1,721,143 research outputs found
Fungal pathogens can elude the inhibition by host plant polygalacturonase inhibiting proteins (PGIPs) by different mechanisms
No full textRelationships among endo-polygalacturonase, oxalate, pH, and plant polygalacturonase-inhibiting protein (PGIP) in the interaction between Sclerotinia sclerotiorum and soybean
No full textThe necrotrophic fungal pathogen Sclerotinia sclerotiorum secretes oxalic acid and endo-polygalacturonase (endo-PG) in host plants. Oxalic acid acidifies the plant tissue to values more suitable to endo-PG activity. However, we observed that the soybean infected seedlings possessed a pH of 3.8 which is below that optimal for endo-PG activity (4.5-5.0). We investigated, therefore, the effects of pH (from 5.0 to 3.6) and oxalate (5-20 mM) on the activity of the major basic endo-PG (PGb) and towards an acidic endo-PG (PGa), secreted by S. sclerotiorum during soybean infection. We verified that only PGb activity is stimulated by oxalate while, at the lowest pHs, PGa escapes the inhibition of a soybean polygalacturonase-inhibiting protein (PGIP). These results, performed on polygalacturonic acid, were apparently consistent with data obtained from soybean hypocotyl segments, where PGb activity was increased by oxalate and PGa maintained its activity also at pH 3.6, possibly because at this pH the PGIP contained in the plant tissue is inactive. RT-PCR analysis showed that, during soybean infection, the expression of the putative pga gene is delayed in comparison to the basic one. The different temporal expression of the two endo-PGs and their different response to pH, oxalate and PGIP seem to be consistent with a possible maximisation of the fungal PG activity in the host tissue
PEPTIDES SIMILAR TO THE NATURAL PEPTAIBOL TRICHOGIN GA IV WITH PHYTOSANITARY ACTIVITIES
No full textThe invention relates to new peptides and their use as pesticides. In particular, these peptides have been advantageously used for the treatment of vine peronospora (downy mildew)
Cerato platanins (CP) of Fusarium graminearum induce defense responses in plant and are not essential for fungal virulence.
No full textCerato platanins (CP) belong to a family of small secreted fungal proteins with phytotoxic activity which seem to induce defense responses and necrosis in plants and contribute to Botrytis cinerea and Magnaporthe grisea virulence.
In the genome of F. graminearum, a necrotrophic fungal pathogen which causes Fusarium head blight (FHB) disease of wheat, barley and other cereal grains, there are two genes (FGSG_10212 and FGSG_11205) putatively encoding for CP-like proteins that we cloned and heterologously expressed in Pichia pastoris. The recombinant proteins, native and boiled, resulted able to reduce the viscosity of carboxymethyl cellulose, in particular the FgCP11205. Treatments of Arabidopsis thaliana leaves with the two F. graminearum CPs induced necrotic symptoms, accumulation of H2O2 and expression of defense genes, specifically PR1, marker of salicylic acid signaling, and ERF1b, a transcriptional regulator of some ethylene-responsive genes.
Being these CPs able to induce defense responses, we tested their effectiveness in increasing the resistance of A. thaliana to the fungal pathogen B. cinerea; treatments with both CPs determined a reduction of lesion size of about 30-40%.
The expression of the two cp genes was analyzed by qPCR in the early stages of wheat spike infection and during in vitro growth and only the Fgcp10212 gene resulted strongly transcribed. To verify the contribution of F. graminearum CPs to fungal virulence, single and double gene knock-out mutants were produced and used to infect host plants such as wheat and soybean but their virulence resulted comparable to that of the wild-type strain
Polygalacturonase from an isolate of Fusarium moniliforme escapes inhibition by plant PGIPs
No full textThe xylanase inhibitor TAXI-III limits cell death induced by a xylanase secreted by Fusarium graminearum during wheat infection.
No full textCereals contain xylanase inhibitor proteins (XIs) which inhibit microbial xylanases from glycoside hydrolase families 10 and 11. In wheat, three types of XIs have been identified: Triticum aestivum XI (TAXI), xylanase inhibitor protein (XIP) and thaumatin-like XI (TLXI). These inhibitors are considered part of the defence mechanisms that plants use to counteract microbial pathogens and recently we provided in planta evidences for the protective role of TAXI-III, a member of the TAXI type XIs. To elucidate the molecular mechanism underlying the capacity of the transgenic plants expressing Taxi-III to limit Fusarium Head Blight (FHB) disease symptoms caused by F. graminearum, we performed infiltration experiments on wheat tissues with a xylanase strongly expressed by F. graminearum during wheat spike infection which we have previously demonstrated to induce cell death and hydrogen peroxide accumulation. Experiments performed on glumes of flowering wheat spikes showed that the presence of TAXI-III significantly decreased cell death and hydrogen peroxide accumulation. Most interestingly, similar results were also obtained by infiltrating the same xylanase on glumes of transgenic wheat plants expressing TAXI-III. These results suggest that the reduced FHB symptoms on transgenic TAXI-III plants can be due to the direct inhibition of xylanase activity secreted by the pathogen but also to the capacity of TAXI-III to prevent the recognition of xylanase by a plant receptor possibly involved in cell death elicitation
Grape berry proteins act as scavengers of grape polyphenols and protect polygalactutonase activity of Botrytis cinerea from inhibition
No full textAt maturity grape berries contain a large amount of proteins and polyphenols with potential anti-fungal activity. The protein fraction of grape extract includes mostly thaumatin-like proteins and chitinase while flavonoids predominate among polyphenols.
However, Botrytis cinerea grows well in the presence of proteins and polyphenols when these molecules are supplied to the culture in a ratio similar to that measured in the grape fruit extract.
In vitro it was observed that a fraction of grape proteins interacts with polyphenols forming complexes with reduced solubility and that B. cinerea laccase enhances this process. Polyphenols are well known inhibitors of fungal polygalacturonases (PGs) activity, and B. cinerea PG activity is inhibited by grape polyphenols in vitro.
However, the simultaneous administration of grape proteins diminishes the inhibitory activity of grape polyphenols, and laccase addition restores completely B. cinerea PG activity. Similar results
are obtained when the stylbenic phytoalexin resveratrol is used in combination with grape proteins and B. cinerea laccase. The scavenging of polyphenols by grape proteins could favour the berry
infection by B. cinerea
Fungal strategies to elude polygalacturonase inhibition by plant PGIPs
No full textPolygalacturonase inhibiting proteins (PGIPs) are plant defence molecules able to block the polygalacturonase activity of fungal pathogens. However, fungi have evolved strategies to overcome PGIP inhibition. For example, Sclerotinia sclerotiorum in the early stage of soybean infection produces considerable amount of PG activity encoded by a basic pg gene. By quantitative RT-PCR it was shown that initially the transcript of this pg gene overcomes by one hundred fold the transcript of the soybean pgip gene. Thereafter, pgip gene was noticeably induced and a second pg gene was expressed. This gene encodes a PG that, in the acidic pH conditions determined in diseased tissue by fungal secretion of oxalic acid, is less sensitive to PGIP. In other cases, PGIP may fail to recognise specific PGs produced by some fungi. For example, a PG refractory to all PGIPs was isolated from a Fusarium moniliforme strain. The comparison of the amino acidic sequence of this PG with that obtained from a different F. moniliforme isolate susceptible to PGIP inhibition allowed the identification of a few amino acidic substitutions responsible for escaping inhibition. Further studies using overlap extension of the two PG sequences and site-directed mutagenesis will permit to identify specific amino acids responsible for the lack of recognition by plant PGIP
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