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Corrigendum: Characterization and expression of Fusarium graminearum endo-polygalacturonases in vitro and during wheat infection
No full textFusarium graminearum cerato-platanin proteins weaken cellulosic materials and enhance cellulase activity in an expansin-like manner
No full textCerato-platanin proteins (CPPs) belong to a family of small secreted non-catalytic fungal proteins with phytotoxic activity. CPPs have been recently classified as expansin-like proteins because of structural and functional features related to plant expansins, small secreted proteins able to loosen and disrupt the non-covalent bonding networks of plant cell wall polysaccharides without enzymatic activity. The genome of Fusarium graminearum, the causal agent of Fusarium head blight disease of wheat and other cereal grains, contains two genes putatively encoding for CPPs (FgCPPs). To characterize their role, the two proteins have been heterologously expressed in yeast. Enzymatic assays have shown the ability of the recombinant FgCPPs to reduce the viscosity of a cellulose soluble derivate (carboxymethyl cellulose, CMC) mainly with a non-enzymatic activity. Indeed, differently from other fungal CPPs and similarly to expansins, FgCPPs seem trapped by cellulose and not by chitin, thus suggesting that they could interact with cellulose. The incubation of CMC with a cellulase in presence or absence of the two recombinant proteins has shown that the FgCPPs enhance cellulase activity. A double knock-out mutant deleted of both FgCPPs encoding genes produces higher cellulase activity when grown on CMC, thus suggesting that the absence of FgCPPs forces the fungus to produce more cellulase activity to compensate for the lack of expansin-like activity. Finally, the preliminary demonstration that the FgCPPs act also loosening filter paper, a natural insoluble cellulose, could suggest a possible future biotechnological application in second-generation biofuels production from agricultural lignocellulosic biomasses rich in cellulose
A single amino acid substitution in highly similar endo-PGs from Fusarium verticillioides and related Fusarium species affects PGIP inhibition
No full textEndo-polygalacturonase (PG) may be a critical virulence factor secreted by several fungi upon plant invasion. The single-copy gene encoding PG in Fusarium verticillioides and in eight other species of the Gibberella fujikuroi complex (F. sacchari, F. fujikuroi, F. proliferatum, F. subglutinans, F. thapsinum, F. nygamai, F. circinatum, and F. anthophilum) was functionally analyzed in this paper. Both the nucleotide and amino acid sequences were highly similar among the 12 strains of F. verticillioides analyzed, as well as among those from the G. fujikuroi complex. The PGs were not inhibited by the polygalacturonase-inhibiting proteins (PGIPs) from the monocot asparagus and leek plants, but were inhibited to variable extents by bean PGIP. PGs from F. verticillioides, F. nygamai and one strain of F. proliferatum were barely inhibited. Residue 97 within PG was demonstrated to contribute to the different levels of inhibition. Together these findings provide new insights into the structural and functional relationships between the PG from the species of the G. fujikuroi complex and the plant PGIP. © 2007 Elsevier Inc. All rights reserved
The Fusarium graminearum cerato-platanins loosen cellulose substrates enhancing fungal cellulase activity as expansin-like proteins
No full textCerato-platanin proteins (CPPs) are small non-catalytic, cysteine-rich hydrophobic proteins produced by filamentous fungi. The genome of Fusarium graminearum, the causal agent of Fusarium head blight disease of wheat and other cereal grains, contains two genes putatively encoding for CPPs. To better characterize their features, the two FgCPPs were heterologously expressed in Pichia pastoris. The recombinant FgCPPs reduced the viscosity of a cellulose soluble derivate (carboxymethyl cellulose, CMC). The same effect was not observed on other polysaccharide substrates such as chitin, 1,3-β-glucan, xylan and pectin. Indeed, differently from other fungal CPPs and similarly to expansins, FgCPPs are trapped by cellulose and not by chitin, thus suggesting that these proteins interact with cellulose. A double knock-out mutant deleted of both FgCPPs encoding genes produce smuch more cellulase activity than the corresponding wild type strain when grown on CMC, likely compensating the absence of FgCPPs. This result prompted us to investigate a possible synergistic effect of these proteins with fungal cellulases. The incubation of FgCPPs in the presence of a fungal cellulase (EC 3.2.1.4) determines an increased enzymatic activity on CMC, filter paper and wheat cell walls. The observation that FgCPPs act with a non-hydrolytic mechanism indicates that these proteins favor fungal cellulase activity in an expansin-likemanner. Though the disruption of the FgCPP genes had no demonstrable impact on fungal virulence, our experimental data suggest their probable involvement in virulence, thus we refer to them as accessory virulence genes. Our results suggest also that the FgCPPs could be exploited for future biotechnological application in second-generation biofuels production on lignocellulosic biomasses rich in cellulose. Finally, we demonstrate that FgCPPs act as elicitors of defense responses on Arabidopsis leaves, increasing resistance to Botrytis cinerea infections
Overexpression of pectin methylesterase inhibitors in Arabidopsis affects defence against pathogens
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Peptide-Based Biopesticides
No full textIn this presentation we describe the great potential of peptides as biopesticides. Currently Europe is greatly encouraging research in sustainable pest-management. Finding eco-friendly, effective alternatives to synthetic pesticides is of paramount importance, especially against the so-called priority pests of fruits and vegetables. For some of these pests, such as botrytis cinerea and peronospora viticola, no effective bio-alternatives to small organic molecules are available so far. Fungi belonging to the genus Trichoderma are distributed worldwide and have been used successfully in field trials against many crop pathogens. They produce peptaibols, a peculiar family of peptides, as part of their defense system against other microorganisms. Such secondary metabolites are known for their plantprotection properties: they (i) possess antimicrobial activity, (ii) act as stimulants of plant defences and growth (iii) elicit plant production of volatiles to attract natural enemies of herbivorous insects. By means of a versatile SPPS strategy, we produced several analogs of such naturally occurring peptides. With such compounds, we can circumvent both the health hazards and the unreliable effectiveness in open field connected with the use of antagonistic microorganisms as biological control agents, while keeping the biomolecules responsible for their beneficial effects. Our peptides have been tested (alone or in combination) both in vitro and in vivo against a variety of priority pests, such as the fungi Botrytis cinerea and Penicillum italicum, and the bacterium Pectobacterium carotovorum. We identified several peptaibol analogs with a broad-spectrum activity as biopesticides, able to completely inhibit the growth of B. cinerea and many other pathogens for over a week at low micromolar concentrations
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