1,721,068 research outputs found
Molecular studies on a large multi-gene family of polygalacturonases in two different phytophthora species
Full text linkThe plant cell wall is a structural barrier to pathogens, composed of a network of polysaccharides such as cellulose, hemicellulose and pectin. The majority of pathogenic microorganisms produce cell wall degrading enzymes (CWDEs) that are essential for the invasion process. Among the different CWDEs, polygalacturonases (PGs) play a critical role since their action on pectin makes other cell wall components more accessible to other CWDEs and causes tissue maceration. PGIPs (polygalacturonase-inhibiting proteins) are plant cell wall proteins that specifically modulate the activity of the PGs, and hamper the invasion process by limiting the host tissue colonization. The PG–PGIP interaction retards pectin hydrolysis and favors oligogalacturonide (OGs) accumulation and leading to plant defense activation. This work wants to contribute to study the role of the PGs in P. nicotianae and P. capsici, among the most dangerous pathogens for many plant species: Specific points of this thesis are: 1) Identification of the whole set of the PGs from well-known oomycetes, which present different lifestyles. 2) Comparison of large PG families found in the oomycetes species using phylogenetic analysis for tracking evolutionary relationships. 3) Analysis of amino acid sequences on identified PGs to detect domains and/or amino acids involved in PG-PGIP interaction. 4) Characterization of PGs from P. nicotianae and P. capsici. 5) Construction of P. capsici mutants for investigate the role of PGs in the pathogenesis, using different approach of reverse genetics.
The results from this thesis enhances the hypothesis that the multiplicity of PGs may give flexibility to the pathogen, with each enzyme having its own unique properties to contribute to the performance of all the enzymes to successfully colonize plants.Nei primi stadi dell’infezione, i microrganismi fitopatogeni producono un arsenale di enzimi che depolimerizzano in maniera ordinata e sequenziale i componenti della parete cellulare vegetale (CWDEs - Cell Wall Degrading Enzymes). Le poligalatturonasi (PG) sono tra i primi enzimi pectici ad essere prodotti e favoriscono la macerazione del tessuto vegetale rendendo accessibili a cellulasi ed emicellulasi gli altri componenti della parete. I carboidrati rilasciati dal processo degradativo della parete cellulare vengono utilizzati dal patogeno per il sostentamento e per la crescita, conferendo al processo di degradazione un ulteriore significato biologico oltre quello di distruzione fisica della parete. Le PGIP (PolyGalacturonase Inhibiting Proteins) presenti nella parete cellulare vegetale, sono delle glicoproteine in grado di inibire e/o modulare in maniera specifica l’attività delle PG. La formazione del complesso PG-PGIP rallenta la capacità delle PG di degradare l’omogalatturonano della parete cellulare, favorendo l’accumulo di oligogalatturonidi in grado di attivare le risposte di difesa della pianta.
Questo lavoro vuole contribuire allo studio del ruolo delle PG in Phytophthora nicotianae e Phytophthora capsici, che sono ritenuti tra gli agenti patogeni più pericolosi per molte specie vegetali. Argomenti specifici che vengono affrontati in questa tesi riguardano: 1) l’identificazione di PG da alcune specie di oomiceti considerate tra le più pericolose per le piante (generi Phytophthora, Pythium ed Aphanomycetes); 2) l'analisi filogenetica delle famiglie geniche PG; 3) l’analisi di sequenze proteiche delle PG identificate allo scopo di rilevare domini e/o amminoacidi responsabili dell'interazione PG-PGIP; 4) la caratterizzazione delle PG da P. nicotianae e P. capsici; 5) la costruzione di mutanti di P. capsici per indagare il ruolo di PG nella patogenesi, utilizzando diversi approcci di genetica “reverse”
I risultati ottenuti in questa tesi, potenziano l'ipotesi che la molteplicità delle PG può dare flessibilità al patogeno e ogni PG, con le proprie caratteristiche uniche, contribuisce alla performance del patogeno per colonizzare le piante con successo.Dottorato di ricerca in Scienze e tecnologie biologiche ed ambientali (XXVII ciclo
A divergent polygalacturonase of Fusarium phyllophilum shows sequence and functional similarity to the enzyme of F. verticillioides
No full textEndopolygalacturonases (endoPGs) are fungal enzymes
secreted during the infection in order to degrade
plant cell wall pectins. In Fusarium spp., endoPGs are
among the first enzymes produced during infection and
play a crucial role in plant tissue penetration and colonization.
The endoPG of F. phyllophilum strain FC-10,
previously classified as F. verticillioides, is the best characterized
Fusarium cell wall degrading enzyme. In this
work we have carried out a phylogenetic analysis of the
endoPG (pg) gene sequence that confirms the classification
of the FC-10 strain as F. phyllophilum, and also
shows an unexpected divergence of the pg gene of F.
phyllophilum strain NRRL 25305. This gene and the
biochemical characteristics of the encoded product appear
more closely related to those of F. verticillioides pg.
This observation and the evidence that endoPGs have
experienced positive selection indicate that selective
pressure acting on these enzymes may limit the use of
their gene sequences as reliable markers for phylogenetic
studie
The polygalacturonase-inhibiting protein PGIP2 of Phaseolus vulgaris has evolved a mixed mode of inhibition of endopolygalacturonase PG1 of Botrytis cinerea
Full text linkBotrytis cinerea is a phytopathogenic fungus that causes gray mold in > 1,000 plant species. During infection, it secretes several endopolygalacturonases (PGs) to degrade cell wall pectin, and among them, BcPG1 is constitutively expressed and is an important virulence factor. To counteract the action of PGs, plants express polygalacturonase-inhibiting proteins (PGIPs) that have been shown to inhibit a variety of PGs with different inhibition kinetics, both competitive and noncompetitive. The PG-PGIP interaction promotes the accumulation of oligogalacturonides, fragments of the plant cell wall that are general elicitors of plant defense responses. Here, we characterize the enzymatic activity of BcPG1 and investigate its interaction with PGIP isoform 2 from Phaseolus vulgaris (PvPGIP2) by means of inhibition assays, homology modeling, and molecular docking simulations. Our results indicate a mixed mode of inhibition. This is compatible with a model for the interaction where PvPGIP2 binds the N-terminal portion of BcPG1, partially covering its active site and decreasing the enzyme affinity for the substrate. The structural framework provided by the docking model is confirmed by site-directed mutagenesis of the residues that distinguish PvPGIP2 from the isoform PvPGIP1. The finding that PvPGIP2 inhibits BcPG1 with a mixed-type kinetics further indicates the versatility of PGIPs to evolve different recognition specificities
GC-MS analysis of the essential oils of Juniperus communis L. berries growing wild in the Molise region: Seasonal variability and in vitro antifungal activity
No full textCloning and characterization of the gene encoding the endopolygalacturonase of Fusarium moniliforme
No full textThe interaction of Botrytis cinerea polygalcturonase (PG1) with PGIPs from different plants
No full textCrystallization and preliminary X-ray diffraction study of the endopolygalacturonase from Fusarium moniliforme
No full textAnalysis of the interaction between PGIP from Phaseolus vulgaris L. and fungal endopolygalacturonases using biosensor technology
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