1,720,983 research outputs found
The non-specific lipid transfer protein N5 of Medicago truncatula is required for efficient nodulation during symbiosis with N-fixing rhizobia
No full textTransgenic adventitious hairy roots carrying a hairpin construct (MtN5hp) for MtN5 silencing are impaired in nodulation, showing a 50% of reduction in the number of nodules compared with inoculated control roots (Pii et al., 2009). This finding indicates that MtN5 is required in the roots for a successful establishment of the symbiotic interaction with S.meliloti. In order to further support the results obtained in transgenic composite plants, we have undertaken the stable genetic transformation of M. truncatula with A. tumefaciens bearing the MtN5hp construct. The analyses carried out on stable-transformed MtN5-silenced plants confirm the role of the lipid transfer protein N5 in root nodule formation
The involvement of Medicago truncatula non-specific lipid transfer protein N5 in the control of rhizobial infection.
No full textCysteine-rich proteins seem to play important regulatory roles in Medicago truncatula/Sinorhizobium meliloti symbiosis. In particular, a large family of nodule-specific cysteine-rich (NCR) peptides is crucial for the differentiation of nitrogen-fixing bacteroids.The Medicago truncatula N5 protein (MtN5) is currently the only reported non-specific lipid transfer protein necessaryfor successful rhizobial symbiosis; in addition, MtN5 shares several characteristics with NCR peptides: a smallsize, a conserved cysteine-rich motif, an N-terminal signal peptide for secretion and antimicrobial activity. UnlikeNCR peptides, MtN5 expression is not restricted to the root nodules and is induced during the early phases of symbiosisin root hairs and nodule primordia.Recently, MtN5 was determined to be involved in the regulation of root tissue invasion; while, it was dispensablefor nodule primordia formation. Here, we discuss the hypothesis that MtN5 participates in linking the progressionof bacterial invasion with restricting the competence of root hairs for infection
Characterization of Mg deficiency in three rootstocks of Vitis vinifera
No full textIl magnesio (Mg2+), nutriente minerale coinvolto in molti processi biochimici, è uno fra i cationi bivalenti più abbondanti all’interno delle cellule vegetali. La sua limitata disponibilità contribuisce al rallentamento dell’attività fotosintetica, impedisce la corretta allocazione dei fotosintetati, provoca clorosi fogliare e una riduzione della biomassa radicale.
In Vitis vinifera, è stato osservato che il contenuto di nutrienti minerali come Mg2+ e K+ del nesto è funzione sia del genotipo del portinnesto che di quello del nesto stesso. D’altra parte, in questa specie, le conoscenze riguardanti i meccanismi fisiologico-molecolari sottesi alla risposta verso la carenza di Mg2+sono molto scarse o addirittura assenti.
Lo scopo di questo lavoro è la caratterizzazione delle risposte fisiologiche e molecolari indotte dalla carenza di Mg2+ in piante di V. vinifera.
Nella prima fase del lavoro sperimentale sono state utilizzate barbatelle di V. vinifera cv. Corvina innestate su portinnesti (SO4, 41B e 1103P) con una diversa tolleranza alla carenza di Mg2+. Le barbatelle sono state allevate in coltura idroponica e sottoposte a deprivazione di Mg2+ per 15 settimane. I risultati hanno evidenziato che il portinnesto può influenzare la capacità del nesto di accumulare il Mg2+: la concentrazione di Mg2+ nei tessuti delle barbatelle innestate su 1103P, il portinnesto ritenuto più resistente alla carenza di Mg2+ sulla base di osservazioni di campo, era infatti quasi doppia rispetto a quella delle altre piante. La sintomatologia della carenza di Mg2+ è stata caratterizzata mediante la registrazione di alcuni parametri fisiologici, quali il contenuto di clorofilla (indice SPAD), la produzione di biomassa e altri parametri di crescita degli organi ipogei ed epigei. Le femminelle del nesto mostravano una sintomatologia da carenza di Mg2+più severa rispetto al tralcio principale. Anche lo studio dei parametri biochimici, in particolare la concentrazione e la distribuzione dei fotosintetati, ha messo in luce un accumulo di zuccheri nelle foglie basali delle femminelle, a conferma della più intensa sintomatologia osservata.
