Showing papers on "Chitinase published in 1998"
TL;DR: In this article, it was shown that a single amino acid substitution in the catalytic center of the 39-kDa isoform of chitotriosidase, which generates a similar sequence to that in HC gp-39, results in a loss of hydrolytic activity and creates the capacity to bind to chitin.
Abstract: In various mammals, enzymatically active and inactive members of family 18 glycosyl hydrolases, containing chitinases, have been identified. In man, chitotriosidase is the functional chitinolytic enzyme, whilst the homologous human cartilage 39-kDa glycoprotein (HC gp-39) does not exhibit chitinase activity and its function is unknown. This study establishes that HC gp-39 is a chitin-specific lectin. It is experimentally demonstrated that a single amino acid substitution in the catalytic centre of the 39-kDa isoform of chitotriosidase, which generates a similar sequence to that in HC gp-39, results in a loss of hydrolytic activity and creates the capacity to bind to chitin. The possible implication of the finding for chitinolytic and chitin-binding proteins that are produced in high quantities by activated macrophages are discussed.
357 citations
TL;DR: This study shows that C. violaceum produces a set of chitinolytic enzymes whose production is regulated by HHL, and finds that a pleiotropic mini-Tn5 mutant of C. Violaceum that is defective in HHL production and other quorum-sensing-regulated factors was found to be completely deficient in chitinase activity.
Abstract: Quorum sensing control mediated by N-acyl homoserine lactone (AHL) signaling molecules has been established as a key feature of the regulation of exoenzyme production in many gram-negative bacteria. In Chromobacterium violaceum ATCC 31532 a number of phenotypic characteristics, including production of the purple pigment violacein, hydrogen cyanide, antibiotics, and exoproteases are known to be regulated by the endogenous AHL N-hexanoyl-l-homoserine lactone (HHL). In this study we show that C. violaceum produces a set of chitinolytic enzymes whose production is regulated by HHL. The chitinolytic activity was induced in strains grown in the presence of chitin as the sole carbon source and quantitated in the secreted proteins by using p-nitrophenol analogs of disaccharide, trisaccharide, and tetrasaccharide oligomers of N-acetylglucosamine. By using 4-methylumbelliferyl analogs of the same oligomers of N-acetylglucosamine as substrates for proteins separated and renatured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, at least six enzymes were detected: a chitobiase with high specificity to a dimeric substrate of 87 kDa, two N-acetylglucosaminidases with apparent molecular masses of 162 and 133 kDa, two endochitinases of 108 and 67 kDa, and a chitobiosidase of 56 kDa. In addition, two unidentified bands of >205 kDa were found where a tetrameric chitin derivative was used as a substrate. A pleiotropic mini-Tn5 mutant of C. violaceum (CV026) that is defective in HHL production and other quorum-sensing-regulated factors was also found to be completely deficient in chitinolytic activity. Growth of this mutant on minimal medium with chitin supplemented with culture supernatant from the C. violaceum wild-type strain or 10 μM synthetic HHL restored chitinase production to the level shown by the parental strain. These results constitute the most complete evidence so far for regulation of chitinolytic activity by AHL signaling in a gram-negative bacterium.
264 citations
TL;DR: Accumulation of these proteins, in combination with sugars, appears to constitute a novel, developmentally regulated defense mechanism against phytopathogens in the maturing fruit.
Abstract: During ripening of grape (Vitis labruscana L. cv Concord) berries, abundance of several proteins increased, coordinately with hexoses, to the extent that these became the predominant proteins in the ovary. These proteins have been identified by N-terminal amino acid-sequence analysis and/or function to be a thaumatin-like protein (grape osmotin), a lipid-transfer protein, and a basic and an acidic chitinase. The basic chitinase and grape osmotin exhibited activities against the principal grape fungal pathogens Guignardia bidwellii and Botrytis cinerea based on in vitro growth assays. The growth-inhibiting activity of the antifungal proteins was substantial at levels comparable to those that accumulate in the ripening fruit, and these activities were enhanced by as much as 70% in the presence of 1 M glucose, a physiological hexose concentration in berries. The simultaneous accumulation of the antifungal proteins and sugars during berry ripening was correlated with the characteristic development of pathogen resistance that occurs in fruits during ripening. Taken together, accumulation of these proteins, in combination with sugars, appears to constitute a novel, developmentally regulated defense mechanism against phytopathogens in the maturing fruit.
216 citations
TL;DR: In soil samples, NAGase activity was significantly correlated with estimates of fungal biomass, based on the content of two fungus-specific indicator molecules, 18:2ω6 phospholipid fatty acid (PLFA) and ergosterol.
