169,934 research outputs found
Generation type inequalities for closed linear operators related to domains with conical points
No full textLet be a second-order linear differential operator in divergence form. We prove that the operator , where λ ∈ C and I stands for the identity operator, is closed and injective when Re λ is large enough and the domain of consists of a special class of weighted Sobolev function spaces related to conical open bounded sets of Rn, n ≥ 1
Groundwater Resources Pollution Risk: Application of the Holman Method
No full textProblem statement: The aim of this study is to make an attempt to assess, through the application of the Holman Method, the effects that a careless management of human induced activities could have on aquifers and in particular on tapping wells used for human supply. Approach: The study had been applied to two different territories, as far as both the geomorphological and human induced aspects are concerned: the city of Aosta, the capital city of the Autonomous Aosta Valley region and three municipalities located in the centre of the Veneto region. Results: Thanks to the first results that had been obtained from the application of this method and other ones, it is hoped that a strategic territorial management approach will be adopted in the future so that the Groundwater Resources (GWR) can coexist with the economic and urban developments. Conclusion: All the analysis had been implemented utilizing a Geographical Information System (GIS
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
Analisi molecolare per l'endopoligalatturonasi in Pyrenophora graminea
No full textPyrenophora graminea Ito e Kuribayashi è un fungo ascomicete agente della striatura bruna dell’orzo e tipicamente trasmesso per seme. Le conoscenze sui meccanismi patogenetici di P.graminea sono relative esclusivamente alla produzione di composti fitotossici coinvolti nello sviluppo e nella intensità dei sintomi; sono noti, infatti, uno o più composti capaci di indurre sintomi tipici quando infiltrati in foglie di orzo (Haegi et al., 1994). Nell’ambito di una ricerca il cui intento è quello di fornire informazioni sulle basi genetico-molecolari della patogenicità, è stata intrapresa un’indagine sulla presenza ed espressione di geni per l’endo-poligalatturonasi in P.graminea. L’endo-poligalatturonasi (endo-PG) prodotta dai funghi svolge un ruolo importante nella degradazione delle pareti cellulari delle piante, digerendo i componenti pectici della lamella mediana e della parete primaria. La produzione di poligalatturonasi è generalmente sottoposta ad induzione da parte del substrato e a repressione da parte di fonti di carbonio preferenziali, quali ad esempio il glucosio. In alcuni casi però, come in Cochliobolus heterostrophus e in Aspergillus flavus, la sintesi di endo-PG non è repressa dal glucosio (Bateman et al., 1973; Whitehead, 1995). Questo enzima è spesso prodotto in forme molecolari multiple, sia in coltura che durante l’infezione della pianta, con differenti proprietà biochimiche e fisiologiche (Favaron e Marciano, 1992).
In prove preliminari, condotte con saggi enzimatici in piastra, era stata verificata la presenza di attività poligalatturonasica in diversi ceppi di P.graminea; per appurare un eventuale coinvolgimento delle poligalatturonasi nella patogenicità di questo fungo, si è deciso, quindi, di condurre un analisi molecolare di espressione utilizzando, come sonde, geni eterologhi dell’endo-PG clonati (Scott-Craig et al., 1990; Caprari et al., 1993). Come confronto è stato analizzato in alcuni esperimenti anche un ceppo di P.teres.
Le sonde pCC2 e pCC33, relative al gene dell’endo-PG rispettivamente di Fusarium moniliforme e di Cochliobolus carbonum, sono state inizialmente utilizzate sul DNA genomico di un ceppo di P.graminea (Pg2) e di uno di P.teres (Pt4); il risultato degli esperimenti di Southern blot ha dimostrato che le due sonde risconoscono una sequenza genomica in entrambe Pg2 e Pt4.
Si è quindi proceduto all’analisi dell’espressione dell’endo-PG nei due ceppi, mantenuti in coltura liquida in condizioni induttive e non (pectina; pectina e saccarosio in diverse proporzioni; saccarosio). Gli esperimenti di Northern blot hanno evidenziato in ambedue i ceppi un segnale di espressione, non molto intenso data l’eterologia della sonda, senza differenze significative tra i mezzi utilizzati.
Nel tentativo di isolare il gene omologo dell’endo-PG di P.graminea e di P.teres, sono stati effettuati esperimenti di PCR, utilizzando oligonucleotidi sintetizzati sulla base della sequenza genica clonata in F.moniliforme. Da entrambi i ceppi di Pyrenophora è stato ottenuto un prodotto di PCR con peso molecolare compatibile con quello atteso per il gene dell’endo-PG. I due frammenti (Pg2-PCR e Pt4-PCR) sono stati quindi riutilizzati come sonde omologhe in esperimenti di Southern blot e Northern blot.
i) Le due sonde omologhe (Pg2-PCR e Pt4-PCR) utilizzate in esperimenti di Southern-blot, effettuati su i due DNA genomici (Pg2 e Pt4) tagliati con enzimi di restrizione diversi, hanno presentato profili di ibridazione simili.
ii) Gli esperimenti di Northern-blot hanno evidenziato una espressione di endo-PG, apparentemente indipendente dai mezzi di coltura, il cui andamento è costante con entrambe le sonde.
