1,721,045 research outputs found
Inhibition of tobacco necrosis virus (TNV) and potatovirus X (PVX) replication in plants by human interferon
No full textHuman interferon treatments, carried out right after virus inoculation caused in both cases (TNV in Chenopodium amaranticolor, PVX in Gomphrena globosa) a remarkable reduction of virus synthesis in plants. The possibly produced antiviral-active oligoadenylates were recovered
Salicylic acid enhances the synthesis of TobaccoNecrosis Virus (TNV) and inhibits formation of antiviral factors in Chenopodium amaranticolorplants
No full textSalicylic acid (SA) is often regarded as a signal molecule involved in systemic acquired resistance (SAR) against plant virus infections. When infiltrated into Chenopodium amaranticolor leaves 12 h prior to inoculation with tobacco necrosis virus (TNV), it caused an increase in virus synthesis. It seems therefore, that in our system, SA is involved in a mechanism of acquired susceptibility rather than acquired resistance to TNV. These results are different from all others previously reported for virus infection and question the proposed SA general role of signal molecule triggering plant defence mechanism against pathogens. Our is not the first evidence of SA-suppressed resistance in plants. This together with previous researches where SA neither induced PR-protein formation nor induced acquired resistance to virus infections, support the idea that plant SAR is a complex phenomenon, probably depending on various mechanisms. One of them is the impaired formation of antiviral factors in the interaction system C. amaranticolor/TNV
Plant stress and mycotoxin accumulation in maize
No full textThe 2012 crop year in north-east Italy was characterized by a strong heat-wave event, and areas influenced by this environmental condition presented an anomalous accumulation of mycotoxins in maize. Mycotoxins are secondary metabolites, harmful to human and animals, produced by pathogenic fungi that contaminate foodstuffs. Plants suffering by stress are characterized by lower crop yield and quality, increased fungal infection and in some cases by higher amounts of mycotoxins. In plant, heat-wave events and generally stress factors afflict physiological traits and are associated with oxidative stress. Since oxidative stress is fundamental also for activation of mycotoxin biosynthesis in fungi, stress conditions in plant and mycotoxin accumulation are often correlated. The present paper aims to report the influence of some stress factors in relation to mycotoxin accumulation providing further data to comprehension of stress management with particular emphasis to heat-wave related events
Pectin methylesterases affect plant resistance to pathogens
No full textPectin is synthesized in a highly methyl esterified form and is de-esterified in muro by pectin methyl esterases (PMEs). The degree and pattern of methyl esterification affect the cell wall structure and properties with consequences on their resistance to pathogens. We show that PME is required for the initial plant tissue colonization by fungal and bacterial necrotrophs, making pectin more susceptible to the action of the hydrolytic enzymes of the pathogens. We have reduced the susceptibility of plants to pathogens by increasing the methyl esterification of pectin through the overexpression of PME inhibitors (PMEI). A natural Arabidopsis ecotype, showing a higher pectin esterification and lower homogalacturonan content than the reference ecotype Col-0 is more resistant to necrotrophic fungal and bacterial pathogens. PME is also required for viral cell-to-cell and long-distance movement of plant virus. Our results support the notion that PME activity affects the mechanical properties of cell wall and plant resistance against pathogens
Endo-PGs from species of the Gibberella fujikuroi complex provide new insight into the PG-PGIP interaction
No full textSeveral Fusarium species of the Gibberella fujikuroi complex are toxigenic and able to induce diseases on many crops, especially cereals. At early stages of the infection process, these fungi produce endo-polygalacturonase (PG) activity which degrades the host cell wall pectic polymers. Plants, on the other hand, contain polygalacturonase-inhibiting proteins (PGIPs) in their tissues which may contrast the fungal infection by inhibiting the PG activity. We observed that the PGs from several species of the Gibberella fujikuroi complex (F. verticillioides, F. sacchari, F. fujikuroi, F. proliferatum, F. subglutinans, F. thapsinum, F. anthophilum, F. nygamai, F. circinatum) are not inhibited by PGIPs extracted from asparagus and leek monocot plants. Instead, these PGs were inhibited to variable extents by the PGIP extracted from bean. The PGs ranked into four groups of inhibition when assayed against the bean PGIP. Specifically, the PGs from F. verticillioides and F. nygamai were the least inhibited and those from F. thapsinum were low inhibited; the PGs from F. sacchari, F. fujikuroi and F. proliferatum were inhibited at an intermediate level, while the PGs from F. anthophilum, F. circinatum and F. subglutinans were the most inhibited. The genes encoding these fungal PGs were cloned, and the multiple alignments of the deduced amino acid sequences allowed identifying the few amino acid substitutions likely involved in the different binding with the bean PGIP. Site-directed mutagenesis experiments showed that the amino acid in position 122 is crucial for recognition of the Fusarium PGs by the bean PGIP
Transgenic Expression of Pectin Methylesterase Inhibitors in Arabidopsis and Tobacco limits Tobamovirus spreading
No full textViral infection is a complex process influenced by the balance of virus-encoded proteins and host factors which support virus replication, cell-to-cell and long distance movement through the plant. Virus-encoded movement proteins (MPs) are necessary to allow cell-to-cell spread through plasmodesmata (PD). The interaction of MP with plant pectin methylesterase (PME) is required for Tobacco mosaic virus (TMV) local spreading in tobacco.