Abstract: The determination of enzyme activities is a simple approach to the study of microbially mediated processes within the soil environment. Thus, soil enzyme activities have been interpreted as indirect measures of microbial biomass, rhizosphere effects, soil productivity, and mineralization potential of naturally occurring substrates or xenobiotics (4). However, few studies have attempted to correlate soil enzyme activities with the presence and activities of specific components of the microbial community. The ability of soil-inhabiting fungi to produce a range of enzymes capable of degrading complex litter substances could make the use of an enzymatic approach to study soil fungal populations possible. These enzymes must be specific for fungal presence and activity. In one study of chitinase in soil (24), chitinase activity and the number of fungal propagules in chitin-amended soils were strongly correlated. The same correlation was not found for actinomycetes or bacteria. Thus, chitinase activity appears to be a suitable indicator of actively growing fungi in the soil. The hydrolysis of cellulose requires the interaction of a number of hydrolases produced by cellulolytic microorganisms. A major role is played by the cellulase system, which consists of several distinct enzymes that are produced by a large number of microorganisms, including fungi, actinomycetes, and bacteria. However, fungi have been suggested as the predominant source of β-d-glucosidase (EC 3.2.1.21) (16, 17) and endo 1,4-β-glucanase (EC 3.2.1.4) (23) activity in soils.
Fluorogenic 4-methylumbelliferyl (MUF)-labelled enzyme substrates have been introduced for process-oriented studies in aquatic systems (3, 18) and, more recently, in peatlands (11). MUF substrates have been used to assay cell-bound activities in pure cultures of fungi, as the soluble substrate can enter the cell wall, making periplasmic enzyme activity detectable (15). These substrates have been used to detect fungal chitinolytic activities (17a) and cellulases (6) in vitro. The substrates may be added to environmental samples and, when hydrolyzed, release 4-methyl-umbelliferone (4-MU), which fluoresces and can be quantified in nanomolar concentrations (3).
A variety of methods to quantify fungi in soil have been described. The techniques include direct microscopic observation and extraction of fungus-specific indicator molecules such as glucosamine or ergosterol (9). More recently, the phospholipid fatty acid (PLFA) 18:2ω6 has been proposed as an indicator of fungal biomass (7, 12). Our objectives in the present study were to determine if (i) components of chitinase and cellulase activities could be used as indicators of the presence and activity of fungal biomass and (ii) enzyme activities detected with specific MUF substrates in soil samples were correlated with the content of the fungus-specific indicator molecules 18:2ω6 PLFA and ergosterol.
200 citations
TL;DR: Three transgenic cucumber strains showed the highest resistance against B. cinerea: the spread of disease was inhibited completely in these strains, which would serve as good breeding materials for disease resistance.
Abstract: A rice chitinase cDNA (RCC2) driven by the CaMV 35S promoter was introduced into cucumber (Cucumis sativus L.) through Agrobacterium mediation. More than 200 putative transgenic shoots were regenerated and grown on MS medium supplemented with 100 mg/l kanamycin. Sixty elongated shoots were examined for the presence of the integrated RCC2 gene and subsequently confirmed to have it. Of these, 20 were tested for resistance against gray mold (Botrytis cinerea) by infection with the conidia: 15 strains out of the 20 independent shoots exhibited a higher resistance than the control (non-transgenic plants). Three transgenic cucumber strains (designated CR29, CR32 and CR33) showed the highest resistance against B. cinerea: the spread of disease was inhibited completely in these strains. Chitinase gene expression in highly resistant transgenic strains (CR32 and CR33) was compared to that of a susceptible transgenic strain (CR20) and a control. Different responses for disease resistance were observed among the highly resistant strains. CR33 inhibited appressoria formation and penetration of hyphae. Although CR32 permitted penetration of hyphae, invasion of the infection hyphae was restricted. Furthermore, progenies of CR32 showed a segregation ratio of 3:1 (resistant:susceptible). As the disease resistance against gray mold was confirmed to be inheritable, these highly resistant transgenic cucumber strains would serve as good breeding materials for disease resistance.
192 citations
TL;DR: Both budworm and hornworm larvae, when fed on chitinase-expressing transgenic plants coated with sublethal concentrations of a Bacillus thuringiensis toxin, were significantly stunted relative to larvae fed on toxin-treated non-transgenic controls.
Abstract: Chitinase expression in the insect gut normally occurs only during moulting, where the chitin of the peritrophic membrane is presumably degraded. Thus, insects feeding on plants that constitutively express an insect chitinase gene might be adversely affected, owing to an inappropriately timed exposure to chitinase. This hypothesis was tested by introducing a cDNA encoding a tobacco hornworm (Manduca sexta) chitinase (EC 3.2.1.14) into tobacco via Agrobacterium tumefaciens-mediated transformation. A truncated but enzymatically active chitinase was present in plants expressing the gene. Segregating progeny of high-expressing plants were compared for their ability to support growth of tobacco budworm (Heliothis virescens) larvae and for feeding damage. Both parameters were significantly reduced when budworms fed on transgenic tobacco plants expressing high levels of the chitinase gene. In contrast, hornworm larvae showed no significant growth reduction when fed on the chitinase-expressing transgenics. However, both budworm and hornworm larvae, when fed on chitinase-expressing transgenic plants coated with sublethal concentrations of a Bacillus thuringiensis toxin, were significantly stunted relative to larvae fed on toxin-treated non-transgenic controls. Foliar damage was also reduced. Plants expressing an insect chitinase gene may have agronomic potential for insect control.