In considerazione delle difficoltà pratiche che si incontrano nell’allevamento in soluzione idroponica di materiale sperimentale di dimensioni ragguardevoli quale quello costituito dalle barbatelle, e al fine di poter studiare la carenza di Mg2+ indipendentemente dall’interazione tra nesto e portinnesto, è stato sviluppato un nuovo sistema sperimentale basato sull’utilizzo di microtalee del solo portinnesto. Tale sistema sarà anche impiegato per lo studio della regolazione dell’espressione dei geni coinvolti nei processi di risposta alla carenza di Mg2+
Effect of increased IAA synthesis in root nodules of Medicago plants
No full textIn plants auxin modulates diverse processes such as tropic response to light and gravity, general root and shoot growth and vascular development. IAA (indol-3-acetic acid) is produced largely in shoot apex. Auxin is transported basipetally in shoots, while both acropetal (in the central cylinder) and basipetal (via epidermaland cortical cells) transport occur in roots [4]. Most Rhizobacteria synthesize IAA, and in symbiotic Rhizobia have been identified different auxin biosyntheticpathways. It has been proposed that IAA plays a role in nodule formation, and it has been also demonstrated that nodulated roots have a phytormone content higherthan root tissue [1]. Sinorhizobium meliloti induces nodule formation in Medicago species; S. meliloti 1021 has been engineered by introducing promintron-iaaM-tms2gene construct (S. meliloti 1021 IAA), which increases auxin content in the nodules
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
Nodulation of determinate and indeterminate legumes by Rhizobia expressing an auxin-synthesising chimeric operon
No full textLeguminous plants can establish mutualistic symbiosis with soil bacteria called Rhizobia; the interaction leads to the development of nitrogen-fixing root nodules. The formation of root nodules involves the activities of endogenous phytohormone, such as ethylene, cytokinin and auxin (IAA). The latter seems to have a different role in signaling for the initiation of determinate and indeterminate nodules. Sinorhizobium meliloti induces indeterminate nodules in Medicago species, while Rhizobium leguminosarum is able to form determinate nodules in Phaseolus vulgaris. We have engineered S. meliloti and R. leguminosarum by introducing an auxin-synthesising chimeric operon generating AUX strains, which allows to increase the amount of IAA produced by Rhizobia within bacteroids in the nodules. The aim of our research is to compare the effects of increased levels of IAA in bacteroids on nodulation in determinate and indeterminate legumes. Our results show two different behaviours: Medicago species develop an higher number of nodules when inoculated with AUX strain, while P. vulgaris, nodulated by Aux strain or wild type Rhizobia, forms the same number of root nodules
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
Functional Characterization of a new Lipid Transfer Protein With Antimicrobial Properties From Medicago truncatula
No full textNon specific lipid transfer proteins form a multigenic protein family in plants. They are able to bind in vitro different lipids but their function in vivo remains speculative. They have been suggested to participate to many aspects of plant physiology and cell biology, including assembly of extracellular hydrophobic polymers and involvement in stress and pathogen responses. To understand whether MtN5, a new LTP2 identified in Medicago truncatula roots, plays a possible role in the plant protection function, we investigated its antifungal and antibacterial properties. A cDNA sequence encoding the protein, without the signal peptide, was cloned in a prokaryotic expression system. The purified recombinant protein has been characterized for its lipid binding properties and for its in vitro antimicrobial properties. The results showed that the recombinant MtN5 is able to bind lipids, similarly to other members of the LTP protein family and possesses a selective action against specific pathogens, potentially due to interactions with microbe specific membrane structures
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