1,720,958 research outputs found
β-glucuronidases in plants.
Full text linkIn the last decade, the interest for the presence and role of endogenous GUS in plants increased, being previously limited to the use of GUS from E. coli as a reporter gene. Three different GUS genes have been identified in A. thaliana and different roles have been suggested, mainly associated to plant cell wall remodelling and to the regulation of the presence in the active form of molecules with regulative functions.
This thesis investigated several aspects: A) artefacts in histochemical GUS detection, B) role of GUS in pollen tube germination and growth, C) GUS expression in N. tabacum and A. thaliana, D) identification of GUS genes in N. tabcum and their phylogenetic analysis in angiosperms.
A) Histochemical detection of E.coli GUS activity in transformed plants can be impaired by the presence of GUS inhibitors and by the solubility of an intermediate reaction product formed when X-glu is used as substrate. The expression of LAT52 has been revised.
B) The use of saccharolattone, a GUS inhibitor, suggests that GUS is involved in pollen tube germination and growth.
C) GUS expression was observed in all organs of N. tabacum and A. thaliana.
Expression studies, in collaboration with researchers of Calabria University, have been performed in Arabidopsis, by in situ mRNA hybridization: GUS3 is specifically expressed in border like cells and probably it is involved in their detachment from root tip; GUS1 and GUS2 are expressed in the root cup meristem, resulting perhaps involved in regulation of the mitotic cycle.
D) In N. tabacum GUS2 was completely sequenced and one GUS1 and two GUS3 have been partially sequenced. By bioinformatics analysis, GUS genes have been identified in other angiosperms species and a phylogenetic analysis have been conducted
Platinum, Palladium and Rhodium deposition to the Prunus laurus cerasus leaf surface as an indicator of the vehicular traffic pollution in the city of Varese area. An easy and reliable method to detect PGEs released from automobile catalytic converters
No full textBackground, aim, and scope The widespread use of some Platinum Group Elements (PGE) as catalysts to minimize emission of pollutants from combustion engines produced a constantly growing increase of the concentration of these elements in the environment; their potential toxicological properties explain the increasing interest in routine easy monitoring. We have found that leaves of Prunus laurus cerasus are efficient collectors of particulate with a dimension < 60-80 μm, and a simple and reliable procedure was developed to reveal traces of platinum, palladium and rhodium released from automotive catalysts. The analysis of the dust deposited on the foliage is a direct indicator of traffic pollution.
Materials and methods Leaves of prunus laurus cerasus were washed by sonication in a mixture of water and 2 propanol and the washings, to be discarded, were separated by centrifugation to yield typically 0.05-1.2 g of dust that, after mineralization, were directly submitted to Atomic Absorption analysis.
Results Comparison of the 2007 and 2004-5 results showed a dramatic reduction of the platinum levels and revealed that palladium is now the main component of this traffic related pollution.
Discussion The results are consistent with the increasing diffusion of cars with a diesel engine whose catalysts are made up of Pt and/or Pd alone, and gives a significant insight into the recent evolution in catalyst design that replaces platinum for palladium.
Conclusion The proposed analytical procedure is simple, with short preparation times, and greatly reduces matrix effects so that atomic absorption spectroscopy can easily detect the three noble metals at the ng/g level in the dust.
Recommendation and perspectives The results clearly show that Pd concentrations have increased over time, and must be cause of concern
Analysis of AtGUS1 and AtGUS2 in Arabidopsis root apex by a highly sensitive TSA-MISH method
Full text linkA new highly sensitive whole-mount in situ hybridization method, based on tyramide signal amplification (TSA-MISH) was developed and a combined GFP detection and TSA-MISH procedure was applied for the first time in plants, to precisely define the spatial pattern of AtGUS1 and AtGUS2 expression in the root apex. β-glucuronidases (GUSs) belonging to the glycosyl hydrolases (GHs) 79 family, are widely distributed in plants, but their functional role has not yet been fully investigated. In the model system Arabidopsis Thaliana, three different AtGUS genes have been identified which encode proteins with putative different fates. Endogenous GUS expression has been detected in different organs and tissues, but the cyto-histological domains of gene expression remain unclear. The results here reported show co-expression of AtGUS1 and AtGUS2 in different functional zones of the root apex (the cap central zone, the root cap meristem, the staminal cell niche and the cortical cell layers of the proximal meristem), while AtGUS2 is exclusively expressed in the cap peripheral layer and in the epidermis in the elongation zone. Interestingly, both genes are not expressed in the stelar portion of the proximal meristem. A spatial (cortex vs. stele) and temporal (proximal meristem vs. transition zone) regulation of AtGUS1 and AtGUS2 expression is therefore active in the root apex. This expression pattern, although globally consistent with the involvement of GUS activity in both cell proliferation and elongation, clearly indicates that AtGUS1 and AtGUS2 could control distinct downstream process depending on the developmental context and the interaction with other players of root growth control. In the future, the newly developed approaches may well be very useful to dissect such interactions