183 citations
TL;DR: An inoculation procedure was developed to obtain efficient and synchronous infection on detached tomato leaves by Botrytis cinerea and Tomato PR protein mRNAs were induced during the infection, albeit with different kinetics and to different levels.
Abstract: An inoculation procedure was developed to obtain efficient and synchronous infection on detached tomato leaves by Botrytis cinerea. In spray-inoculated leaves incubated at 20 °C, the infection process consisted of three phases: the formation of primary necrotic lesions (until 20 hpi), a quiescent phase (20-72 hpi), and the expansion of a proportion of the primary lesions (from 72 hpi onwards), resulting in full tissue maceration. At 4 °C, the infection progressed slowly but steadily without inducing necrotic responses in the host. The actin and β-tubulin genes of B. cinerea were cloned, characterized and used as probes on blots containing RNAs from leaves at various stages of the infection. The genes displayed a similar expression pattern throughout the infection and the hybridization signal reflected the amount of fungal biomass. The actin mRNA accumulated to higher levels than the β-tubulin mRNA. Tomato PR protein mRNAs (chitinase, β-1,3-glucanase and PR-1) were induced during the infection, albeit with different kinetics and to different levels. At 20 °C, β-1,3-glucanase and PR-1 mRNAs were induced more rapidly than chitinase mRNAs. At 4 °C, mRNAs encoding extracellular β-1,3-glucanase and intracellular, as well as extracellular chitinase were hardly induced.
183 citations
TL;DR: It is proposed that the alkalinity of infected cuticle represents a physiological signal that triggers the production of virulence factors and played a major role in gene expression of secreted proteins.
Abstract: Secretion of proteolytic and chitinolytic enzymes is a hallmark of infection processes of Metralhizium anisopliae in response to host (insect) cuticular signals. The regulation of these enzymes (subtilisin-like proteases [Pr1a and Pr1b], trypsin-like proteases [Pr2], metalloproteases, aspartyl proteases, aminopeptidase, and chitinases) and a hydrophobin was investigated by Northern analysis and/or enzyme assay. The production of each enzyme showed a differential expression pattern in response to ambient pH; enzymes were synthesized only at pHs at which they function effectively, irrespective of whether the medium contained an inductive cuticle substrate. Three aspartyl proteases (pH optimum, 3), and chitinase (pH optimum, 5) showed maximal accumulation at acidic pHs. The highest level of aminopeptidase (pH optimum, 7) was detected at pH 7. The highest levels of five metalloproteases (pH optima, ca. 7) were detected over the pH range 6 to 8. Two trypsins and several subtilisin-like Pr1 isoforms with pH optima of ca. 8 were produced only under alkaline conditions. Northern analysis of RNA species corresponding to seven cDNA sequences encoding proteases and chitinase confirmed that the ambient pH played a major role in gene expression of secreted proteins. Hydrophobin was expressed almost equally at pHs 5 and 8 but was not expressed at pH 3. During fungal penetration, the pH of infected cuticle rises from about 6.3 to 7.7. Consistent with pH regulation of enzyme production, serine and metalloproteases were produced in situ during infection, but no production of aspartyl proteases was found. We propose that the alkalinity of infected cuticle represents a physiological signal that triggers the production of virulence factors.
177 citations
TL;DR: Ag-Aper1 is the first cloned PM gene from a disease vector and is likely to act as a molecular linker that connects PM chitin fibrils into a three-dimensional network.
175 citations
TL;DR: A potential for biological control of diseases caused by P. infestans was also suggested by strain YCED-9’s strong in vitro antagonism towards pathogenic isolates of this fungus.
Abstract: strain YCED-9 is an antifungal biocontrol agent antagonistic to many different classes of plant pathogenic fungi. We discovered that strain YCED-9 produces three antimicrobial compounds with antifungal activity. These compounds were purified and identified, and included: AFA (Anti-Fusarium Activity), a fungicidal complex of polyene-like compounds similar to guanidylfungin A and active against most fungi except oomycetes; nigericin, a fungistatic polyether; and geldanamycin, a benzoquinoid polyketide highly inhibitory of mycelial growth of Pythium and Phytophthora spp. Antimicrobial assays were developed to estimate the production of each antibiotic independently. Medium composition had differential effects on the production of each metabolite. The hydrolytic enzymes chitinase and β-1,3-glucanase are also produced under induction by colloidal chitin and laminarin, respectively. Fungal cell walls induced the production of both enzymes. A potential for biological control of diseases caused by P. infestans was also suggested by strain YCED-9’s strong in vitro antagonism towards pathogenic isolates of this fungus.
172 citations
TL;DR: It appeared that in many cases the inhibition of fungal growth was not accompanied by bacterial chitinase production, which may indicate that antibiotics were involved in the antagonistic activities of chitinolytic bacteria against fungi.
