Engineering a recombinant chitinase from the marine bacterium Bacillus aryabhattai with targeted activity on insoluble crystalline chitin for chitin oligomer production

Chitin, an abundant polysaccharide in India, is primary by-product of the seafood industry. Efficiently converting chitin into valuable products is crucial. Chitinase, transforms chitin into chitin oligomers, holds significant industrial potential. However, the crystalline and insoluble nature of chitin makes the conversion process challenging. In this study, a recombinant chitinase from marine bacteria Bacillus aryabhattai was developed. This enzyme exhibits activity against insoluble chitin substrates, chitin powder and flakes. The chitinase gene was cloned into the pET 23a plasmid and transformed into E. coli Rosetta pLysS. IPTG induction was employed to express chitinase, and purification using Ni-NTA affinity chromatography. Optimal chitinase activity against colloidal chitin was observed in Tris buffer at pH 8, temperature 55°C, with the presence of 400 mM sodium chloride. Enzyme kinetics studies revealed a Vmax of 2000 μmole min-1 and a Km of 4.6 mg mL-1. The highest chitinase activity against insoluble chitin powder and flakes reached 875 U mg-1 and 625 U mg-1, respectively. The chitinase demonstrated inhibition of Candida albicans, Fusarium solani, and Penicillium chrysogenum growth. Thin Layer Chromatography (TLC) and LC-MS analysis confirmed the production of chitin oligomers, chitin trimer, tetramer, pentamer, and hexamer, from chitin powder and flakes using recombinant chitinase.

Effect of four chitinase genes on the female fecundity in Sogatella furcifera (Horváth)

BACKGROUND

The white-backed planthopper (WPH), Sogatella furcifera (Horváth), is a destructive rice pest with strong reproductive capacity. To gain insights into the roles of chitinases in the reproductive process of this insect species, this study represents the first-ever endeavor to conduct an in-depth exploration into the reproductive functions of four chitinase genes.

RESULTS

In this study, it was observed that four chitinase genes were expressed in female adults, with a relatively high expression level in the ovaries. SfCht2 and SfIDGF1 were highly expressed during later ovarian development. while SfENGase increased and then decreased with ovarian development. SfCht2, SfCht6-2 and SfENGase were highly expressed in fat body on the first and second days after eclosion, whereas SfIDGF1 highest on day 7. Compared with control group, Silencing four chitinase genes inhibited ovarian development and significantly shortened the oviposition period of S. furcifera, reducing egg-laying capacity but not affecting egg hatching. The detection demonstrated that the expression levels of SfVg, SfVgR and 70-90% juvenile hormone (JH) signaling pathway-related reproductive genes was significantly down-regulated. Moreover, SfCht6-2 and SfENGase significantly affected the expression levels of Target of Rapamycin (TOR) signaling pathway genes. SfENGase had the ability to impact nutrient signaling pathways and fatty acid metabolism, repressing vitellogenin synthesis and ultimately influencing ovarian development of S. furcifera.

CONCLUSIONS

Overall, this study provides insight into the function of chitinases in insect fecundity and is of great significance for enriching the cognition of insect chitinase function. They will become the suitable target genes for controlling the most destructive rice planthoppers. © 2023 Society of Chemical Industry.

Gene Cloning, Heterologous Expression, and In Silico Analysis of Chitinase B from Serratia marcescens for Biocontrol of Spodoptera frugiperda Larvae Infesting Maize Crops

Spodoptera frugiperda, the fall armyworm (FAW), is a highly invasive polyphagous insect pest that is considered a source of severe economic losses to agricultural production. Currently, the majority of chemical insecticides pose tremendous threats to humans and animals besides insect resistance. Thus, there is an urgent need to develop new pest management strategies with more specificity, efficiency, and sustainability. Chitin-degrading enzymes, including chitinases, are promising agents which may contribute to FAW control. Chitinase-producing microorganisms are reported normally in bacteria and fungi. In the present study, Serratia marcescens was successfully isolated and identified from the larvae of Spodoptera frugiperda. The bacterial strain NRC408 displayed the highest chitinase enzyme activity of 250 units per milligram of protein. Subsequently, the chitinase gene was cloned and heterologously expressed in E. coli BL21 (DE3). Recombinant chitinase B was overproduced to 2.5-fold, driven by the T7 expression system. Recombinant chitinase B was evaluated for its efficacy as an insecticidal bioagent against S. frugiperda larvae, which induced significant alteration in subsequent developmental stages and conspicuous malformations. Additionally, our study highlights that in silico analyses of the anticipated protein encoded by the chitinase gene (ChiB) offered improved predictions for enzyme binding and catalytic activity. The effectiveness of (ChiB) against S. frugiperda was evaluated in laboratory and controlled field conditions. The results indicated significant mortality, disturbed development, different induced malformations, and a reduction in larval populations. Thus, the current study consequently recommends chitinase B for the first time to control FAW.

The chitin-binding domain of Bacillus thuringiensis ChiA74 inhibits gram-negative bacterial and fungal pathogens of humans and plants

The chitinase ChiA74 is synthesized by Bacillus thuringiensis and possesses a modular organization composed of four domains. In the C-terminal of the enzyme is located the chitin-binding domain (CBD), which has not been isolated as a single unit or characterized. Here, we aimed to isolate the ChiA74's CBD as a single unit, determine the binding properties, and evaluate its antimicrobial and hemolytic activities. We cloned the ChiA74's CBD and expressed it in Escherichia coli BL21. The single domain was purified, analyzed by SDS-PAGE, and characterized. The recombinant CBD (rCBD) showed a molecular mass of ∼14 kDa and binds strongly to α-chitin, with Kd and Bmax of ∼4.7 ± 0.9 μM and 1.5 ± 0.1 μmoles/g chitin, respectively. Besides, the binding potential (Bmax/Kd) was stronger for α-chitin (∼0.31) than microcrystalline cellulose (∼0.19). It was also shown that the purified rCBD inhibited the growth of the clinically relevant Gram-negative bacteria (GNB) Vibrio cholerae, and V. parahemolyticus CVP2 with minimum inhibitory concentrations (MICs) of 121 ± 9.9 and 138 ± 3.2 μg/mL, respectively, and of one of the most common GNB plant pathogens, Pseudomonas syringae with a MIC of 230 ± 13.8 μg/mL. In addition, the rCBD possessed antifungal activity inhibiting the conidia germination of Fusarium oxysporum (MIC = 192 ± 37.5 μg/mL) and lacked hemolytic and agglutination activities against human erythrocytes. The significance of this work lies in the fact that data provided here show for the first time that ChiA74's CBD from B. thuringiensis has antimicrobial activity, suggesting its potential use against significant pathogenic microorganisms. Future works will be focused on testing the inhibitory effect against other pathogenic microorganisms and elucidating the mechanism of action.