In conclusione i prodotti di PCR, ottenuti dai genomi dei due ceppi Pg2 e Pt4, rappresentano una parte del gene dell’endo-PG di Pyrenophora; essi costituiscono, così, uno strumento più sensibile per una analisi fine di espressione con sonde omologhe, ma soprattutto, consentiranno uno studio strutturale del gene dell’endo-PG in P.graminea e in P.teres.
Al momento sono in corso esperimenti che estendono nel tempo l’analisi di espressione (campioni mantenuti in coltura su tre mezzi diversi: pectina 1% e saccarosio 0,2%; pectina 1% e saccarosio 1,2%; saccarosio 1,2%; tutti con 6 tempi d’induzione) ed in parallelo, sui filtrati colturali degli stessi campioni esaminati, vengono effettuati saggi di attività enzimatica.
Le ricerche proseguiranno per accertare la reale importanza dell’endo-PG nell’interazione P.graminea/orzo, confrontando l’andamento dell’espressione osservato su mezzi di crescita contenenti pectina commerciale con quello ottenuto per colture cresciute su estratti di pianta e con quello osservabile direttamente nella pianta infetta
The efficient identification of horizontal meandering in raw ultrasonic anemometer data
No full textThis paper shows a new experimental method for the detection and identification of sub-mesoscale low-frequency components, in particular horizontal meandering, in raw data from three-axial ultrasonic anemometers and other high resolution, high sampling-rate three-dimensional wind sensors. The proposed method is a combination of autocorrelation-based detection and FFT-based filtering, well known in literature. The results of the application of the described method to a sample of hourly raw data files are shown as well. The method can be used as a building block for eddy covariance and other data processing procedures as well as in all the situations where very short time scales (about 10s) are relevant, such as in odour or toxic chemical dispersion
Waste paper as carbohydrate source for biofuel production: An experimental investigation
No full textTHE LACK OF INHIBITION OF CLAVICEPS PURPUREA POLYGALACTURONASES BY PvPGIP2 MAY EXPLAIN THE FAILURE OF TRANSGENIC WHEAT PLANTS TO RESIST TO THE ERGOT PATHOGEN
No full textClaviceps purpurea is a biotrophic fungal pathogen of cereals
and grasses, attacking exclusively young ovaries. C. purpurea
grows intercellularly in rye (Secale cereale) ovaries by degrading
the pectic polymers and the fungal polygalacturonase (PG) has
been shown to be a pathogenicity factor. Two pg genes of C. purpurea,
cppg1 and cppg2, are responsible for this activity. Transgenic
plants expressing a bean polygalacturonase-inhibiting protein
(PvPGIP2) proved to be a valuable tool to increase resistance
against PG-producing fungi. However, a stable transgenic
PvPGIP2 wheat line, previously shown to be more resistant to
the fungal pathogens Bipolaris sorokiniana and Fusarium graminearum,
exhibited only a very low reduction of symptoms after infection
with C. purpurea. To understand whether this reduced
protection of PvPGIP2 in wheat transgenic plants was ascribable
to a lack of inhibition against the fungal PGs, we tried to perform
inhibition experiments against the C. purpurea PG activity. Unfortunately,
this fungus does not produce any PG activity in culture,
thus it was necessary to express this activity in a Pichia pastoris
heterologous system. The two heterologous expressed PGs,
when assayed against the PvPGIP2, were poorly affected by this
inhibitor, indicating that the lack of resistance in transformed
wheat line may be due to the lack of recognition of the PGs of C.
purpurea by PvPGIP2. This finding supports a role of PGIP in
plant defence only when PG-PGIP interaction occurs. The expressed
PGs may be useful to identify more effective PGIPs by a
broad screening of plant PGIPs
SNF1 protein kinase is important for growth and full virulence of Botrytis cinerea.
No full textAt early stages of infection, Botrytis cinerea secretes a wide spectrum of plant cell wall degrading enzymes (CWDEs) to facilitate penetration into host. So far, only the polygalacturonases PG1 and PG2 and the xylanase XYN11A were proved by reverse genetics to be required for virulence. Verification of the function of single members of the different CWDE classes is indeed difficult, due to gene redundancy in multigenic families.
In various plant pathogenic fungi, production of these enzymes is under catabolic repression and positively regulated by the snf1 (sucrose non-fermenting 1) gene which is expressed when glucose is depleted.
To examine the function of the snf1 gene in B. cinerea, knock-out mutants were obtained by targeted mutagenesis. The growth of the Δsnf1 mutants was compared with the wild type strain on minimal medium enriched with different simple and complex carbon sources (fructose, sucrose, glucose, xylan, xylose, pectin, polygalacturonic acid, cellulose). A significant reduction of growth was observed on some carbon sources except with glucose and xylan. Microscopic studies verified, that the sporulation of the mutants was almost abolished and unusually shaped mycelia were found. Pathogenicity tests performed on apple fruits displayed a strong defect in colonization by the Δsnf1 mutants with a 60% decrease in virulence.
Pathogenicity tests on plant systems are in progress together with the characterization of possible effects on secretion and expression of CWDEs
Fusarium 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
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