1,720,969 research outputs found
Distinct Effects of p19 RNA Silencing Suppressor on Small RNA Mediated Pathways in Plants
No full textRNA silencing is one of the main defense mechanisms employed by plants to fight viruses. In change, viruses have evolved silencing suppressor proteins to neutralize antiviral silencing. Since the endogenous and antiviral functions of RNA silencing pathway rely on common components, it was suggested that viral suppressors interfere with endogenous silencing pathway contributing to viral symptom development. In this work, we aimed to understand the effects of the tombusviral p19 suppressor on endogenous and antiviral silencing during genuine virus infection. We showed that ectopically expressed p19 sequesters endogenous small RNAs (sRNAs) in the absence, but not in the presence of virus infection. Our presented data question the generalized model in which the sequestration of endogenous sRNAs by the viral suppressor contributes to the viral symptom development. We further showed that p19 preferentially binds the perfectly paired ds-viral small interfering RNAs (vsiRNAs) but does not select based on their sequence or the type of the 5’ nucleotide. Finally, co-immunoprecipitation of sRNAs with AGO1 or AGO2 from virus-infected plants revealed that p19 specifically impairs vsiRNA loading into AGO1 but not AGO2. Our findings, coupled with the fact that p19-expressing wild type Cymbidium ringspot virus (CymRSV) overcomes the Nicotiana benthamiana silencing based defense killing the host, suggest that AGO1 is the main effector of antiviral silencing in this host-virus combination. © 2016 Kontra et al
Il silenziamento dell’RNA nell’interazione pianta-virus
No full textPrefazione Il testo di Patologia Vegetale Molecolare, scritto da più di 70 autori e coordina- to da Massimo Reverberi, Lorenzo Covarelli, Michelina Ruocco e Luca Sella, rappresenta un affresco attuale delle conoscenze sull’interazione pianta-pato- geno, sulla biologia dei principali patogeni vegetali, sugli approcci sostenibili alla lotta contro le fitopatie, fino agli aspetti diagnostici molecolari più inno- vativi. Il testo si presenta diviso in 6 sezioni, in cui le prime 3 approfondiscono rispettivamente aspetti molecolari e cellulari di virus e viroidi (sezione 1), fi- toplasmi e batteri (sezione 2), oomiceti e funghi (sezione 3), mentre la quarta sezione è interamente dedicata alle interazioni molecolari pianta-patogeno e ambiente, con un focus particolare sulle principali reazioni difensive del- la pianta, locali e sistemiche, sia ai patogeni che ai principali stress abiotici. Nella quinta sezione si affrontano i temi più legati alla difesa sostenibile e allo sviluppo di innovazione nel controllo delle fitopatie (es. genome editing), mentre la sesta riporta un’ampia rassegna delle metodologie più recenti per la diagnosi delle principali fitopatie. Il libro è un testo unico nel suo genere, composto da 37 capitoli, ciascuno dei quali è stato concepito e scritto dai principali esperti dello specifico am- bito trattato, e cerca di rappresentare al meglio tutti gli aspetti della ricerca italiana nel settore dell’interazione pianta-patogeno ed in generale della Pato- logia Vegeta
Transcriptomics of tomato plants infected with TYLCSV or expressing the central TYLCSV Rep protein domain uncover changes impacting pathogen response and senescence
No full textTo establish a successful infection viruses need to overcome plant innate immune responses and redirect host gene expression for their multiplication and diffusion. Tomato yellow leaf curl Sardinia virus (TYLCSV) is a geminivirus, which causes significant economic losses in tomato. The multifunctional replication associated geminivirus protein (Rep) has an important role during viral infection. In particular, the Rep central domain spanning from aa 120 to 180 is known to interact with viral and host factors. In this study, we used long serial analysis of gene expression to analyse the transcriptional profiles of transgenic tomato plants expressing the first 210 amino acids of TYLCSV Rep (Rep210) and TYLCSV-infected wild-type tomato plants (Wt-Ty). Also, we compared these profiles with those of transgenic Rep130 tomatoes. Comparison of Wt-Ty and Rep210 libraries with the wild-type one identified 118 and 203 differentially expressed genes (DEGs), respectively. Importantly, 55% of Wt-Ty DEGs were in common with Rep210, and no ones showed opposite expression. Conversely, a negligible overlap was found between Rep130 DEGs and Wt-Ty and Rep210 ones. TYLCSV- and Rep210-repressed genes, but not induced ones, overlapped with the leaf senescence process. Interestingly, TYLCSV upregulates expression of genes involved in the negative regulation of programmed cell death (PCD), several of which were also regulated by the abscisic acid. Rep210 upregulated genes related to defence response, immune system processes and negative regulation of PCD. Collectively, our results support a model in which the Rep central domain has a pivotal role in redirecting host plant gene expression. © 2016 Elsevier Masson SAS