Isolation and selection of autochthonous strains of Trichoderma spp. with inhibitory activity against Sporisorium reilianum

Head smut is a worldwide disease caused by the fungus Sporisorium reilianum. In Mexico, this phytosanitary problem has been described in the central part of the country, specifically in the Mezquital Valley in the state of Hidalgo, where this basidiomycete causes significant economic losses. In this work, seven strains of Trichoderma spp. were isolated from corn rhizospheres collected from crops in the affected zone. The isolates were identified as Trichoderma asperellum MH1, T. asperellum T4H1, T. harzianum T1H1, T. harzianum T1H3, T. atrobrunneum T1H2, T. tomentosum T2H4, and T. brevicompactum T3H1. All strains showed the ability to grow on the phytopathogen but with distinct degrees of mycoparasitism. SEM observations demonstrated the ability of T. asperellum T4H1 to invade the S. reilianum yeast growth. All the strains produced volatile compounds with antifungal activity. With the exception of T. asperellum MH1, all strains inhibited the development of the pathogen by means of non-volatile compounds. Production of the extracellular enzymes (lipase, cellulase, chitinase, protease, and laccase) was evaluated, with most strains presenting high lipolytic activity and low proteolytic activity. The production of cellulase and chitinase was observed only in five strains. Laccase production was found in three isolates. Evaluations at the greenhouse of the sequential application of three mixtures of the isolates were conducted in a greenhouse; findings showed that the phytopathogen was not detected by specific PCR in the plants that received the treatment.

Chitinase is a Potent Insecticidal Molecular Target of Camptothecin and Its Derivatives

Camptothecin (CPT) is a prominent molecule in natural product research because of its application prospects in medicine and agriculture. In this study, CPT and its derivatives were discovered to be competitive inhibitors of group II and group h insect chitinases, both of which are key components of insect chitinolytic systems. CPT and 7-ethyl-10-hydroxycamptothecin (SN-38) inhibited group II chitinase from Ostrinia furnacalis (OfChtII) with K_i values of 5.1 and 2.0 μM, respectively. Results from tryptophan fluorescence spectroscopy, molecular docking analysis, and molecular dynamics simulations revealed that both CPT and SN-38 inhibit OfChtII-C1 by interacting with solvent-exposed tryptophan residues in a substrate-binding cleft. CPT exhibited high insecticidal activity toward the orthopteran pest Locusta migratoria, possibly because of the midgut metabolism of CPT, with only moderate activities toward lepidopteran pests. Even though SN-38 exhibited much lower insecticidal activities than CPT, it still showed higher inhibitory activity toward chitinase. This study reports a new molecular target of CPT and provides insights into molecular design of CPT-based insecticides against different kinds of pests.

Thermo-neutrophilic cellulases and chitinases characterized from a novel putative antifungal biocontrol agent: Bacillus subtilis TD11

Cellulose and chitin are the most abundant naturally occurring biopolymers synthesized in plants and animals and are used for synthesis of different organic compounds and acids in the industry. Therefore, cellulases and chitinases are important for their multiple uses in industry and biotechnology. Moreover, chitinases have a role in the biological control of phytopathogens. A bacterial strain Bacillus subtilis TD11 was previously isolated and characterized as a putative biocontrol agent owing to its significant antifungal potential. In this study, cellulase and chitinase produced by the strain B. subtilis TD11 were purified and characterized. The activity of the cellulases and chitinases were optimized at different pH (2 to 10) and temperatures (20 to 90°C). The substrate specificity of cellulases was evaluated using different substances including carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), and crystalline substrates. The cellulase produced by B. subtilis TD11 had a molecular mass of 45 kDa while that of chitinase was 55 kDa. The optimal activities of the enzymes were found at neutral pH (6.0 to 7.0). The optimum temperature for the purified cellulases was in the range of 50 to 70°C while, purified chitinases were optimally active at 50°C. The highest substrate specificity of the purified cellulase was found for CMC (100%) followed by HEC (>50% activity) while no hydrolysis was observed against the crystalline substrates. Moreover, it was observed that the purified chitinase was inhibitory against the fungi containing chitin in their hyphal walls i.e., Rhizoctonia, Colletotrichum, Aspergillus and Fusarium having a dose-effect relationship.

An eco-friendly approach of biocontrol of aphid (Aphis gossypii Glover) by Trichoderma harzianum

Aphid (Aphis gossypii) is one of the important pests of papaya crop. In this work, applications of Trichoderma harzianum and Beauveria bassiana (biocontrol agents) and malathion (insecticide) were conducted in vitro and in agrifields for testing their anti-aphid efficacy and compared their efficacy. Furthermore, the enzymatic mechanism of T. harzianum with respect to biocontrolling the pest was unearthed. The LD₅₀ dose of T. harzianum and B. bassiana was 1.2 × 10⁵ spores mL^-1 and 1.0 × 10⁶ spores mL^-1 respectively after 48 h of administration. The LT₅₀ of T. harzianum also exhibited a lower effective time (47.70 h) than B. bassiana (57.53 h) for the same concentration of spores applied (1 × 10⁵ spores mL^-1). The pooled data analysis of two years (2019-2020) showed that the application of T. harzianum spores in agrifields exhibited 31.75 ± 13.00a percentage of reduction of aphid population whereas malathion exhibited 23.93 ± 1.30a%, in comparison to control. The statistical analysis indicated that the application of malathion exhibited the same efficacy as T. harzianum isolate and placed in the same category. In plate detection assay, T. harzianum produced a higher hydrolytic zone for chitinase (8.0 ± 0.4 cm diameter) and protease (7.0 ± 0.4 cm diameter) enzymes, than B. bassiana (1.3 ± 0.2 cm and 1.1 ± 0.2 cm respectively). Quantitative estimation of enzymes exhibited that T. harzianum produced 299 ± 11a μg mL^-1 of chitinase, 519 ± 19a μg mL^-1 of protease, and 65 ± 12a μg mL^-1 of PR1, and on the other hand, B. bassiana yielded 124 ± 12b, 361 ± 23b, and 29 ± 18b μg mL^-1 of chitinase, protease, and PR1 respectively. It indicated that T. harzianum was superior over the B. bassiana in terms of production capacity of all three enzymes. In conclusion, all the above experimental results suggested that T. harzianum showed better aphid-killing efficacy than B. bassiana. It also suggested that T. harzianum should replace hazardous chemical pesticide (malathion) for eco-friendly biocontrol of aphids.

Biological Characteristics of Recombinant Arthrobotrys oligospora Chitinase AO-801

Chitinase AO-801 is a hydrolase secreted by Arthrobotrys oligospora during nematode feeding, while its role remained elusive. This study analyzed the molecular characteristics of recombinant chitinase of Arthrobotrys oligospora (reAO-801). AO-801 belongs to the typical glycoside hydrolase 18 family with conserved chitinase sequence and tertiary structure of (α/β)8 triose-phosphate isomerase (TIM) barrel. The molecular weight of reAO-801 was 42 kDa. reAO-801 effectively degraded colloidal and powdered chitin, egg lysate, and stage I larval lysate of Caenorhabditis elegans. The activity of reAO-801 reached its peak at 40˚C and pH values between 4-7. Enzyme activity was inhibited by Zn2+, Ca2+, and Fe3+, whereas Mg2+ and K+ potentiated its activity. In addition, urea, sodium dodecyl sulfate, and 2-mercaptoethanol significantly inhibited enzyme activity. reAO-801 showed complete nematicidal activity against C. elegans stage I larvae. reAO-801 broke down the C. elegans egg shells, causing them to die or die prematurely by hatching the eggs. It also invoked degradation of Haemonchus contortus eggs, resulting in apparent changes in the morphological structure. This study demonstrated the cytotoxic effect of reAO-801, which laid the foundation for further dissecting the mechanism of nematode infestation by A. oligospora.