Palladium uptake by Pisum sativum: partitioning and effects on growth and reproduction
No full textEnvironmental palladium levels are increasing because of anthropogenic activities. The considerable mobility of the metal, due to solubilisation phenomena, and its known bioavailability may indicate interactions with higher organisms. The aim of the study was to determine the Pd uptake and distribution in the various organs of the higher plant Pisum sativum and the metal-induced effects on its growth and reproduction. P. sativum was grown in vermiculite with a modified Hoagland's solution of nutrients in the presence of Pd at concentrations ranging 0.10-25 mg/L. After 8-10 weeks in a controlled environment room, plants were harvested and dissected to isolate the roots, stems, leaves, pods and peas. The samples were analysed for Pd content using AAS and SEM-EDX. P. sativum absorbed Pd, supplied as K2PdCl4, beginning at seed germination and continuing throughout its life. Minimal doses (0.10-1.0 mg Pd/L) severely inhibited pea reproductive processes while showing a peculiar hormetic effect on root development. Pd concentrations ≥1 mg/L induced developmental delay, with late growth resumption, increased leaf biomass (up to 25 %) and a 15-20 % reduction of root mass. Unsuccessful repeated blossoming efforts led to misshapen pods and no seed production. Photosynthesis was also disrupted. The absorbed Pd (ca. 0.5 % of the supplied metal) was primarily fixed in the root, specifically in the cortex, reaching concentrations up to 200 μg/g. The metal moved through the stem (up to 1 μg/g) to the leaves (2 μg/g) and pods (0.3 μg/g). The presence of Pd in the pea fruits, together with established evidence of environmental Pd accumulation and bioavailability, suggests possible contamination of food plants and propagation in the food chain and must be the cause for concern
Espressione dei geni GUS e UGT85A in Arabidopsis thaliana
No full textLe β-glucuronidasi (GUS) sono enzimi che catalizzano l’idrolisi del legame glicosidico fra l’acido β-glucuronico e altre molecole e sono suddivise in due famiglie: glicosil-idrolasi 2 e glicosil-idrolasi 79. Le β-glucuronidasi della famiglia 2, alle quali appartiene il GUS di E. coli largamente usato come gene reporter nei vegetali, sono note in un grande range di organismi, ma sembrano essere assenti nelle piante, nelle quali l’attività GUS endogena sembra associata a β-glucuronidasi della famiglia 79 (Eparanasi) (1).
In Arabidpopsis thaliana sono stati identificati e parzialmente caratterizzati tre diversi geni GUS (AtGUS1, AtGUS2 e AtGUS3), dei quali AtGUS1 e AtGUS2 mostrano elevata omologia.
A parte funzioni specifiche (2),coinvolgimento delle β-glucuronidasi è stato proposto nel processo di accrescimento cellulare per distensione e, in particolare, nell’allungamento dei peli radicali (3). E’ stato, inoltre, ipotizzato che β-glucuronidasi, agendo in coordinazione con glucuronisiltrasferasi (UGT) del gruppo 85A, siano responsabili della regolazione del ciclo cellulare (4,5). Uno studio più recente tuttavia ha messo in parte in discussione quanto emerso in precedenza riportando che nelle radici di plantule di Arabidopsis thaliana non è presente attività β-glucuronidasica (6).
In questo lavoro si è voluto approfondire lo studio dell’espressione dei geni GUS e UGT in Arabidopsis. Verifiche preliminari effettuate con PCR semiquantitativa hanno mostrato che, nonostante il gene AtGUS2 risulti espresso in modo più rilevante rispetto a AtGUS1 e AtGUS3, tutti e tre i geni AtGUS sono espressi, sia pure differenzialmente, in tutti gli organi della pianta. I geni AtUGT85A mostranoun pattern di espressione più differenziato rispetto ai geni AtGUS. AtUGT85A1, AtUGT85A2 e AtUGT85A4 risultano differenzialmente espressi nei vari organi della pianta, mentre AtUGT85A3 e UGT85A7 mostrano un’espressione organo specifica che coinvolge fiore e foglia
Utilizzando la tecnica di ibridazione in situ con sonde multiple recentemente messa a punto su campioni vegetali (7), l’espressione dei geni GUS è stata studiata anche a livello tissutale. A livello radicale , il pattern di espressione dei tre geni analizzati appare chiaramente differenziato: AtGUS1 e AtGUS2 sono espressi nell’epidermide, nella zona corticale e nella cuffia, mentre l’espressione di AtGUS3 è limitata all’epidermide. Sono in corso le analisi relative agli altri organi della pianta e, in particolare, fiore e polline. Analogo approccio verrà esteso ai geni AtUGT85 al fine di verificarne l’overlapping o meno con i domini istologici di espressione dei geni GUS e definirne eventuali correlazioni
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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