The viral exit out of the vascular system is also partly PME-dependent. Pectin demethylation directed by PME is likely to be a source of methanol that has been recently found to facilitate TMV spreading by triggering PD dilation. We here report that the expression of a PME inhibitor from Actinidia chinensis (AcPMEI) in Nicotiana tabacum decreases the overall PME activity and increases the level of pectin methylesterification of the wall without affecting plant morphology and development. After inoculation with TMV the transformed plants expressing AcPMEI exhibited a significant delay of viral spreading. A reduced susceptibility against Turnip vein clearing virus (TVCV) infection was also observed in Arabidopsis plants overexpressing the AtPMEI-2 inhibitor. Overall, our results indicate PMEIs as efficient tools to limit Tobamovirus infection
CONSTITUTIVE EXPRESSION OF PECTIN METHYLESTERASE INHIBITORS LIMITS TOBAMOVIRUS SPREADING IN TOBACCO AND ARABIDOPSIS
No full textPlant viral infection is a complex process influenced by the interaction of virus-encoded proteins and host factors which support virus replication and movement. Successful infection requires viral movement proteins (MPs) that modify the plasmodesmata (PD) size exclusion limit during the cell-to-cell movement. Pectin methylesterase (PME) was shown to interact in vitro with the MP of different viruses and the MP-PME interaction was proposed to be necessary for Tobacco mosaic virus (TMV) cell-to-cell spreading. PME is also required for the systemic movement of TMV through the host vasculature. Pectin demethylation directed by PME is likely to be a source of methanol that has been recently found to facilitate TMV spreading by triggering PD dilation. We here report that the ectopic expression of a PME inhibitor from Actinidia chinensis (AcPMEI) in Nicotiana tabacum significantly delays the TMV cell-to-cell and systemic spreading. A reduced susceptibility against Turnip vein clearing virus (TVCV) was also observed in Arabidopsis plants overexpressing a PME inhibitor from Arabidopsis (AtPMEI-2). Overall, our results indicate PMEIs as efficient tools to limit Tobamovirus infection
Characterization of endopolygalacturonase of species belonging to the Gibberella fujikuroi complex
No full textThe Gibberella fujikuroi complex includes toxigenic and pathogenic fungal species able to produce disease on several economically important crops. In order to understand the involvement of the endopolygalacturonase (endo-PG) in the infection process we have first purified the endo-PG produced in culture by eight species (from two to four isolates of Fusarium verticillioides, F. sacchari, F. fujikuroi, F. proliferatum, F. subglutinans, F. thapsinum, F. nygamai, F. circinatum) belonging to the complex, and then cloned the corresponding genes. The coding sequence of the endo-pg gene permitted to distinguish clearly the different species according to the classification obtained with the partial sequence of the translation elongation factor (TEF), a molecular marker widely used to distinguish identify Fusarium species. The deduced aminoacidic sequence of endo-PGs were very similar among the species and quite identical within the species. The endo-PGs displayed similar properties when assayed against different substrates but showed diverse behaviors in the presence of plant inhibitors (PGIP). In particular, all endo-PGs were not inhibited by PGIP from monocot plants (like aparagus and maize) but presented various degree of inhibition when assayed against the bean PGIP, with the endo-PG from F. verticillioides being the less inhibited. Considering that many species of the G. fujikuroi complex are pathogens of monocot plants, their endo-PG appears particularly adapted to overcome the hindrance of the host PGIPs
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