Efficacy of Entomopathogenic Fungal Formulations against Elasmolomus pallens (Dallas) (Hemiptera: Rhyparochromidae) and Their Extracellular Enzymatic Activities

Elasmolomus pallens are post-harvest insect pests of peanuts that are becoming resistant to chemical insecticides. In this, we study evaluated the effect of conidial formulations on entomopathogenic fungi against E. pallens to reduce the adverse effects. Fungal conidia were formulated and applied on sterile filter papers at varying concentrations (1 × 10⁴–1 × 10⁸ conidia mL⁻¹) inside plastic containers. The test insects were exposed and maintained in a relative humidity of 80 ± 10% for 10 d at room temperature (25 ± 2 °C). Mortality was recorded every 24 h. Dose–response bioassay (LC50 and LC90) values for Aspergillus flavus formulated in oil were 1.95 × 10⁶ and 3.66 × 10⁹ conidia/mL, whereas formulations in Tween 80 had 9.36 × 10⁷ and 6.50 × 10⁹ conidia/mL. However, oil-formulated Metarhizium anisopliae had 3.92 × 10⁶ and 2.57 × 10⁸ conidia/mL, with 6.85 × 10⁶ and 5.37 × 10⁸, for formulations in Tween 80. A. flavus had LT50 values of 3.3 and 6.6 days, whereas M. anisopliae had LT50 values of 3.6 and 5.7 d. Maximum protease, chitinase, and lipase activities of 2.51, 0.98, and 3.22 U/mL, respectively, were recorded for A. flavus, whereas values of 2.43, 0.93, and 3.46 were recorded for M. anisopliae. The investigated pathogens demonstrate potential against E. pallens; therefore, their applicability under field conditions requires further investigation.

A Broad-Specificity Chitinase from Penicillium oxalicum k10 Exhibits Antifungal Activity and Biodegradation Properties of Chitin

Penicillium oxalicum k10 isolated from soil revealed the hydrolyzing ability of shrimp chitin and antifungal activity against Sclerotinia sclerotiorum. The k10 chitinase was produced from a powder chitin-containing medium and purified by ammonium sulfate precipitation and column chromatography. The purified chitinase showed maximal activity toward colloidal chitin at pH 5 and 40 °C. The enzymatic activity was enhanced by potassium and zinc, and it was inhibited by silver, iron, and copper. The chitinase could convert colloidal chitin to N-acetylglucosamine (GlcNAc), (GlcNAc)2, and (GlcNAc)3, showing that this enzyme had endocleavage and exocleavage activities. In addition, the chitinase prevented the mycelial growth of the phytopathogenic fungi S. sclerotiorum and Mucor circinelloides. These results indicate that k10 is a potential candidate for producing chitinase that could be useful for generating chitooligosaccharides from chitinous waste and functions as a fungicide.

Maize Endochitinase Expression in Response to Fall Armyworm Herbivory

A large percentage of crop loss is due to insect damage, especially caterpillar damage. Plant chitinases are considered excellent candidates to combat these insects since they can degrade chitin in peritrophic matrix (PM), an important protective structure in caterpillar midgut. Compared to chemical insecticides, chitinases could improve host plant resistance and be both economically and environmentally advantageous. The focus of this research was to find chitinase candidates that could improve plant resistance by effectively limiting caterpillar damage. Five classes of endochitinase (I-V) genes were characterized in the maize genome, and we isolated and cloned four chitinase genes (chitinase A, chitinase B, chitinase I, and PRm3) present in two maize (Zea mays L.) inbred lines Mp708 and Tx601, with different levels of resistance to caterpillar pests. We also investigated the expression of these maize chitinases in response to fall armyworm (Spodoptera frugiperda, FAW) attack. The results indicated that both chitinase transcript abundance and enzymatic activity increased in response to FAW feeding and mechanical wounding. Furthermore, chitinases retained activity inside the caterpillar midgut and enzymatic activity was detected in the food bolus and frass. When examined under scanning electron microscopy, PMs from Tx601-fed caterpillars showed structural damage when compared to diet controls. Analysis of chitinase transcript abundance after caterpillar feeding and proteomic analysis of maize leaf trichomes in the two inbreds implicated chitinase PRm3 found in Tx601 as a potential insecticidal protein.

Deletions of the Idh1, Eco1, Rom2, and Taf10 Genes Differently Control the Hyphal Growth, Drug Tolerance, and Virulence of Candida albicans

The most recent genome-editing system called CRISPR-Cas9 (clustered regularly interspaced short palindromic repeat system with associated protein 9-nuclease) was employed to delete four non-essential genes (i.e., Caeco1, Caidh1, Carom2, and Cataf10) individually to establish their gene functionality annotations in pathogen Candida albicans. The biological roles of these genes were investigated with respect to the cell wall integrity and biogenesis, calcium/calcineurin pathways, susceptibility of mutants towards temperature, drugs and salts. All the mutants showed increased vulnerability compared to the wild-type background strain towards the cell wall-perturbing agents, (antifungal) drugs and salts. All the mutants also exhibited repressed and defective hyphal growth and smaller colony size than control CA14. The cell cycle of all the mutants decreased enormously except for those with Carom2 deletion. The budding index and budding size also increased for all mutants with altered bud shape. The disposition of the mutants towards cell wall-perturbing enzymes disclosed lower survival and more rapid cell wall lysis events than in wild types. The pathogenicity and virulence of the mutants was checked by adhesion assay, and strains lacking rom2 and eco1 were found to possess the least adhesion capacity, which is synonymous to their decreased pathogenicity and virulence.

A Cold-Adapted Chitinase-Producing Bacterium from Antarctica and Its Potential in Biocontrol of Plant Pathogenic Fungi

To obtain chitinase-producing microorganisms with high chitinolytic activity at low temperature, samples collected from Fildes Peninsula in Antarctica were used as sources for bioprospecting of chitinolytic microorganisms. A cold-adapted strain, designated as GWSMS-1, was isolated from marine sediment and further characterized as Pseudomonas. To improve the chitinase production, one-factor-at-a-time and orthogonal test approaches were adopted to optimize the medium components and culture conditions. The results showed that the highest chitinolytic activity (6.36 times higher than that before optimization) was obtained with 95.41 U L^-1 with 15 g L^-1 of glucose, 1 g L^-1 of peptone, 15 g L^-1 of colloid chitin and 0.25 g L^-1 of magnesium ions contained in the medium, cultivated under pH 7.0 and a temperature of 20 °C. To better understand the application potential of this strain, the enzymatic properties and the antifungal activity of the crude chitinase secreted by the strain were further investigated. The crude enzyme showed the maximum catalytic activity at 35 °C and pH 4.5, and it also exhibited excellent low-temperature activity, which still displayed more than 50% of its maximal activity at 0 °C. Furthermore, the crude chitinase showed significant inhibition of fungi Verticillium dahlia CICC 2534 and Fusarium oxysporum f. sp. cucumerinum CICC 2532, which can cause cotton wilt and cucumber blight, respectively, suggesting that strain GWSMS-1 could be a competitive candidate for biological control in agriculture, especially at low temperature.