Abstract: Anti-fungal properties of chitinolytic soil bacteria may enable them to compete successfully for chitin with fungi Additionally, the production of chitinase may be part of a lytic system that enables the bacteria to use living hyphae rather than chitin as the actual growth substrate, since chitin is an important constituent of most fungal cell walls Lysis of living fungal hyphae by chitinolytic bacteria has been reported frequently; however, these reports nearly always deal with bacteria that had been selected because of their mycolytic properties Our main objective was to get a better understanding of the relationship between chitinolytic and anti-fungal properties of bacteria that occur naturally in soils, ie without artificial selection Three inner dune sites, two of which were lime-poor and one lime-rich, along the Dutch coast were selected for this study Bacteria that were able to degrade colloidal chitin in water–agar comprised 02–57% of the total amount of culturable bacteria of these dune sites Pseudomonas spp were the most abundant culturable, chitin-degrading bacteria at the lime-poor sites, whereas Xanthomonas spp and Cytophaga spp were important at the lime-rich site Chitinolytic actinomycetes were relatively abundant at all three sites Chitinolytic and non-chitinolytic bacteria were randomly selected and tested for the possession of antagonistic activities against fungal dune strains [ Chaetomium globosum , Fusarium culmorum , F oxysporum , Idriella (Microdochium) bolleyi , Mucor hiemalis , Phoma exigua , Ulocladium sp] The tests were done using water–agar to simulate the energy-limiting conditions that bacteria will encounter in dune soils The percentage of bacterial isolates that were antagonistic against these fungi was considerably higher for chitinolytic strains than for non-chitinolytic ones Therefore, the possible involvement of chitinase with respect to the inhibition of fungal growth was studied in more detail It appeared that in many cases the inhibition of fungal growth was not accompanied by bacterial chitinase production There was also no clear relationship between the activity of other cell wall degrading enzymes ( β -1,3-glucanase and protease) and antagonism Chitinolytic bacteria had selective rather than general anti-fungal properties, which were not necessarily related to differences in general susceptibility of the fungi towards antagonism These results may indicate that antibiotics were involved in the antagonistic activities of chitinolytic bacteria against fungi Only growing fungi were antagonized by the chitinolytic bacteria; none of the chitinolytic bacteria were able to lyse existing mycelium of any of the fungi The relevance of the results for the ecology of chitinolytic soil bacteria is discussed
TL;DR: Results showed that much higher concentrations of bacteria were required to achieve even low mortalities, and addition of chitinase A gave no increase in death rate, demonstrating a role for bacterial chit inases in the attack on the insects.
Abstract: Bacillus thuringiensis subsp. israelensis IPS78 and B. thuringiensis subsp. aizawai HD133 both secreted exochitinase activity when grown in a medium containing chitin. Allosamidin, a specific chitinase inhibitor, inhibited activity from both strains, with IC50 values of about 50 μM with colloidal chitin as substrate and between 1 and 10 μM with 4-methylumbelliferyl-diacetylchitobioside and 4-methylumbelliferyl-triacetylchitotrioside as substrates. The involvement of these chitinolytic activities during pathogenesis in insects has been investigated with B. thuringiensis subsp. israelensis IPS78 against larvae of the midge Culicoides nubeculosus, and with B. thuringiensis subsp. aizawai HD133 against caterpillars of the cotton leafworm Spodoptera littoralis. Presence of 100 μM allosamidin increased the LD50 by factors of 1.3 and 1.4, respectively, demonstrating a role for bacterial chitinases in the attack on the insects. Presence of chitinase A from Serratia marcescens considerably decreased the values for LD50' confirming previous observations with different systems of the potentiation of entomopathogenesis of B. thuringiensis by exogenous chitinases. The most likely action of the endogenous chitinases of B. thuringiensis is to weaken the insects' peritrophic membranes, allowing more ready access of the bacterial toxins to the gut epithelia. Addition of exogenous chitinases will then increase this effect. Complementary cross-infection experiments, strain HD133 against midge larvae and strain IPS78 against caterpillars, were performed to investigate the pathogen/host specificities of the effects. Results showed that much higher concentrations of bacteria were required to achieve even low mortalities, and addition of chitinase A gave no increase in death rate.
TL;DR: Data indicate that the 10 tobacco chitinases represent complementary enzymes which may have synergistic effects on their substrates and their implication in plant defense by attacking pathogen's structural components and in plant development by maturing signal molecules is discussed.
