74 research outputs found
Presenza di un ceppo necrogenico di Watermelon mosaic virus in colture di melone in Sicilia.
No full textIn the spring of 2011, a necrotic disease was observed in yellow melon plants grown in western Sicily (Italy). An infection of Watermelon mosaic virus (WMV) was detected and transmitted to herbaceous hosts, using infected tissues collected from young and mature leaves and from symptomatic fruits. Analyses based on molecular hybridization and observations with the electron microscope excluded the presence of Zucchini yellow mosaic virus, Papaya ringspot virus and of viruses with isometric particles. Although based on preliminary evidences, the results of this study suggest that a necrogenic isolate of WMV for which the name of WMV-Si is proposed, was involved in the severe disease observed on yellow melon plants
exploits pit membranes of susceptible olive cultivars to spread systemically in the xylem
Get PDFXylella fastidiosa subspecies pauca strain De Donno (XfDD) ST53 is the causal agent of olive quick decline syndrome, a severe disease first described in Apulia, Italy. Although the two local cultivars Cellina di Nardo and Ogliarola Salentina showed high susceptibility, traits of resistance to the bacterium were found in the cultivar Leccino. Previous studies in field-grown olives suggested that vascular occlusions and anatomophysiological properties of the different cultivars played a role in the olive response to XfDD. The present investigation reports observations at the early stage of the infection on artificially inoculated olives. Electron microscope studies showed that XfDD exploits the pit membranes (PMs) of the susceptible cultivar Cellina di Nardo to spread systemically. In this cultivar, PMs were degraded upon XfDD infection, suggesting activity of bacterial cell wall-degrading enzymes. Moreover, occluded vessels contained an amorphous electrondense matrix resembling gum. Conversely, in Leccino, occluded vessels were mainly filled by callose-like granules that tightly entrapped XfDD cells. In addition, PMs from Leccino had a compact undegraded structure that was not permeable to XfDD. Our study suggests that exploitation of PMs is a key event in the infection process of X. fastidiosa subsp. pauca ST53 in susceptible olive cultivars
Study of the Effect of Water Pressure on Plasma and Cavitation Bubble Induced by Pulsed Laser Ablation in Liquid of Silver and Missed Variations of Observable Nanoparticle Features
No full textIn this work the effects of the pressure between 1–150 Bar on pulsed laser ablation in liquids (PLAL) during the production of silver nanoparticles (AgNPs) in water was investigated. The produced NPs are the results of two different well-known stages which are the plasma and the bubble evolution occurring until the generated material is released into the solution. The main aim of this work is to show which roles is played by the variation of water pressure on the laser induced plasma and the cavitation bubble dynamics during the NPs formation. Their implication on the comprehension of the as-produced NPs formation mechanisms is treated. The typical timescales of the different stages occurring in water at different pressures have been studied by optical emission spectroscopy (OES), imaging and shadowgraph experiments. Finally surface plasmon resonance (SPR) spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS) and scanning electron microscopy (SEM) for characterization of the material released in solution, have been used
Synthesis and biophysical evaluation of arylhydrazono-1H-2-indolinones as beta-amyloid aggregation inhibitors
No full textA series of isatin-3-arylhydrazones were synthesized and evaluated in vitro as inhibitors of Ab1e40
aggregation using a thioflavin T fluorescence method. An exploration of the effects on Ab1e40 aggregation
of a number of diverse substituents at phenylhydrazone group and 5,6- positions of the indolinone
nucleus led us to single out some new anti-aggregating compounds with IC50 values in the low micromolar
range. The most active compounds carry methoxy- or hydroxy- substituents in the indolinone
5,6-positions and lipophilic groups such as iPr and Cl at 40- and 30-position, respectively, of the phenylhydrazone
moiety. Two derivatives are noteworthy, namely 18 (IC50 1⁄4 0.4 mM) and 42 (IC50 1⁄4 1.1 mM).