Expression of Drosera rotundifolia Chitinase in Transgenic Tobacco Plants Enhanced Their Antifungal Potential

In this study, a chitinase gene (DrChit) that plays a role in the carnivorous processes of Drosera rotundifolia L. was isolated from genomic DNA, linked to a double CaMV35S promoter and nos terminator in a pBinPlus plant binary vector, and used for Agrobacterium-mediated transformation of tobacco. RT-qPCR revealed that within 14 transgenic lines analysed in detail, 57% had DrChit transcript abundance comparable to or lower than level of a reference actin gene transcript. In contrast, the transgenic lines 9 and 14 exhibited 72 and 152 times higher expression level than actin. The protein extracts of these two lines exhibited five and eight times higher chitinolytic activity than non-transgenic controls when measured in a fluorimetric assay with FITC-chitin. Finally, the growth of Trichoderma viride was obviously suppressed when the pathogen was exposed to 100 μg of crude protein extract isolated from line 9 and line 14, with the area of mycelium growth reaching only 56.4% and 45.2%, of non-transgenic control, respectively. This is the first time a chitinase from a carnivorous plant with substrate specificity for long chitin polymers was tested in a transgenic plant with the aim of exploring its antifungal potential.

A potent chitin-hydrolyzing enzyme from Myrothecium verrucaria affects growth and development of Helicoverpa armigera and plant fungal pathogens

Chitin, a crucial structural and functional component of insects and fungi, serves as a target for pest management by utilizing novel chitinases. Here, we report the biocontrol potential of recombinant Myrothecium verrucaria endochitinase (rMvEChi) against insect pest and fungal pathogens. A complete ORF of MvEChi (1185 bp) was cloned and heterologously expressed in Escherichia coli. Structure based sequence alignment of MvEChi revealed the presence of conserved domains SXGG and DXXDXDXE specific for GH-18 family, involved in substrate binding and catalysis, respectively. rMvEChi (46.6 kDa) showed optimum pH and temperature as 7.0 and 30 °C, respectively. Furthermore, rMvEChi remained stable within the pH range of 6.0 to 8.0 and up to 40 °C. rMvEChi exhibited k_cat/K_m values of 129.83 × 10³ [(g/L)^-1 s^-1] towards 4MU chitotrioside. Hydrolysis of chitooligosaccharides with various degrees of polymerization (DP) using rMvEChi indicated the release of DP2 as main end product with order of reaction as DP6 > DP5 > DP4 > DP3. Bioassay of rMvEChi against Helicoverpa armigera displayed potent anti-feedant activity and induced mortality. In vitro antifungal activity against plant pathogenic fungi (Ustilago maydis and Bipolaris sorokiniana) exhibited significant inhibition of mycelium growth. These results suggest that MvEChi has significant potential in enzyme-based pest and pathogen management.

Proteomic identification and purification of seed proteins from native Amazonian species displaying antifungal activity

Seeds of native species from the rain forest (Amazon) are source of chitinases and their protein extracts exhibited strong and broad antifungal activity. Numerous plant species native to the Amazon have not yet been chemically studied. Studies of seeds are scarcer, since adversities in accessing study areas and seasonality pose constant hurdles to systematic research. In this study, proteins were extracted from seeds belonging to endemic Amazon species and were investigated for the first time. Proteolytic activity, peptidase inhibitors, and chitinases were identified, but chitinolytic activity predominated. Four proteins were purified through chromatography and identified as lectin and chitinases by MS/MS analyses. The proteins were examined for inhibition of a phytopathogen (Fusarium oxysporum). Analyses by fluorescence microscopy suggested binding of propidium iodide to DNA of fungal spores, revealing that spore integrity was lost when accessed by the proteins. Further structural and functional analyses of defensive proteins belonging to species facing highly complex ecosystems such as Amazonia should be conducted, since these could provide new insights into specificity and synergism involving defense proteins of plants submitted to a very complex ecosystem.

Soybean seed coat chitinase as a defense protein against the stored product pest Callosobruchus maculatus

BACKGROUND

Chitinases (EC 3.2.1.14) are enzymes involved in the breaking of the β-1,4-glycosidic linkages of chitin. In insects, chitin is present mainly in the cuticle and in peritrophic membranes and peritrophic gel. Enzymes with the potential to damage peritrophic membranes and gel, such as chitinase, have been associated with plant defense systems. Identification and characterization of seed coat chitinase as a plant defense molecule may indicate a more effective target for manipulation strategies, which may lead to the prevention of consumption of embryonic tissues by larvae and consequently minimization of seed damage.

RESULTS

We studied the efficiency of soybean seed coat chitinase as a defense molecule against the insect Callosobruchus maculatus. The seed coat chitinase was isolated and identified by mass spectrometry, immunoreacted with an anti-chitinase antibody and shown to have activity against chitin azure and 4-methylumbelliferyl β-D-N,N',N''-triacetylchitotrioside. A chitinase fraction incorporated in artificial cotyledons at 0.1% reduced larval survival by approximately 77%, and at 0.5%, the reduction in larval mass was 60%. Fluorescein isothiocyanate (FITC)-labeled chitinase was detected in the guts and feces of larvae. At 25% in thick artificial seed coats, chitinase showed a high toxicity to larvae, with mortality of 90% and a reduction of larval mass of 87%.

CONCLUSION

Seed coat chitinase is an important seed defense molecule not only in the cotyledons but also in seed coats, acting as part of the array of defense mechanisms against Callosobruchus maculatus. © 2017 Society of Chemical Industry.

Improved antifungal activity of barley derived chitinase I gene that overexpress a 32kDa recombinant chitinase in Escherichia coli host

Agricultural crops suffer many diseases, including fungal and bacterial infections, causing significant yield losses. The identification and characterisation of pathogenesis-related protein genes, such as chitinases, can lead to reduction in pathogen growth, thereby increasing tolerance against fungal pathogens. In the present study, the chitinase I gene was isolated from the genomic DNA of Barley (Hordeum vulgare L.) cultivar, Haider-93. The isolated DNA was used as template for the amplification of the ∼935bp full-length chitinase I gene. Based on the sequence of the amplified gene fragment, class I barley chitinase shares 93% amino acid sequence homology with class II wheat chitinase. Interestingly, barley class I chitinase and class II chitinase do not share sequence homology. Furthermore, the amplified fragment was expressed in Escherichia coli Rosetta strain under the control of T7 promoter in pET 30a vector. Recombinant chitinase protein of 35kDa exhibited highest expression at 0.5mM concentration of IPTG. Expressed recombinant protein of 35kDa was purified to homogeneity with affinity chromatography. Following purification, a Western blot assay for recombinant chitinase protein measuring 35kDa was developed with His-tag specific antibodies. The purified recombinant chitinase protein was demonstrated to inhibit significantly the important phytopathogenic fungi Alternaria solani, Fusarium spp, Rhizoctonia solani and Verticillium dahliae compared to the control at concentrations of 80μg and 200μg.