Abstract: Ten tobacco chitinases (1,4-N-acetyl-beta-D-glucosaminide glycanhydrolase, EC 3.2.1.14) were purified from tobacco leaves hypersensitively reacting to tobacco mosaic virus. The 10 enzymes, which belong to five distinct structural classes of plant chitinases, were incubated with several potential substrates such as chitin, a beta-1,4 N-acetyl-D-glucosamine (GlcNAc) polymer, chitosan (partially deacetylated chitin), chitin oligomers of variable length and bacterial cell wall. Tobacco chitinases are all endotype enzymes that liberate oligomers from chitin and are capable of processing the chito-oligomers further at differential rates. Chitin reaction products were separated and quantified by HPLC and differential kinetics of oligomer accumulation and degradation were observed with the distinct classes of chitinases. Depending on the substrate to be hydrolysed, each isoform displayed a different spectrum of activity. For example, class I isoforms were the most active on chitin and (GlcNAc)4-6 whereas class III basic isoforms were the most efficient in inducing bacterial lysis. Class V and class VI chitinases were shown to more readily hydrolyse chitin oligomers than the chitin polymer itself. Together, these data indicate that the 10 tobacco chitinases represent complementary enzymes which may have synergistic effects on their substrates. This paper discusses their implication in plant defense by attacking pathogen's structural components and in plant development by maturing signal molecules.
TL;DR: Comparison of the amino acid sequence of the deduced polypeptide with that of other proteins showed that CBP21 is similar (45.3% amino acid identity) to CHB1 of Streptomyces olivaceoviridis, suggesting a wide distribution of this type of chitin binding protein in chitinolytic microorganisms.
Abstract: A chitin binding protein (CBP21) 21 kDa in size, is a major protein in the culture supernatant when Serratia marcescens 2170 is grown in the presence of chitin. The gene (cbp) for CBP21 was found to be located in a region 1.5 kb downstream of the chiB gene encoding chitinase B. The cbp gene encodes a polypeptide of 197 amino acids with a calculated size of 21.6 kDa containing a putative signal sequence of 27 amino acids. Comparison of the amino acid sequence of the deduced polypeptide with that of other proteins showed that CBP21 is similar (45.3% amino acid identity) to CHB1 of Streptomyces olivaceoviridis. Purified CBP21 prepared from the periplasmic fraction of Escherichia coli carrying the cloned cbp gene showed its highest binding activity to squid chitin (β-chitin) followed by colloidal chitin and regenerated chitin. Binding of CBP21 to regenerated chitin was affected by pH, in particular, low pH reduced binding activity markedly.The presence of similar chitin binding proteins in the distantly relat...
TL;DR: The results from these experiments indicated that chitinase of F. chlamydosporum plays an important role in the biocontrol of groundnut rust.
Abstract: Chitinase (EC 3.2.1.14) was isolated from the culture filtrate of Fusarium chlamydosporum and purified by ion-exchange chromatography and gel filtration. The molecular mass of purified chitinase wa...
TL;DR: A molecule that is resistant to heat and protease treatment, obtained from Rhizoctonia solani cell walls induces expression of both genes and is involved in the regulation of the expression of hydrolytic enzymes during mycoparasitism by T. harzianum.
Abstract: The mycoparasite Trichoderma harzianum has been extensively used in the biocontrol of a wide range of phytopathogenic fungi. Hydrolytic enzymes secreted by the parasite have been directly implicated in the lysis of the host. Dual cultures of Trichoderma and a host, with and without contact, were used as means to study the mycoparasitic response in Trichoderma. Northern analysis showed high-level expression of genes encoding a proteinase (prb1) and an endochitinase (ech42) in dual cultures even if contact with the host was prevented by using cellophane membranes. Neither gene was induced during the interaction of Trichoderma with lectin-coated nylon fibres, which are known to induce hyphal coiling and appressorium formation. Thus, the signal involved in triggering the production of these hydrolytic enzymes by T. harzianum during the parasitic response is independent of the recognition mediated by this lectin-carbohydrate interaction. The results showed that induction of prb1 and ech42 is contact-independent, and a diffusible molecule produced by the host is the signal that triggers expression of both genes in vivo. Furthermore, a molecule that is resistant to heat and protease treatment, obtained from Rhizoctonia solani cell walls induces expression of both genes. Thus, this molecule is involved in the regulation of the expression of hydrolytic enzymes during mycoparasitism by T. harzianum.
TL;DR: Other properties of the strain, such as the formation of endospores, the presence of meso-diaminopimelic acid in the cell wall, the percent G+C of DNA, and the partial 16S ribosomal DNA sequence indicated that strain MH-1 should belong to the genus Bacillus.