The in vitro effects of the highly active, water soluble, compound 42 on the temporal evolution of Ab1e40
fibrils formation were further investigated by circular dichroism spectroscopy, transmission electron
microscopy and dynamic light scattering studies, which clearly showed that this compound delayed and
lowered the amyloid fibril formation
Basidiomycetes are particularly sensitive to bacterial volatile compounds: mechanistic insight into the case study of Pseudomonas protegens volatilome against Heterobasidion abietinum
No full textVolatile organic compounds (VOCs) play an important role in the communication among organisms, including plants, beneficial or pathogenic microbes, and pests. In vitro, we observed that the growth of seven out of eight Basidiomycete species tested was inhibited by the VOCs of the biocontrol agent Pseudomonas protegens strain CHA0. In the Ascomycota phylum, only some species were sensitive (e.g., Sclerotinia sclerotiorum, Botrytis cinerea, etc.) but others were resistant (e.g., Fusarium oxysporum f. sp. cubense, Verticillium dahliae, etc.). We further discovered that CHA0 as well as other ten beneficial or phytopathogenic bacterial strains were all able to inhibit Heterobasidion abietinum, which was used in this research as a model species. Moreover, such an inhibition occurred only when bacteria grew on media containing digested proteins like peptone or tryptone (e.g., Luria-Bertani agar or LBA). Also, the inhibition co-occurred with a pH increase of the agar medium where the fungus grew. Therefore, biogenic ammonia originating from protein degradation by bacteria was hypothesized to play a major role in fungus inhibition. Indeed, when tested as a synthetic compound, it was highly toxic to H. abietinum (effective concentration 50% or EC50 = 1.18 M; minimum inhibitory concentration or MIC = 2.14 M). Using gas chromatography coupled to mass spectrometry (GC/MS), eight VOCs were found specifically emitted by CHA0 grown on LBA compared to the bacterium grown on potato dextrose agar (PDA). Among them, two compounds were even more toxic than ammonia against H. abietinum: dimethyl trisulfide had EC50 = 0.02 M and MIC = 0.2 M, and 2-ethylhexanol had EC50 = 0.33 M and MIC = 0.77 M. The fungus growth inhibition was the result of severe cellular and sub-cellular alterations of hyphae occurring as early as 15 min of exposure to VOCs, as evidenced by transmission and scanning electron microscopy observations. Transcriptome reprogramming of H. abietinum induced by CHA0’s VOCs pointed out that detrimental effects occurred on ribosomes and protein synthesis while the cells tried to react by activating defense mechanisms, which required a lot of energy diverted from the growth and development (fitness cost)
Cucumber mosaic virus Is Unable to Self-Assemble in Tobacco Plants When Transmitted by Seed
Get PDFCucumber mosaic virus (CMV), which has great impact on agronomic production worldwide, is both aphid and seed transmitted. Although the mechanisms of aphid transmission have been widely studied, those underlying the ability of CMV to survive and remain infectious during the passage from one generation to the next through the seeds are still to be clarified. Moreover, the viral determinants of seed transmission rate are poorly understood. Three viral genotypes produced from same RNA 1 and 2 components of CMV-Fny but differing in RNA 3 (the wild type CMV-Fny, a pseudorecombinant CMV-Fny/CMV-S and a chimeric CMV previously obtained by our group, named F, FS and CS, respectively) were propagated in Nicotiana tabacum cv Xanthi plants in order to assess differences in tobacco seed transmission rate and persistence through plant generations in the absence of aphid transmission. Seed-growth tests revealed CMV infection in the embryos, but not in the integuments. Seedlings from seed-growth tests showed the presence of all considered viruses but at different rates: from 4% (F, FS) to 16% (CS). Electron microscopy revealed absence (CS) of viral particles or virions without the typical central hole (F and FS). In agreement, structural characteristics of purified CMV particles, assessed by circular dichroism spectroscopy, showed anomalous spectra of nucleic acids rather than the expected nucleoproteins. These alterations resulted in no seed transmission beyond the first plant generation. Altogether, the results show for the first time that correct virion assembly is needed for seed infection from the mother plant but not to seedling invasion from the seed. We propose that incorrect virion formation, self-assembly and architecture stability might be explained if during the first stages of germination and seedling development some tobacco seed factors target viral regions responsible for protein-RNA interactions
Design, synthesis and biological evaluation of indane 2-arylhydrazinylmethylene-1,3-diones and indol-2-aryldiazenylmethylene-3-ones as b-amyloid aggregation inhibitors
No full textBiological screening of (hetero)aromatic compounds allowed the identification of some novel inhibitors
of Ab1–40 aggregation, bearing indane and indole rings as common scaffolds. Molecular decoration of lead
compounds led to inhibitors exhibiting a potency, measured by the Thioflavin T fluorimetric assay,
ranging from high to low micromolar IC50. The 2-(p-isopropylphenyldiazenylmethylene)indolone
derivative 6c resulted as the most potent aggregation inhibitor exhibiting an IC50 of 1.4 mM, with
complete lack of fibril formation as confirmed by transmission electron microscopy. Structure–activity
relationships suggested that binding to the Ab peptide may be largely guided by p-stacking and
hydrogen bond interactions
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