Display of B. pumilus chitinase on the surface of B. subtilis spore as a potential biopesticide

BACKGROUND

Chitinases can inhibit the growth of many fungal diseases which are a great threat for global agricultural production. Biological control of pathogens like fungi, is believed to be one of the best ways to eliminate the adverse effects of plant pathogens. To this end, we expressed and displayed a chitinase from Bacillus pumilus (ChiS) on the surface of Bacillus subtilis spores, as a biocontrol agent.

RESULT

ChiS enzyme from B. pumilus was expressed on the spores of B. subtilis using CotG as a carrier protein. Immunofluorescence microscopy confirmed the expression of ChiS on the surface of the spores. Enzyme activity assay showed that the surface displayed ChiS was active and was also able to inhibit the growth of Rhizoctonia solani and Trichoderma harzianum fungi. Western blot analysis also indicated that CotG-ChiS is partially processed after display. Molecular dynamics simulation showed that the stability of the heterologous protein was decreased after fusion.

CONCLUSION

ChiS was successfully displayed on the surface of Bacillus spores by fusion to the CotG, one of the main spore coat proteins. In-vitro experiments showed that the displayed enzyme was effective in growth inhibition of R. solani and T. harzianum fungi.

Biocontrol potential of Halotolerant bacterial chitinase from high yielding novel Bacillus Pumilus MCB-7 autochthonous to mangrove ecosystem

The multifaceted role of chitinase in medicine, agriculture, environmental remediation and various other industries greatly demands the isolation of high yielding chitinase producing microorganisms with improved properties. The current study aimed to investigate the isolation, characterization and biocontrol prospective of chitinase producing bacterial strains autochthonous to the extreme conditions of mangrove ecosystems. Among the 51 bacterial isolates screened, Bacillus pumilus MCB-7 with highest chitinase production potential was identified and confirmed by 16S rDNA typing. Chitinase enzyme of MCB-7 was purified; the chitin degradation was evaluated by SEM and LC-MS. Unlike previously reported B.pumilus isolates, MCB-7 exhibited highest chitinase activity of 3.36U/mL, active even at high salt concentrations and temperature up to 60°C. The crude as well as purified enzyme showed significant antimycotic activity against agricultural pathogens such as Aspergillus flavus, Aspergillus niger, Aspergillus fumigatus, Ceratorhiza hydrophila and Fusarium oxysporum. The enzyme also exhibited biopesticidal role against larvae of Scirpophaga incertulas (Walker). [Lep.: Pyralidae], a serious agricultural pest of rice. The high chitinolytic and antimycotic potential of MCB-7 increases the prospects of the isolate as an excellent biocontrol agent. To the best of our knowledge, this is the first report of high chitinase yielding Bacillus pumilus strain from mangrove ecosystem with a biocontrol role against phytopathogenic fungi and insect larval pests.

Cladosporium cladosporioides and Cladosporium pseudocladosporioides as potential new fungal antagonists of Puccinia horiana Henn., the causal agent of chrysanthemum white rust

Puccinia horiana Hennings, the causal agent of chrysanthemum white rust, is a worldwide quarantine organism and one of the most important fungal pathogens of Chrysanthemum × morifolium cultivars, which are used for cut flowers and as potted plants in commercial production regions of the world. It was previously reported to be controlled by Lecanicillium lecanii, Cladosporium sphaerospermum, C. uredinicola and Aphanocladium album, due to their antagonistic and hyperparasitic effects. We report novel antagonist species on Puccinia horiana. Fungi isolated from rust pustules in a commercial greenhouse from Villa Guerrero, México, were identified as Cladosporium cladosporioides and Cladosporium pseudocladosporioides based upon molecular analysis and morphological characters. The antagonism of C. cladosporioides and C. pseudocladosporioides on chrysanthemum white rust was studied using light and electron microscopy in vitro at the host/parasite interface. Cladosporium cladosporioides and C. pseudocladosporioides grew towards the white rust teliospores and colonized the sporogenous cells, but no direct penetration of teliospores was observed; however, the structure and cytoplasm of teliospores were altered. The two Cladosporium spp. were able to grow on media containing laminarin, but not when chitin was used as the sole carbon source; these results suggest that they are able to produce glucanases. Results from the study indicate that both Cladosporium species had potential as biological control agents of chrysanthemum white rust.

Improvement of chitinase Pachi with nematicidal activities by random mutagenesis

Chitinase, an enzyme that can degrade the main compositions of insect intestine and cuticle, has been used in the bio-control field. Our previous work has reported the chitinase Pachi with nematicidal activity (Caenorhabditis elegans). In the present study, to improve the chitinolytic and nematicidal activities of Pachi, a random mutant library was constructed by error-prone PCR and screened by bacteriophage T7-based high-throughput screening system. One mutant, Pachi_N35D was obtained from about 10, 000 clones. The kinetics analysis revealed that Pachi_N35D exhibited a 63% decrease in K_m value against chitosan, a 2.1-fold enhancement in k_cat/K_m value and a 1.2-fold increase in specific activity over the wild-type Pachi. Moreover, the mortality analysis against Caenorhabditis elegans showed that the 50% lethal concentration (LC₅₀) of Pachi_N35D is 309.6±1.1μg/ml and a 20% increase in nematicidal activity over the wild-type Pachi (with a LC₅₀ value of 387.3±31.7μg/ml). The structure modeling and superimposition indicated that the substitution N35D reduced the distance between substrate and substrate-binding site Asp141, finally resulting in an increase in substrate affinity, catalytic efficiency and specific activity. These results provide useful information for the study of structure-function relationship of Pachi and lay a foundation for its potential applications in agro-biotechnology.

First insights into the diversity and functional properties of chitinases of the latex of Calotropis procera

Chitinases (EC 3.2.1.14) found in the latex of Calotropis procera (Ait) R. Br. were studied. The proteins were homogeneously obtained after two ion exchange chromatography steps. Most proteins were identified individually in 15 spots on 2-D gel electrophoresis with isoelectric points ranging from 4.6 to 6.0 and molecular masses extending from 27 to 30 kDa. Additionally, 66 kDa proteins were identified as chitinases in SDS-PAGE. Their identities were further confirmed by mass spectrometry (MS) analysis of the tryptic digests of each spot and MS analysis of the non-digested proteins. Positive reaction for Schiff's reagent suggested the proteins are glycosylated. The chitinases exhibited high catalytic activity toward to colloidal chitin at pH 5.0, and this activity underwent decay in the presence of increasing amounts of reducing agent dithiothreitol. Spore germination and hyphae growth of two phytopathogenic fungi were inhibited only marginally by the chitinases but were affected differently. This suggested a complex relationship might exist between the specificity of the proteins toward the fungal species. The chitinases showed potent insecticidal activity against the Bruchidae Callosobruchus maculatus, drastically reducing survival, larval weight and adult emergence. It is concluded that closely related chitinases are present in the latex of C. procera, and the first experimental evidence suggests these proteins are involved more efficiently in defence strategies against insects rather than fungi.