Abstract: A thermophilic and actinic bacterium strain, MH-1, which produced three different endochitinases in its culture fluid was isolated from chitin-containing compost. The microorganism did not grow in any of the usual media for actinomyces but only in colloidal chitin supplemented with yeast extract and (2, 6-O-dimethyl)-beta-cyclodextrin. Compost extract enhanced its growth. In spite of the formation of branched mycelia, other properties of the strain, such as the formation of endospores, the presence of meso-diaminopimelic acid in the cell wall, the percent G+C of DNA (55%), and the partial 16S ribosomal DNA sequence, indicated that strain MH-1 should belong to the genus Bacillus. Three isoforms of endochitinase (L, M, and S) were purified to homogeneity and characterized from Bacillus sp. strain MH-1. They had different molecular masses (71, 62, and 53 kDa), pIs (5.3, 4.8, and 4.7), and N-terminal amino acid sequences. Chitinases L, M, and S showed relatively high temperature optima (75, 65, and 75 degreesC) and stabilities and showed pH optima in an acidic range (pH 6.5, 5.5, and 5.5, respectively). When reacted with acetylchitohexaose [(GlcNAc)6], chitinases L and S produced (GlcNAc)2 at the highest rate while chitinase M produced (GlcNAc)3 at the highest rate. None of the three chitinases hydrolyzed (GlcNAc)2. Chitinase L produced (GlcNAc)2 and (GlcNAc)3 in most abundance from 66 and 11% partially acetylated chitosan. The p-nitrophenol (pNP)-releasing activity of chitinase L was highest toward pNP-(GlcNAc)2, and those of chitinases M and S were highest toward pNP-(GlcNAc)3. All three enzymes were inert to pNP-GlcNAc. AgCl, HgCl2, and (GlcNAc)2 inhibited the activities of all three enzymes, while MnCl2 and CaCl2 slightly activated all of the enzymes.
TL;DR: The introduction of disease defence genes into rose provides a method of producing blackspot-resistant rose cultivars sought by breeders and growers.
Abstract: Blackspot, caused by the Ascomycete fungus Diplocarpon rosae, is the most widespread and pernicious disease of cultivated roses. While some species of rose possess resistance to D. rosae, none of the modern-day rose cultivars are fully resistant to the pathogen. In the current study, Biolistic gene delivery was used to introduce a rice gene, encoding a basic (Class I), chitinase into embryogenic callus of the blackspot-susceptible rose (Rosa hybrida L.) cv. Glad Tidings. The plasmid used for transformation carried the neomycin phosphotransferase (nptII) gene facilitating the selection and regeneration of transgenic plants on medium containing 250 mg/l kanamycin. Southern analysis confirmed integration of 2–6 copies of the chitinase gene into the rose genome; gene expression was confirmed by enzyme assay. Bioassays demonstrated that expression of the chitinase transgene reduced the severity of blackspot development by 13–43%. This degree of resistance to the pathogen correlated with the level of chitinase expression in the transgenic rose plants. The introduction of disease defence genes into rose provides a method of producing blackspot-resistant rose cultivars sought by breeders and growers.
TL;DR: In situ staining of beta-galactosidase activity found high expression in metulae, phialides, and conidia during conidiophore development, indicating that the expression of chiA is developmentally regulated.
Abstract: We cloned a chitinase-encoding gene from Aspergillus nidulans by polymerase chain reaction using degenerated oligonucleotide primers designed from the conserved amino acid sequences among chitinases from yeasts and Rhizopus spp. The cloned gene, named chiA, encoded a polypeptide consisting of 660 amino acids. Disruption of chiA had no effect on hyphal or conidiophore morphology, but germination frequency and hyphal growth rate decreased substantially. Expression of chiA was investigated using Escherichia coli β-galactosidase as a reporter enzyme. The β-galactosidase activity was present during hyphal growth and increased twice as the conidiophores developed. In situ staining of β-galactosidase activity found high expression in metulae, phialides, and conidia during conidiophore development, indicating that the expression of chiA is developmentally regulated. This is the first report to isolate a chitinase gene from A. nidulans and investigate its functions using the gene disruption technique and gene fusi...
TL;DR: Results indicate that peroxidase and chitinase may have a role in insect resistance in wheat cultivars containing the Dn-1 gene for resistance to the Russian wheat aphid Diuraphis noxia.
Abstract: The intercellular peroxidase and chitinase activities of three wheat cultivars [Triticum aestivum L. cvs `Tugela DN', `Molopo DN' (Gariep) and `Betta DN'] containing the Dn-1 gene for resistance to the Russian wheat aphid (RWA) Diuraphis noxia (Mordvilko) and the corresponding near-isogenic susceptible cultivars (`Tugela', `Molopo' and `Betta') were studied under conditions of infestation and non-infestation. The aim was to gain information on the mechanism of resistance. The resistance response was induced by RWA infestation. Infestation rapidly induced the activities of both enzymes selectively in resistant wheat to levels of magnitudes higher than those in susceptible wheat. The genetic background in which the Dn-1 resistance gene is bred played a role and the level of activity corresponded to the level of resistance. Immunologic studies confirmed that the induction of enzyme activities was due to the induction of higher protein levels. These results indicate that peroxidase and chitinase may have a role in insect resistance.
TL;DR: Native fluorescent pseudomonads isolated from the rhizosphere of Lotus corniculatus were screened in vitro for their antagonistic activity against the phytopathogenic fungi Pythium ultimum and Rhizoctonia solani and three Pseudomonas fluorescens strains were selected.
