strong induction of expression of the PGIP gene. The PGIP showed different activities toward three purified fungal endo-polygalacturonases (endo-PGs) (two endo-PGs from Sclerotinia sclerotiorum and one endo-PG from Aspergillus niger). A possible involvement of soybean PGIP in plant defence against fungal pathogens is discussed
Polygalacturonase inhibiting proteins from Allium porrum L. and their role in plant tissue against fungal endo- polygalacturonases
No full textFive endo-polygalacturonases (PGs), three produced in culture filtrate by Fusarium moniliforme, Sclerotium cepivorum and Botrytis aclada, respectively, and two (one acidic and one basic isoform) obtained from Sclerotinia sclerotiorum soybean infected hypocotyls, were purified in order to characterize the activity of polygalacturonase inhibitor(s) (PGIP(s)) from leek stalk tissue (Allium porrum L.). Three apparently different PGIPs (PGIP-I, PGIP-II and PGIP-III) were purified from the leek tissue. The two more abundant PGIPs (PGIP I and PGIP-III), although possessing similar pIs of about 6.5, differed in chromatographic behaviour, their molecular mass (39 and 42 kDa, respectively), and specific activity when assayed with the fungal endo-PGs. In addition, PGIP-I was solubilized from tissue homogenate with a low-salt buffer whilst PGIP-III needed a high-salt buffer for extraction (behaving as an ionically wall-bound protein). PGIP-II had very similar properties to PGIP-I, but was extracted using the high-salt buffer. The purified PGIPs and the crude leek extract showed similar inhibition activity patterns against the five fungal endo-PGs. The maximum inhibition activity was observed against the basic endo-PG from S. sclerotiorum, followed by the acidic endo-PG of S. sclerotiorum and the endo-PG from B. aclada. In contrast, no inhibition of endo-PGs from S. cepivorum and F. moniliforme was observed. Four different concentrations of the five fungal endo-PGs were incubated separately with slices of leek stalk, and the galacturonides released in the incubation mixture were measured. At every level used the endo-PGs off. moniliforme and S. cepivorum showed the maximum activity in uronide releasing. The endo-PGs of S. sclerotiorum (acidic PG) and B. aclada were active only when high levels were used while the basic endo-PG of S. sclerotiorum was not active in combustion with any level of PGIP. These results indicate that a close relationship exists between PGIP activity in vitro and the ability of PGIP to protect leek tissue from endo-PG degradation
DIFFERENTIAL ABSORPTION AND LOCALIZATION OF 2 SCLEROTINIA- SCLEROTIORUM ENDO-POLYGALACTURONASES IN SOYBEAN HYPOCOTYLS
No full textThe isolate B-24 of the necrotrophic fungus Sclerotinia sclerotiorum produces two major endo-polygalacturonases (PG-II and PG-IV) during infection of soybean seedlings. By a combination of biochemical, immunofluorescence and morphological techniques it was shown that they were differentially absorbed by soybean hypocotyl tissue, becoming located preferentially at different sites. PG-IV was absorbed much more than PG-II and it was able to permeate the unwounded surface of the hypocotyl and accumulate in the cortical cell layer where it produced an increase of autofluorescence and a marked loss of adhesion of cortical cells. When applied to the cut-end surface of the hypocotyl PG-IV remained localized near the site of the treatment. In contrast PG-II was not absorbed through the epidermis but, when applied to the cut surface of hypocotyl it was transported some distance into the tissue possibly via the vascular bundles, The different behaviour of the two PGs together with their different properties suggest they play a different but complementary role in the pathogenic strategy of S. sclerotiorum
Polygalacturonase activity and location in arbuscular mycorrhizal roots of Allium porrum L.
No full textPolygalacturonase activity and location were analysed in leek roots (Allium porrum L.) colonized by Glomus versiforme (Karst.) Berch, an arbuscular mycorrhizal (AM) fungus. Polygalacturonase activity in mycorrhizal roots did not differ quantitatively from that found in nonmycorrhizal roots on all of the four harvesting dates. Fractionation of mycorrhizal root extracts by ion-exchange chromatography showed that expression of polygalacturonase was specific to the mutualistic association. Immunofluorescence and immunogold experiments were carried out to locate the polygalacturonase in mycorrhizal roots using a polyclonal antibody raised against a Fusarium moniliforme endopolygalacturonase. Immunolabelling was observed all over the arbuscules (intracellular fungal structures) but particularly at the interface between the arbuscule and the plant membrane. Since pectins are located in this area, we suggest that polygalacturonase produced during the symbiosis could play a role in plant pectin degradation. © 1995 Springer-Verlag
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
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