Antifungal potential of actinomycete isolate Streptomyces exfoliates MT9 against wood-rotting fungi

An actinomycete isolate, Streptomyces exfoliatus MT9 was assessed for in vitro antagonism against wood-rotting fungi. Strain MT9 showed strong antagonistic activity (ZOI ? 25 mm) towards various tested wood-rotting fungi. Extracellular production of antifungal metabolite(s) including primary and secondary was monitored up to 10 days of submerged fermentation. Antagonist S. exfoliatus MT9 produces fungal cell-wall lytic enzymes, namely chitinase (3.098 U ml-1), b-1,3 glucanase (2.4 U ml-1) and protease (144.0 U ml-1) and also showed antifungal activity towards tested P. chrysosporium MTCC 787 (12.0 mm) and P. placenta MTCC 144 (16.0 mm). Extracellular culture filtrate (ECF) of S. exfoliatus MT9 also exhibited strong antifungal activity (ZOI ≥ 25 mm) towards tested wood-rotting fungi and n-butanol was found to be the suitable solvent for complete extraction of antifungal metabolite(s) from ECF. Reduced antifungal activity of n-butanol extract against P. chrysosporium MTCC 787 (11.00 mm) and P. placenta MTCC 144 (10.00 mm) on ergosterol agar plate, no activity against bacteria and characteristic UV spectra at 224 nm revealed the polyene nature of antifungal metabolite(s) present in the n-butanol extract. A novel actinomycete isolate, S. exfoliatus MT9 is producing antifungal metabolite(s) that makes it suitable for biotechnological processes and has the potential to be used as a bioactive agent for controlling wood-rotting fungi.

Effects of Trichoderma viride chitinases on the peritrophic matrix of Lepidoptera

BACKGROUND

The peritrophic matrix (PM) is formed by a network of chitin fibrils associated with proteins, glycoproteins and proteoglycans that lines the insect midgut. It is a physical barrier involved in digestion processes, and protects the midgut epithelium from food abrasion, pathogen infections and toxic materials. Given its fundamental role in insect physiology, the PM represents an excellent target for pest control strategies. Although a number of viral, bacterial and insect chitinolytic enzymes affecting PM integrity have already been tested, exploitation of fungal chitinases has been almost neglected. Fungal chitinases, already in use as fungal phytopathogen biocontrol agents, are known to attack the insect cuticle, but their action on the insect gut needs to be better investigated.

RESULTS

In the present paper, we performed a biochemical characterisation of a commercial mixture of chitinolytic enzymes derived from Trichoderma viride and analysed its in vitro and in vivo effects on the PM of the silkworm Bombyx mori, a model system among Lepidoptera. We found that these enzymes have significant in vitro effects on the structure and permeability of the PM of this insect. A bioassay supported these results and showed that the oral administration of the mixture causes PM alterations, leading to adverse consequences on larval growth and development, negatively affecting pupal weight and even inducing mortality.

CONCLUSIONS

This study provides an integrated experimental approach to evaluate the effects of fungal chitinases on Lepidoptera. The encouraging results obtained herein make us confident about the possible use of fungal chitinases to control lepidopteran pests.

Enhanced nematicidal potential of the chitinase pachi from Pseudomonas aeruginosa in association with Cry21Aa

Nematodes are known to be harmful to various crops, vegetables, plants and insects. The present study reports that, chitin upregulates the activity of chitinase (20%) and nematicidal potential (15%) of Pseudomonas aeruginosa. The chitinase gene (pachi) from P. aeruginosa was cloned, and its nematicidal activity of pachi protein against Caenorhabditis elegans was studied. The mortality rate induced by pachi increased by 6.3-fold when in association with Cry21Aa from Bacillus thuringiensis. Pachi efficiently killed C. elegans in its native state (LC50 = 387.3 ± 31.7 μg/ml), as well as in association with Cry21Aa (LC50 = 30.9 ± 4.1 μg/ml), by degrading the cuticle, egg shell and intestine in a relatively short time period of 24 h. To explore the nematidal potential of chitinase, six fusion proteins were constructed using gene engineering techniques. The CHACry showed higher activity against C. elegans than others owing to its high solubility. Notably, the CHACry showed a synergistic factor of 4.1 versus 3.5 a mixture [1:1] of pachi and Cry21Aa. The present study has identified eco-friendly biological routes (e.g., mixed proteins, fusion proteins) with potent nematicidal activity, which not only can help to prevent major crop losses but also strengthen the agro-economy and increase gross crop yield.

Significance of Penicillium ochrochloron chitinase as a biocontrol agent against pest Helicoverpa armigera

Penicillium ochrochloron chitinase purified by DEAE-cellulose ion exchange chromatography was evaluated for its antifeedant and growth inhibitory activities against Helicoverpa armigera at different concentrations of 2000, 1000, 500, 250 and 100 U mL(-1). It reduced the successful pupation and increased larval and pupal mortality, adult emergence in a dosage-dependent manner when applied topically. The highest mortalities were recorded for groups treated with 2000 U mL(-1) chitinase activity. The studies showed P.ochrochloron chitinase can affect the growth of H.armigera larvae. Since this insect pest species has developed resistance and resurgence to chemical insecticides, only alternate is the usage of enzyme-based pesticide formulations as an environmentally friendly pest management tool.

Anti-fungal potentials of extracellular metabolites of Western Ghats isolated Streptomyces sp. NII 1006 against moulds and yeasts

Realization of hazardious effects of chemical fungicides has led to an interest in the usage of biocontrol agents. The present study, therefore, evaluates the biocontrol efficacy of Western Ghats (India) soil bacterial isolates. A potential strain NII 1006 was evaluated for its antagonistic property against a diverse range of moulds and yeasts. The strain was characterized morphologically, biochemically and molecularly, which revealed the isolate belonged to Streptomyces genus. Organic solvent extracts of NII 1006 culture filtrates inhibited the growth of the test pathogens indicating that growth suppression was due to extracellular anti-fungal metabolites present in the culture filtrates. The strain produced extracellular chitinase enzyme in addition to some stable partially purified anti-fungal compounds. Morphological changes such as hyphae degradation into debris and abnormal shapes were observed in test fungi and yeast grown on potato dextrose broth that contained the NII 1006 culture filtrate. The cell free supernatant has a tolerance to wide range of pH, temperature and enzymes such as lipase and protease. The biocontrol potential of NII 1006 strain may be correlated significantly with their ability to produce antibiotics as well as extracellular hydrolytic enzymes particularly chitinolytic enzyme.