Abstract: Native fluorescent pseudomonads isolated from the rhizosphere of Lotus corniculatus were screened in vitro for their antagonistic activity against the phytopathogenic fungi Pythium ultimum and Rhizoctonia solani. About 12% of the bacterial isolates inhibited one or both fungi in vitro. Isolates which exhibited the greatest antagonistic activity were assayed in vivo against the pathogens. Three Pseudomonas fluorescens strains were selected from these assays: UP61, UP143 and UP148. These strains produced HCN and siderophores, but addition of iron to the medium did not affect the antagonistic activity. Lytic enzymes such as chitinase and β-1,3-glucanase were not detected. The simultaneous inoculation of Pseudomonas strains and Rhizobium loti B816 did not affect nitrogen fixation efficiency in L. corniculatus plants. Sterile peat was successful as a carrier for these P. fluorescens strains.
TL;DR: Some diversity in the chitinase activities concerning New chitosanase acidic isoforms have been shown in substrate specificity in mycorrhizal plants, including tomato roots sanases colonized in vitro by Gigaspora rosea.
Abstract: Phytophthora-infected plants. These results suggest some diversity in the chitinase activities concerning New chitosanase acidic isoforms have been shown in substrate specificity in mycorrhizal plants. The Glomus mosseae-colonized tomato roots and their possible implications of these observations in the induction, together with the previously described functioning of the symbiosis is discussed. mycorrhiza-related chitinase isoform, has been further corroborated in plants colonized with another Glomus Key words: Arbuscular mycorrhizas, chitinases, chitospecies (G. intraradices), as well as in tomato roots sanases, Phytophthora parasitica, tomato, Lycopersicon colonized in vitro by Gigaspora rosea. The induction esculentum. of these chitosanase isoforms appears as a specific response to the arbuscular mycorrhizal (AM) symbiosis, and does not correspond to unspecific defence Introduction
TL;DR: Results indicate that the chitin-binding domain helps determine the movement of chit inase along N-acetylglucosamine strands and within environments containing chitIn.
Abstract: To examine the ecology and evolution of microbial chitinases, especially the chitin-binding domain, one of the chitinase genes (chiA) from the marine bacterium Vibrio harveyi was analysed. The deduced amino acid sequence of ChiA is not very similar overall to other proteins, except for two regions, the putative catalytic and chitin-binding domains. Among all bacterial chitinases sequenced to date, there is no relationship between percentage similarity of catalytic domains and chitin-binding domains in pairwise comparisons, suggesting that these two domains have evolved separately. The chitin-binding domain appears to be evolutionarily conserved among many bacterial chitinases and is also somewhat similar to cellulose-binding domains found in microbial cellulases and xylanases. To investigate the role of the chitin-binding domain, clones producing versions of ChiA with or without this domain were examined. One version with the domain (ChiA1) bound to and hydrolysed chitin, whereas a truncated ChiA without the putative chitin-binding domain (ChiA2) did not bind to chitin but it could hydrolyse chitin, although not as well. ChiA1 diffused more slowly in agarose containing colloidal chitin than ChiA2, but diffusion of the Two proteins in agarose without colloidal chitin was similar. These results indicate that the chitin-binding domain helps determine the movement of chitinase along N-acetylglucosamine strands and within environments containing chitin.
TL;DR: The results demonstrate that these two enzymes have antifungal activity against U. necator, and are consistent with these pathogenesis‐related proteins having a role in defence of grapevines against powdery mildew.
Abstract: Leaves were collected from 21 different grapevine (Vitis ssp.) genotypes with varying resistance to powdery mildew disease caused by Uncinula necator. For leaves collected from field‐grown vines in spring there was a correlation between resistance rating and activity of chitinase and β‐1,3‐glucanase. The correlation was greater with the sum of the two enzyme activities. In contrast, no correlation was obtained for leaves collected during summer. With leaves from glasshouse grown vines, wounding or infection with powdery mildew increased both chitinase and β‐1,3‐glucanase activity. Light microscope examination of detached leaves inoculated with U. necator conidia showed that germination appeared to occur at the same rate on leaves of a susceptible (Sultana) and a resistant (Seyval) genotype. Subsequent development of mycelia was severely restricted on the resistant genotype but it was prolific on the sensitive genotype. A bioassay was developed based on germination and extension of the germ tube of U. necator conidia on agar plates. Agar preparations containing desalted crude extracts of grapevine leaves inhibited growth and caused the tips of the hyphae to rupture. The effect was not observed with boiled extracts and was greater with extracts from resistant genotypes. Chitinase and β‐1,3‐glucanase were purified 760‐fold and 46‐fold respectively from leaves of Seyval grapevines. The purified enzyme preparations inhibited germ tube growth, with the effect being more prominent in the presence of both enzymes. The results demonstrate that these two enzymes have antifungal activity against U. necator, and are consistent with these pathogenesis‐related proteins having a role in defence of grapevines against powdery mildew.
TL;DR: Comparative sequence analysis of two chitinases from berries and two from wine demonstrated that, despite their reputed resistance to proteolytic degradation, some limited proteolytics processing of these proteins occurs.