Identification, intra- and inter-laboratory validation of a diagnostic protocol for ‘Candidatus Liberibacter solanacearum’ in carrot seeds
No full text‘Candidatus Liberibacter solanacearum’ (CaLsol) is a phloem-limited, unculturable, Gram-negative bacterium associated with emerging diseases in crops of the Solanaceae and Apiaceae families. As it has been shown to be seed-transmitted in carrot, emergency measures for exportation require carrot seed to be heat-treated or tested by PCR and found CaLsol free. Therefore, the identification and harmonization of a protocol for CaLsol diagnosis in carrot seed are becoming of socio-economic priority. We initially set up an improved DNA extraction method for Apiaceae seeds and identified, among the widely used PCR tests to detect and identify CaLsol, the real-time PCR developed by Li et al. (Journal of Microbiological Methods, 78(1), 59–65, 2009) and the end-point PCR by Ravindran et al. (Plant Disease, 95(12), 1542–1546, 2011) to be the most sensitive ones. The two PCR methods were initially intra-laboratory validated followed by a “Test Performance Study” involving 11 Italian laboratories that received both the samples and the material necessary to carry out the experiments. The results indicated that the improved DNA extraction method was robust and that the real-time PCR showed the highest analytical sensitivity in the intra-laboratory validation tests. Similarly, the real-time PCR outperformed the end-point PCR in the inter-laboratory comparison assay showing a higher percentage of accuracy, accordance, and concordance. The overall obtained data could be used for the appropriate application of phytosanitary measures against CaLsol
VIGS for functional analysing potential candidate tomato genes involved in TYLCSV susceptibility
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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
‐terminal domain of the replication‐associated protein show transcriptional changes resembling stress‐related responses
No full textThe N-terminal domain (amino acids 1-130) of the replication-associated protein (Rep130) of Tomato yellow leaf curl Sardinia virus (TYLCSV) retains the ability of full-length Rep to localize to the nucleus and to down-regulate C1 transcription when ectopically expressed in plants, both functions being required to inhibit homologous viral replication. In this study, we analysed the effect of Rep130 expression on virus resistance and the plant transcriptome in the natural and agronomically important host species of TYLCSV, Solanum lycopersicum. Tomato plants accumulating high levels of Rep130 were generated and proved to be resistant to TYLCSV. Using an invitro assay, we showed that plant-expressed Rep130 also retains the catalytic activity of Rep, thus supporting the notion that this protein domain is fully functional. Interestingly, Rep130-expressing tomatoes were characterized by an altered transcriptional profile resembling stress-related responses. Notably, the serine-type protease inhibitor (Ser-PI) category was over-represented among the 20 up-regulated genes. The involvement of Rep130 in the alteration of host mRNA steady-state levels was confirmed using a distinct set of virus-resistant transgenic tomato plants expressing the same TYLCSV Rep130, but from a different, synthetic, gene. Eight genes were found to be up-regulated in both types of transgenic tomato and two encoded Ser-PIs. Four of these eight genes were also up-regulated in TYLCSV-infected wild-type tomato plants. Implications with regard to the ability of this Rep domain to interfere with viral infections and to alter the host transcriptome are discussed. � 2013 BSPP AND JOHN WILEY & SONS LTD
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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