Comparison of Enzymatic and Antifungal Properties between Family 18 and 19 Chitinases fromS. coelicolorA3(2)

Streptomyces coelicolor A3(2) has 13 chitinase genes encoding 11 family 18 and two family 19 chitinases. To compare enzymatic properties of family 19 chitinase and family 18 chitinases produced by the same organism, the four chitinases (Chi18bA, Chi18aC, Chi18aD, and Chi19F), whose genes are expressed at high levels in the presence of chitin, were produced in Escherichia coli and purified. The effect of pH on the hydrolytic activity was very different not only among the four chitinases but also among the substrates. The hydrolytic activity of Chi19F, family 19 chitinase, against soluble substrates was remarkably high as compared with three family 18 chitinases, but was the lowest against crystalline substrates among the four chitinases. On the contrary, Chi18aC, a family 18-subfamily A chitinase, showed highest activity against crystalline substrates. Only Chi19F exhibited significant antifungal activity. Based on these observations, the roles of family 19 chitinases are discussed.

Effect ofBombyx moriChitinase against Japanese Pine Sawyer (Monochamus alternatus) Adults as a Biopesticide

Bombyx mori chitinase (Bm-CHI), with a molecular mass of 75 kDa, was investigated on the possibility that it can serve as a biocontrol agent against the adult Japanese pine sawyer (JPS), Monochamus alternatus (Coleoptera: Cerambycidae). Oral ingestion of purified chitinase at concentrations of 3 microM (11.25 microg/50 microl) and 0.3 micoM (1.125 microg/50 microl) caused high mortality in JPS, a significant decrease in bark consumption, and, only in high concentration, a slight reduction of body weight. Fluorescence assays indicated that peritrophic membrane (PM) chitin is degraded by the action of orally ingested Bm-CHI at 3 microM concentration only. Scanning electron micrographs clearly indicated that the beetles that ingested Bm-CHI of the same high concentration had their PM perforated and disrupted, but ultrastructural studies showed that the ingested chitinase did not affect the midgut epithelium. These findings open up the possibility of using insect chitinase as a biopesticidal enzyme. It should have agronomic potential for insect control.

Purification, Characterization, and Antifungal Activity of Chitinases from Pineapple (Ananas comosus) Leaf

Three chitinases, designated pineapple leaf chitinase (PL Chi)-A, -B, and -C were purified from the leaves of pineapple (Ananas comosus) using chitin affinity column chromatography followed by several column chromatographies. PL Chi-A is a class III chitinase having a molecular mass of 25 kDa and an isoelectric point of 4.4. PL Chi-B and -C are class I chitinases having molecular masses of 33 kDa and 39 kDa and isoelectric points of 7.9 and 4.6 respectively. PL Chi-C is a glycoprotein and the others are simple proteins. The optimum pHs of PL Chi-A, -B, and -C toward glycolchitin are pH 3, 4, and 9 respectively. The chitin-binding ability of PL Chi-C is higher than that of PL Chi-B, and PL Chi-A has lower chitin-binding ability than the others. At low ionic strength, PL Chi-B exhibits strong antifungal activity toward Trichoderma viride but the others do not. At high ionic strength, PL Chi-B and -C exhibit strong and weak antifungal activity respectively. PL Chi-A does not have antifungal activity.

Antifungal chitinase against human pathogenic yeasts from Coprinellus congregatus

The inky cap, Coprinellus congregatus, produces mushrooms which become autolyzed rapidly to generate black liquid droplets, in which no cell wall is detected by microscopy. A chitinase (Chi2) which is synthesized during the autolytic phase of C. congregatus inhibits the growths of Candida albicans and Cryptococcus neoformans up to 10% at the concentration of 10 μg/ml, about 50% at concentration of 20 μg/ml, and up to 95% at the concentration of 70 μg/ml. Upon treatment these yeast cells are observed to be severely deformed, with the formation of large holes in the cell wall. The two yeast species show no growth inhibition at the concentration of 5 μg/ml, which means the minimum inhibitory concentrations for both yeast species are 10 μg/ml under these experimental conditions.

Both extracellular chitinase and a new cyclic lipopeptide, chromobactomycin, contribute to the biocontrol activity of Chromobacterium sp. C61

Chromobacterium sp. strain C61 displays antifungal activities in vitro and has been used successfully for the biocontrol of plant diseases under field conditions. In this study, the roles of extracellular chitinase and an antifungal compound produced by strain C61 were investigated to elucidate their contributions to biological control activity. The bacterium possessed a locus chi54 encoding an extracellular chitinase, and mutation of chi54 eliminated chitinase production. Production of the extracellular enzyme and expression of the chi54 transcript were increased in the wild-type strain when chitin was added to the culture medium. In vitro assays showed that purified chitinase inhibited spore germination of multiple pathogens. However, the in planta biocontrol activity of filtrates of cultures grown in the presence of chitin was lower than that of filtrates grown without chitin, indicating that correlation between chitinase and biocontrol activity was lacking. The analysis of C61 culture filtrates revealed an antifungal cyclic lipopeptide, chromobactomycin, whose structure contained a unique nonameric peptide ring. The purified chromobactomycin inhibited the growth of several phytopathogenic fungi in vitro, and plant application significantly reduced disease severity for several pathogens. Furthermore, the production of chromobactomycin was reduced in cultures amended with chitin. These data suggest that the production of both the extracellular chitinase Chi54 and the newly identified antibiotic chromobactomycin can contribute, in an interconnected way, to the suppression of plant disease by Chromobacterium sp. strain C61.

Anti-fungi activities of Bacillus thuringiensis H3 chitinase and immobilized chitinase particles and their effects to rice seedling defensive enzymes

The chitinase producing bacterium H3 strain was screened from nature with the selective medium and was identified as Bacillus thuringiensis. The purpose of this investigation is to study the antifungi activity of Bacillus thuringiensis H3 chitinase and its immobilized particles, and the effects on growth of rice seedlings and activities of defensive enzymes. The rice seedlings qualities and several defense enzymes activity were measured after rice seedlings were treated by free chitinase and immobilized chitinase particles. The results show that the height and dry weight of the rice considerably increased in comparison with the control. Bacillus thuringiensis H3 chitinase and it's immobilized particles significantly inhibit several pathogenic fungi, and the anti-fungi rates of immobilized chitinase particles on Pyricularia grisea, Thantephorus cucumris, Fusarium vasinfectum, Fusarium gramineum, Fusarium oxysporum are 72.2%, 62.6%, 44.6%, 50.0%, 55.8%, respectively. Phenylalanine ammonia-lyase (PAL) and peroxidase (POD) activities of the rice seedling were significantly increased when it was treated by free chitinase and immobilized chitinase particles. From the results it could be concluded that Bacillus thuringiensis H3 free chitinase and immobilized chitinase particles can inhibit several pathogenic fungi and induce rice seedlings defense enzymes activity changes.