Abstract: Chitinases account for ca. 50% of the soluble proteins in the berries of the grape vine (Vitis vinifera L. Muscat of Alexandria). The other major proteins present are thaumatin-like proteins. Both these groups of proteins persist through the vinification process and cause hazes and sediments in bottled wines. Four chitinases have been purified from Muscat of Alexandria fruit and characterized by both sequence and mass spectral analysis. Their protein sequences were highly similar, and all proteins were modified at their N-terminus. It was confirmed for three of the chitinases that the N-terminal group was a pyroglutamate residue. Comparative sequence analysis of two chitinases from berries and two from wine demonstrated that, despite their reputed resistance to proteolytic degradation, some limited proteolytic processing of these proteins occurs. The peptide fragments of the chitinases account for only 3% of the total soluble protein content of the fruit. Keywords: Pathogenesis related proteins; chitinase...
TL;DR: The complete nucleotide sequence and analysis of the chromosomal and full-length cDNA copies of the regulated gene (chit1) coding one of the chitinases produced by the biocontrol agent Metarhizium anisopliae are reported.
Abstract: There are no reports to date of entire gene sequences coding for chitinolytic enzymes from entomopathogenic fungi, even though these enzymes act synergistically with proteolytic enzymes to solubilize insect cuticle during the key step of host penetration, having considerable importance in the biological control of some insect pests. This paper reports the complete nucleotide sequence and analysis of the chromosomal and full-length cDNA copies of the regulated gene (chit1) coding one of the chitinases produced by the biocontrol agent Metarhizium anisopliae. Degenerated primers, encompassing conserved regions of other fungal chitinases, were used to amplify a 650-bp DNA fragment, which was used to isolate genomic and cDNA clones from M. anisopliae. Albeit at least two different chitinases are characterized in this fungus, only one chit gene was isolated. The chit1 gene is interrupted by three short typical fungal introns and has a 1,521-bp ORF, which encodes a protein of 423 amino acids with a stretch of 35 amino acid residues displaying characteristics of signal peptide. The deduced sequence of the mature protein predicts a 42-kDa protein with pI of 5.8. Southern analysis of genomic DNA indicates a single copy of chit1 in the M. anisopliae genome.
TL;DR: An alkalophilic, chit inase-producing Bacillus sp.
Abstract: An alkalophilic, chitinase-producing Bacillus sp. BG-11 was isolated which produced an extracellular chitinase and which was purified 16.5-fold, using standard purification techniques. The purified chitinase exhibited a broad pH and temperature optima of 7.5-9.0 and 45 deg C-55 deg C, respectively. The chitinase was stable between pH 6.0-9.0 and 50°C for more than 2 h. Half lives of enzyme at 60 deg C, 70 deg C and 80 deg C were 90 min, 30 min and 20 min respectively. Km value was 12 mg chitin per ml. Shelf life was 60 days at 4°C. Ca2+, Ni2+ and Triton-X-100 stimulated the activity up to 20% whereas Ag+, Hg2+, dithiothreitol, β-mercaptoethanol, glutathione, iodoacetic acid and iodoacetamide inhibited the activity up to 50%.
TL;DR: It is shown that accumulation of chitinases and β-1,3-glucanases could be stimulated by wounding the berry peduncle and inhibit the germination of conidia of Botrytis cinerea by 50% at a concentration of 7.5 μg ml -1 .
Abstract: In order to better understand the defense strategy of grape berries (Vitis vinifera L. cv. Pinot noir) as they mature, the activities of the defense-related proteins, chitinase (CHV, EC 3.2.1.14) and β-1,3-glucanase (laminarinase, EC 3.2.1.39) were first estimated in berries at different maturation stages. Chitinase levels rose proportionally to the berry reducing sugar content, an indicator of the berry ripening degree, up to values 10 times higher than the ones seen in resting grapevine leaves. This rise in activity was due to the accumulation of two isoforms, CHV 5 and CHV 11. One more chitinase isoform, CHV 12, appeared in senescent berries. Conversely, no glucanase activity could be detected in berries at any maturation stage. Accumulation of chitinases and β-1,3-glucanases could be stimulated by wounding the berry peduncle. Adding salicylic acid to the wounded berries only potentiated the wounding effect on the berry chitinase activity. The most active chitinase isoform, CHV 5. was purified to homogeneity. It represented about 40% of the total extractable protein content of a ripe berry. Its molecular mass was estimated to be 31 kDa. The peptide sequencing of four of its tryptic fragments revealed strong homologies to several class IV chitinases. Finally, it was shown to inhibit the germination of conidia of Botrytis cinerea by 50% at a concentration of 7.5 μg ml -1 .
TL;DR: Chitosan (1000 ppm) reduced germination of uredospores of Puccinia arachidis, the incitant of groundnut leaf rust disease and showed an increase in endogenous salicylic acid, intercellular chitinase and glucanase activity.