1,721,029 research outputs found
Generalità sui fitoplasmi.
No full textI fitoplasmi sono batteri fitopatogeni non coltivabili in vitro appartenenti alla classe Mollicutes. Privi di parete e di dimensioni submicroscopiche appaiono pleomorfici all’osservazione al microscopio elettronico a trasmissione; solo lo studio di porzioni di acido nucleico (particolarmente il DNA codificante i geni ribosomici) ha permesso di giungere alla classificazione molecolare che è oggi alla base delle indagini patologiche ed epidemiologiche volte alla comprensione dei meccanismi biologici che regolano l’insediarsi ed il diffondersi delle malattie associate questi patogeni. Poichè i fitoplasmi vengono classificati esclusivamente in base alla sequenza di geni ribosomici non possono essere formalmente denominati col consueto binomio latino di genere e specie, ma ricadono in una categoria provvisoria per la quale è stato di recente adottato il termine Candidatus, da associarsi al binomio latino. Parallelamente alla risoluzione del problema tassonomico, il progresso e l’accessibilità di metodologie di analisi molecolare hanno consentito lo sviluppo di protocolli diagnostici che in alcuni casi sono oggi applicati su vasta scala
Oltre la forma: sistematica molecolare e diagnostica fitopatologica
No full textLavoro ad invito presentato al IV Convegno dell'Associazione Italiana delle Società Scientifiche Agrarie (AISSA), Mosciano S.Angelo (TE), 5-6 Dicembre 2006, in rappresentanza della Società Italiana di Patologia Vegetal
USE OF POLYMERASE CHAIN-REACTION TO PRODUCE OLIGONUCLEOTIDE PROBES FOR MYCOPLASMALIKE ORGANISMS
No full textPolymorphisms at the 3’end of the movement protein (MP) gene of grapevine Pinot gris virus (GPGV) affect virus titre and small interfering RNA accumulation in GLMD disease
No full textGrapevine Leaf Mottling and Deformation (GLMD) is a grapevine disease that has been associated with a trichovirus, the grapevine Pinot gris virus (GPGV). A wide diversity in the severity of GLMD disease symptoms has been recorded worldwide, but the relationship of this diversity to the sequence variation in the GPGV genome is still a matter of debate. Results from comparative analysis of GPGV genomic sequences have suggested an association of polymorphisms at the 3’-end of the movement protein (MP) with GLMD severity. Here, the 3’-terminus of the MP gene of a GPGV infectious clone derived from an isolate from grapevine showing severe symptoms (fvg-12), was substituted with a 356 bp synthetic DNA fragment having a sequence resembling that of another GPGV isolate (fvg-15), recovered from an asymptomatic grapevine. The clone containing this chimeric construct was root-inoculated in virus-free Kober rootstocks along with the clones containing the fvg-12 and fvg-15 full length sequence. Remarkable differences in virus titre, accumulation of GPGV-derived small interfering RNAs (siRNAs), alterations in the gene expression of boron transporters and, to a lesser extent, in symptom expression were recorded among plants infected with either one of the three GPGV derived clones. In particular, the chimeric clone behaviour was indistinguishable from that of the donor of the small 356 bp fragment and significantly different from the other. Thus, this work experimentally confirmed the critical role of the GPGV-MP C-terminus in determining the fate of the infection, as it had been previously hypothesized on the basis of comparative sequence analysis
Assembly of Phytoplasma Genome Drafts from Illumina Reads Using Phytoassembly
No full textGenome drafts for the phytoplasmas may be rapidly and efficiently assembled from NGS sequence data alone exploiting the proper bioinformatic tools and starting from properly collected samples. Here, we describe the use of the Phytoassembly pipeline (https://github.com/cpolano/phytoassembly ), a fully automated tool that accepts as input row Illumina data from two samples (a phytoplasma infected sample and a healthy reference sample) to produce a phytoplasma genome draft, using the healthy plant host genome as a filter and profiting from the difference in reads coverage between the genome of the pathogen and that of the host. For phytoplasma infected samples containing >2% of pathogen DNA and an isogenic healthy reference sequence the resulting assemblies span the almost entire genomes
‘Candidatus Erwinia dacicola’ sp. nov., a coevolved symbiotic bacterium of the olive fly Bactrocera oleae (Gmelin)
No full textThe taxonomic identity of the hereditary prokaryotic symbiont of the olive fly Bactrocera oleae (Diptera: Tephritidae) was investigated. In order to avoid superficial microbial contaminants and loosely associated saprophytic; biota, flies were surface-sterilized at the larval stage and reared under aseptic conditions until adult emergence. B. oleae flies originating from different geographical locations and collected at different times of the year were tested. Bacterial isolation was undertaken from the cephalic oesophageal bulb, which is known to be a specific site of accumulation for the hosted microsymbionts in the adult insect. Despite evidence of multiplication cycles taking place within the insect, attempts at cultivation of the isolated bacteria ex situ were not productive at any stage, leading to the choice of unculturable, status definition. PCR amplification and nucleotide sequencing of the entire 16S rRNA gene consistently yielded a single sequence that displayed marked similarity with enterobacterial lineages, with closest matches (97%) to Erwinia persicina and Erwinia rhapontici. The novel taxon differs from common intestinal bacterial species of fruit flies and from instances of culturable bacteria previously described in B. oleae raised without sterility precautions, which we also observed as minority occupants or occasional contaminants. The symbiont's identity is also distinct from Pseudomonas savastanoi. In all observations, the numerically dominant inhabitant of the olive fly oesophageal organ was the same unculturable organism, whose presence at later stages was also regularly observed in the midgut. A novel species is proposed, by virtue of its unique properties, under the designation 'Candidatus Erwinia dacicola'
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