1,721,149 research outputs found
Gel detection of Allium porrum polygalacturonase-inhibiting protein reveals a high number of isoforms
No full textPolygalacturonase inhibiting proteins PGI Ps are leucine-rich repeat glycoproteins. localized in the cell wall of most plant species, capable of countering the activity of endo-polygalacturonases (endo-PGs) produced by phytopathogenic fungi. The PGIP from Allium porrum leaves was analysed to ascertain the presence of different molecular forms of PGIP. Leek PGIP was separated into two fractions: a soluble and an ionically wall-bound PGIP, each of which was then purified by cation-exchange chromatography. Two and three peaks of PGIP activity were obtained, respectively. PGIP isoforms contained in each peak were separated by isoelectrofocusing (IEF) on a polyacrylamide gel. Following the separation, the gel was first overlaid with sodium polygalacturonate and then treated with the endo-PG from either Sclerotinia sclerotiorum, Fusarium moniliforme or Botrytis aclada. The endo-PG(s) hydrolyse the overlaid substrate except where active inhibitors are present. The presence of PGIPs is revealed by ruthenium red staining of the nonhydrolysed substrate. Each PGIP peak following IEF separation revealed several PGIP isoforms with pIs between 5.0 and 7.0. More than 20 isoforms were detected in total. with considerable differences in their inhibitory activity. While similar PGIP isoform patterns were obtained by developing the IEF gels with the endo-PGs of S. sclerotiorum and B. aclada, less intense PGIP bands were observed with the endo-PG from B. aclada, consistent with inhibition assays performed in solution. The endo-PG from F. moniliforme, which is not inhibited at all by leek PGIP in solution, consistently showed no PGIP band on the gel assay
Effects of chlormequat on growth, dry matter partitioning, net assimilation and yield of zucchini (Cucurbita pepo L.) grown under tunnel for delayed production
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Polygalacturonase regulation in Sclerotinia sclerotiorum: effect of carbon source on the isoenzymatic pattern
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CHARACTERIZATION OF 2 SCLEROTINIA-SCLEROTIORUM POLYGALACTURONASES WITH DIFFERENT ABILITIES TO ELICIT GLYCEOLLIN IN SOYBEAN
No full textTwo endo-polygalacturonase isoenzymes (PG-II and PG-IV), with masses of 34 and 30 kDa respectively, were purified from soybean hypocotyls infected by Sclerotinia sclerotiorum. The pH optimum for both isoenzymes was about 4.6, but PG-IV exhibited a broader range of pH activity. PG-IV showed a much higher affinity for pectin than did PG-II. PG-II hydrolyzed polygalacturonic acid in a more random fashion than PG-IV. Oligouronides produced by PG-II showed a higher phytoalexin elicitor activity. PG-IV produced a large degree of maceration of soybean hypocotyls releasing a significant amount of uronides. The properties of PG-II and PG-IV are discussed in relation to the different ability of the two isoenzymes to elicit glyceollin in soybean
INHIBITION OF SOME ROT FUNGI POLYGALACTURONASES BY ALLIUM-CEPA L AND ALLIUM-PORRUM L EXTRACTS
No full textExtracts of Allium cepa and A. porrum contain factors that inhibit to various extents polygalacturonases (PGs) produced in vitro by Sclerotinia sclerotiorum, Botrytis cinerea, Fusarium moniliforme, Phoma terrestris, Sclerotium cepivorum, Macrophomina phaseolina, Didymella bryoniae and Phoma lycopersici. The PG inhibition rank changed using leek or onion extract. The inhibition factors are possibly proteins, do not present particular specificity and act against PGs of fungi pathogens and non pathogens for these plant species
Relationships 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
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
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