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Interazioni molecolari tra l’omeostasi del ferro e del molibdeno in mitocondri di Cucumis sativus L
No full textIl molibdeno (Mo) è un micronutriente essenziale in quasi tutti gli organismi comprese le piante [1]. Il Mo, sotto forma di molibdato, è complessato con un pterina per formare il cofattore-molibdeno (Moco), che è biologicamente funzionale e che viene inserito nei cosiddetti molibdo-enzimi. Il molibdeno è quindi coinvolto in processi metabolici essenziali o importanti come assimilazione dell'azoto, sintesi dell’acido abscissico (ABA) e catabolismo delle purine. Un’alterazione del metabolismo del Mo ha effetti drammatici sulla crescita e sulla resa della pianta.
Recentemente, è stato evidenziato come il metabolismo del Mo interagisca fortemente con quello del ferro (Fe) [2]. Scopo di questo lavoro è quello di indagare la mutua regolazione dei meccanismi fondamentali alla base dell’assorbimento e della compartimentazione subcellulare di Mo e Fe in piante di cetriolo (Cucumis sativus) cresciute in diverse condizioni nutrizionali di Mo e di Fe.
Piante di cetriolo sono state allevate nelle seguenti condizioni: controllo (+Fe+Mo), carenza di Fe (-Fe+Mo), carenza di Mo (+Fe-Mo) o entrambe le carenze (-Fe-Mo).
Analisi ionomiche condotte tramite ICP-MS dei tessuti vegetali e di mitocondri purificati dalle radici hanno permesso di osservare come le carenze di Fe e di Mo determinino forti variazioni nel contenuto dei vari micro e macro elementi sia a livello dell'intera pianta che a livello subcellulare. Inoltre è stata osservata una variazione della distribuzione mitocondriale del Fe e del Mo in piante +Fe-Mo e –Fe+Mo. Attraverso un’analisi proteomica sono state valutate le alterazioni indotte dalle carenze di tali nutrienti a livello mitocondriale. Sono state identificate oltre cento proteine i cui livelli di espressione sono significativamente alterati in almeno uno dei trattementi nutrizionali utilizzati. I dati preliminari ottenuti suggeriscono una significativa intarazione tra il metabolismo del Fe e del Mo a livello mitocondriale.
[1]Bittner and Mendel (2010) Springer-Verlag, Plant Cell Monogr 17:119-143.
[2]Bittner (2014) Front. Plant Sci. 5:28
Towards the unveiling of the molecular interactions connecting subcellular Molybdenum and Iron homeostasis
No full textMolybdenum (Mo) is a transition metal and micronutrient, which is essentially required in the form of molybdate by nearly all organisms including plants [1]. Molybdate is complexed by a Mo-binding pterin to form the biologically functional molybdenum cofactor (Moco), which is inserted into the so-called molybdo-enzymes. Mo is therefore involved in essential or important metabolic processes such as nitrogen assimilation, ABA synthesis, and purine catabolism and impaired Mo metabolism has dramatic effects on plant growth and yield.
Most recently, a significant crosstalk between the metabolisms of iron (Fe) and Mo has been exposed [2]. Our goal is to investigate the mutual regulation of basic mechanisms underlying uptake and subcellular compartmentalization of Mo and Fe in Cucumis sativus (cucumber) plants grown under different Mo and Fe nutritional conditions.
For that, cucumber plants have been grown in the following conditions: control, Fe deficiency, Mo deficiency or both deficiencies. The ionomes of whole tissues (root and leaves) as well as of root mitochondria have been profiled. Moreover, a high-throughput proteomic approach named “MudPIT” (Multidimentional Protein Identification Technology) [3], has been applied to identify novel proteins involved in Mo and/or Fe metabolism (such as molybdate storage proteins) and to focus on changes occurring in chloroplasts and mitochondria under the nutritional stresses indicated above.
Fe content decreases in Fe deficient plants roots and Mo content decreases in Mo deficient plants roots. In addition, Fe content decreases in mitochondria purified from Fe-deficient roots and Mo content decreases in mitochondria purified from Mo-deficient roots, indicating that the above described treatments are effective in modifying Fe and Mo homeostasis at whole plant level and at the subcellular level. Alteration of Mo nutritional supply does not dramatically affect physiological parameters (chlorophyll content, O2 evolution, O2 consumption) relative to what has been observed under Fe deficiency in ten-days-old cucumber plants. Yet, striking changes are observed at protein and ion levels in plants grown under these nutritional stress conditions. Such results indicate that our experimental set-up is appropriate for uncovering not only early responses to Mo deficiency but also Mo and Fe molecular interactions. Most interesting, we observed a perturbation of mitochondrial Fe distribution under Mo deficiency. Furthermore, we identified more than hundred proteins whose expression levels were significantly altered in at least one of the reported nutritional stresses.
