1,720,988 research outputs found
Cryptic operon for beta-glucoside metabolism in E. coli K-12: genetic evidence for a regulatory protein. Genetics : 11-25 (1981).
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Studio sulla relazione tra la resistenza alla kanamicina ed il gene “Putative aminoglycoside 3’-phosphotranferase (PAPH) in Sinorhizobium meliloti ceppo 1021
No full textIl ceppo selvatico di Sinorhizobium meliloti 1021 è sensibile alla kanamicina (30 mg/l) anche se Capela et al. (Proc. Natl. Acad. Sci. U.S.A.(2001), 98: 9877-9882), analizzando l’intero genoma, hanno trovato un gene codificante per una “putative aminoglycoside 3'-phosphotransferase” (PAPH), coinvolta nella resistenza ad antibiotici aminoglicosidici quali la kanamicina. Un mutante spontaneo (GM42) kanamicina resistente (200 mg/l) di Sinorhizobium meliloti 1021 è stato caratterizzato da un punto di vista molecolare e fenotipico per analizzare l’attività del gene PAPH.
Il ceppo parentale e GM42 sono stati caratterizzati da un punto di vista microbiologico tramite il MicroLog System Biolog. I risultati mostrano pattern differenti tra il ceppo parentale ed il mutante sulla base della loro capacità di utilizzare o meno fonti di carbonio quali mannitolo o maltosio.
L'amplificazione del gene PAPH tramite PCR ha prodotto un'unica banda sia nel ceppo wild-type 1021 che in GM42 e dal loro sequenziamento non è emersa alcuna differenza nucleotidica. Tuttavia, l’analisi trascrizionale mediante RT-PCR del gene PAPH ha evidenziato differenze tra i due ceppi. Infatti il wild-type non ha prodotto alcun amplicone, mentre GM42 esprime il gene PAPH in diverse condizioni di crescita saggiate.
Sono state condotte ulteriori analisi mediante Western blotting sulle proteine totali del parentale e del ceppo mutante utilizzando l’anticorpo anti-neomicina fosfotransferasi II. GM42 contiene un peptide che immunoreagisce con l’anticorpo utilizzato, tale reattività è assente nel ceppo selvatico. Inoltre tale gene è stato clonato nel vettore di espressione pKK223-3 in E. coli TOP10 e i cloni ottenuti hanno acquisito resistenza alla kanamicina.
Dal confronto dell’espressione genica effettuata mediante DNA-microarrays si evidenzia un’overespressione del gene PAPH e della regione a monte di tale gene nel mutante kanamicina resistente.
Saranno condotte ulteriori indagini per la comprensione dei meccanismi genetici alla base del fenotipo del ceppo mutante GM42. Ciò rappresenterà un considerevole passo in avanti nello studio dei fattori di resistenza delle popolazioni naturali di S. meliloti 1021, aprendo la strada ad un razionale impiego in agricoltura sostenibile
The spliceosomal intron of rolA gene of Agrobacterium rhizogenes is a prokaryotic promoter.
No full textAgrobacterium rhizogenes transfers DNA (T-DNA)from its Ri plasmid to plant cells. All T-DNA genesare expressed in plant cells. The rolA gene is the onlyT-DNA gene that contains an intron in the untranslatedleader region of its mRNA. This paper showsthat (i) the rolA gene is also transcribed in bacteria;(ii) the 85 bp corresponding to the spliceosomalintron drives prokaryotic gene expression in agrobacteria,in free-living rhizobia and in bacteroidswithin root nodules; and (iii) promoter activity isabolished by the deletion of 63 bp from its 50 end andis reduced by mutations changing its sequence nearthe putative 210 region. The expression pattern of achimeric reporter gene shows that, in free-livingbacteria, gene expression takes place during theexponential phase of growth and increases at theonset of the stationary phase. Within root nodules,reporter gene expression occurs in the invasion,nitrogen fixing and senescent zones
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
Use of nodulation pattern, stress tolerance, nodC gene amplification, RAPD-PCR and RFLP-16S rDNA analysis to discriminate genotypes of Rhizobium leguminosarum biovar viciae
No full textTwenty-seven new Rhizobium isolates were obtained from root nodules of wild and crop legumes belonging to the genera Vicia, Lathyrus and Pisum from different agroecological areas in central and southern Italy. A polyphasic approach including phenotypic and genotypic techniques was used to study their diversity and their relationships with other biovars and species of rhizobia. Analysis of symbiotic properties and stress tolerance tests revealed that wild isolates showed a wide spectrum of nodulation and a marked variation in stress tolerance compared with reference strains tested in this study. All rhizobial isolates (except for the isolate CG4 from Galega officinalis) were presumptively identified as Rhizobium leguminosarum biovar viciae both by their symbiotic properties and the specific amplification of the nodC gene. In particular, we found that the nodC gene could be used as a diagnostic molecular marker for strains belonging to the bv. viciae. RFLP-PCR 16S rDNA analysis confirms these results, with the exception of two strains that showed different RFLP-genotypes from those of the reference strains of R. leguminosarum bv. viciae. Analysis of intraspecies relationship among strains by using the RAPD-PCR technique showed a high level of genetic polymorphism, grouping our isolates and reference strains into six different major clusters with a similarity level of 20%. Data from seven parameters of phenotypic and genotypic analyses were evaluated by using principal component analysis which indicated the differences among strains and allowed them to be divided into seven different groups
Preliminary Results on Biotization of Encapsulated Vitro-Derived Propagules of Carrizo Citrange [Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf].
No full textThe encapsulation technology represents a new tool to integrate
micropropagation into the nursery activity. It allows combining the advantages of
zygotic or gamic seeds with those of micropropagation. The synthetic or artificial
seeds have been defined as “artificially encapsulated somatic embryos, shoots or
other tissues which can be used for sowing under in vitro or ex vitro conditions”.
This will be a powerful propagation tool in the nurseryman hands, if the levels of the
synthetic seeds conversion can be increased also in the nurseries, without the asepsis
of in vitro laboratories and with the presence of many parasitic microorganisms, like
bacteria and fungi, responsible for contamination and/or for trophic competition.
This research was carried out in order to apply biotization into the synthetic seed
technology of Carrizo citrange [C. sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.],
one most extensively used citrus rootstock, because of its resistance to the Citrus
tristeza virus (CTV). With this goal, preliminary experiments to set up protocols for
biotization, through the introduction of Plant Growth Promoting Bacteria (PGPB)
into calcium alginate capsules of Carrizo citrange in vitro-derived microcuttings,
were carried out, in order to protect the plantlets from abiotic and biotic factors and
to promote their growth during the first stages of development. Specifically, the
Sinorhizobium meliloti wild type strain 1021 and its derivative RD64, that
synthesizes 80-fold more IAA as compared to the wild type strain, was used to
evaluate their performance in inducing rooting of encapsulated microcuttings
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
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