Remarkably, among the various proteins, MudPIT also identified the Fe-storage and Fe-responsive protein ferritin only in mitochondria purified from control roots. This result nicely supports what we recently demonstrated in [4], namely that ferritin is functional in root mitochondria of Fe-sufficient cucumber plants, albeit at low levels relative to the accumulation observed under Fe excess [4]. These findings thus confirm that our proteomics approach is truly sensitive and can identify low-abundant proteins. Results obtained will be commented and potentiality of such approach will be illustrated.
[1]Bittner and Mendel (2010) Springer-Verlag, Plant Cell Monogr 17:119-143.
[2]Bittner (2014) Front. Plant Sci. 5:28.
[3] Wolters et al (2001)Anal Chem. 73:5683-5690.
[4] Vigani et al (2013) Front. Plant Sci 316:1-8
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Analysis of molecular response to selenium supplementation by multidimensional protein identification technology
No full textThe anticancer effects of the trace element selenium have been shown in clinical, preclinical and laboratory studies. Despite mechanisms of action are not completely understood, the tuning of cellular redox state by selenium seems to be of particular relevance.
The aim of this work is to study the response to selenium supplementation in a prostate cancer cell line (LNCaP) by comparing protein expression profiles in cells grown without (control) and with (Se supplemented) selenium added to the medium. Selenium supplementation is achieved by growing cells in 100 nM Sodium Selenite for three days. The measurement of selenium peroxidase activities is used as the marker of successful supplementation.
Protein expression profiles study was performed by combination of two dimensional liquid chromatography separation with mass spectrometry analysis of chromatographic fractions.
Solubilized proteins from pelleted cells are first separated in a two dimensional liquid chromatography system (chromatofocusing and reverse phase chromatography). The profiles of all the chromatographic separations of the two samples are compared by means of a program (DeltaVue) and a differential map expression is generated. Consistent peaks which are reproducibly differently expressed (at least a 100% difference) are analyzed with mass spectrometry (MALDI-TOF and ESI-MS/MS). We obtained high confidence protein identification with different search engine (Mascot and Protein Prospector for MALDI-MS and SEQUEST for ESI-MS) for most of differently expressed chromatographic peaks. This multidimensional protein identification system allows us to identify proteins with about 10-90KDa molecular weight
A novel approach to investigate a rare Frontotemporal Disorder: proteomic studies about Nasu-Hakola Disease
No full textFrontotemporal dementias (FTD) include a large spectrum of pathologies based on different triggers. Among the FTD related to genetic causes and behavioral disorders (bvFTD), a rare recessively inherited systemic disorder named Nasu-Hakola Disease (NHD) is worthy of note. It is phenotypically characterized by simultaneous impairment of nervous and skeletal systems and genetically related to a structural defect of the two genes DAP12 and TREM2. These genes encode for different subunits of the membrane receptor signaling complex and are expressed by cells of both systems involved. To date, the diagnosis of NHD is carried out by genetic or psychological tests only; no biochemical/molecular studies being available to obtain an early diagnosis or a follow-up of the NHD progression.
In the present study we used MudPIT (Multidimensional Protein Identification Technology) approach for the characterization of Lymphoblastoid cells from NHD patients and healthy controls.
Aim of this research was to obtain a more complete picture about the mechanisms involved into NHD onset and to evaluate the presence of possible blood biomarkers of this pathology.
Specifically, two NHD patients (DS), four healthy carriers (HC) and one healthy subject (HS) belonging to the same Italian family have been submitted to blood withdrawal to isolate and
immortalize the B-Lymphocytes. MudPIT allowed the identification of more than 3000 distinct proteins, a number 100-fold higher than that of proteins identified by gel electrophoresis (2-DE)
[Giuliano et al. PLoS One 2014; 9]. The comparison of protein profiles from DS, HC and HS groups by means of MAProMa software showed that 10% of identified proteins was peculiar of each
group. In addition, network analysis of proteomics data evidenced the disease-related pathways, such as energy metabolism, including glucose pathway.
This work represents a proof of principle for characterizing dysregulated proteins and related metabolic pathways involved in functional alterations of this pathology
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
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