Combined expression of antimicrobial genes (Bbchit1 and LJAMP2) in transgenic poplar enhances resistance to fungal pathogens

Populus species are susceptible to infection by microbial pathogens that severely affect their growth and substantially decrease their economic value. In this study, two pathogenesis-related protein genes consisting of Beauveria bassiana chitinase (Bbchit1) and motherwort lipid-transfer protein (LJAMP2) were introduced into Chinese white poplar (Populus tomentosa Carr.) via Agrobacterium-mediated transformation using the hygromycin (hyg) and neomycin phosphotransferase (NPTII) genes as selectable markers, respectively. Polymerase chain reaction analysis confirmed the stable integration of transgenes in the genome of transgenic plants. In vitro assays showed that inhibitory activity against the fungal pathogen Alternaria alternata (Fr.) Keissler was evident from the crude leaf extracts from transgenic plants. Importantly, the double-transgenic plants exhibited significantly higher resistance to the pathogen than either of the single-gene transformants and wild-type plants when inoculated with A. alternata. The level of disease reduction in double-transgenic lines was between 82 and 95%, whereas that of single-gene transformants carrying either LJAMP2 or Bbchit1 was between 65 and 89%. These results indicated that the combined expression of the LJAMP2 and Bbchit-1 genes could significantly enhance resistance to necrotrophic fungal pathogens in poplar.

Identification of an E-box motif responsible for the expression of jasmonic acid-induced chitinase gene OsChia4a in rice

The plant hormone jasmonic acid (JA) is known to be involved in multiple defence responses against pathogens, which include the production of pathogenesis-related (PR) proteins. In order to investigate the induction mechanism of the rice defence responses by JA, we performed transcriptome analyses and focused on a chitinase gene, OsChia4a, which was identified to be one of the highest JA-inductive genes. The recombinant protein of His-tagged OsChia4a exhibited an inhibitory effect against the spore germination and hyphal growth of Magnaporthe oryzae. The promoter analysis of OsChia4a revealed that the region from -515 bp to -265 bp upstream of the ATG translation initiation site was required for the responsiveness to JA. A subsequent mutation analysis indicated that an E-box (CANNTG) in this region act as a JA-responsive cis element. These results imply that a basic helix-loop-helix transcription factor is likely to be involved in the regulation of the OsChia4a expression in a JA-dependent manner.

Effect of chitinase on resistance to fungal pathogens in sea buckthorn, Hippophae rhamnoides, and cloning of Class I and III chitinase genes

Sea buckthorn (Hippophae rhamnoides L.) is naturally distributed from Asia to Europe. It has been widely planted as an ornamental shrub and is rich in nutritional and medicinal compounds. Fungal pathogens that cause diseases such as dried-shrink disease are threats to the production of this plant. In this study, we isolated the dried-shrink disease pathogen from bark and total chitinase protein from leaves of infected plants. The results of the Oxford Cup experiment suggested that chitinase protein inhibited the growth of this pathogen. To improve pathogen resistance, we cloned chitinase Class I and III genes in H. rhamnoides, designated Hrchi1 and Hrchi3. The full-length cDNA of the open reading frame region of Hrchi1 contained 903 bp encoding 300 amino acids and Hrchi3 contained 894 bp encoding 297 amino acids. Active domain analysis, protein types, and secondary and 3D structures were predicted using online software.

A Chitinase from Aeromonas veronii CD3 with the potential to control myxozoan disease

Background

The class Myxosporea encompasses about 2,400 species, most of which are parasites of fish and cause serious damage in aquaculture. Due to the concerns about food safety issues and limited knowledge of Myxozoa life cycle and fish immune system, no chemicals, antibiotics or immune modulators are available to control myxozoa infection. Therefore, little can be done once Myxozoa establishment has occurred.

Methodology/Principal Findings

In this paper we isolated Aeromonas veronii CD3 with significant myxospore shell valve-degrading ability from pond sediment. A 3,057-bp full-length chitinase gene was consequently cloned, and the corresponding mature, recombinant chitinase (ChiCD3) produced by Escherichia coli had substantial chitinase activity. The deduced sequence of ChiCD3 contained one catalytic domain, two chitin-binding domains, and one putative signal peptide. ChiCD3 had an optimal activity at 50°C and pH 6.0, and retained more than 50% of its optimal activity under warm water aquaculture conditions (∼30°C and pH ∼7.0). After incubation with ChiCD3, 38.0±4.8% of the myxospores had damaged shell valves, whereas myxospores incubated with commercially available chitinases remained intact.

Conclusion/Significance

This study reveals a new strategy to control myxozoan disease. ChiCD3 that has capacity to damage the shell valve of myxospores can be supplemented into fish feed and used to control Myxozoa-induced diseases specifically.

Potential fungal inhibition by immobilized hydrolytic enzymes from Trichoderma asperellum

The use of cell wall degrading enzymes from Trichoderma asperellum immobilized on biodegradable support is an alternative for food packaging. In this study, hydrolytic enzymes produced by T. asperellum were tested as a fungal growth inhibitor, in free form or immobilized on a biodegradable film composed of cassava starch and poly(butylene adipate-co-terephtalate) (PBAT). The inhibitory activity was tested against Aspergillus niger , Penicillium sp., and Sclerotinia sclerotiorum , microorganisms that frequently degrade food packaging. The use of chitin as carbon source in liquid medium induced T. asperellun to produce N-acetylglucosaminidase, β-1,3-glucanase, chitinase, and protease. The presence of T. asperellun cell wall degradating enzymes (T-CWD) immobilized by adsorption or covalent attachment resulted in effective inhibition of fungal growth. The enzymatic activity of T-CWD was stronger on S. sclerotiorum than on the Aspergillus or Penicillum isolates tested. These results suggest that T-CWD can be used in a free or immobilized form to suppress fungi that degrade food packaging.

A new chitinase-like xylanase inhibitor protein (XIP) from coffee (Coffea arabica) affects Soybean Asian rust (Phakopsora pachyrhizi) spore germination

BACKGROUND

Asian rust (Phakopsora pachyrhizi) is a common disease in Brazilian soybean fields and it is difficult to control. To identify a biochemical candidate with potential to combat this disease, a new chitinase-like xylanase inhibitor protein (XIP) from coffee (Coffea arabica) (CaclXIP) leaves was cloned into the pGAPZα-B vector for expression in Pichia pastoris.

RESULTS

A cDNA encoding a chitinase-like xylanase inhibitor protein (XIP) from coffee (Coffea arabica) (CaclXIP), was isolated from leaves. The amino acid sequence predicts a (β/α)8 topology common to Class III Chitinases (glycoside hydrolase family 18 proteins; GH18), and shares similarity with other GH18 members, although it lacks the glutamic acid residue essential for catalysis, which is replaced by glutamine. CaclXIP was expressed as a recombinant protein in Pichia pastoris. Enzymatic assay showed that purified recombinant CaclXIP had only residual chitinolytic activity. However, it inhibited xylanases from Acrophialophora nainiana by approx. 60% when present at 12:1 (w/w) enzyme:inhibitor ratio. Additionally, CaclXIP at 1.5 μg/μL inhibited the germination of spores of Phakopsora pachyrhizi by 45%.

CONCLUSIONS

Our data suggests that CaclXIP belongs to a class of naturally inactive chitinases that have evolved to act in plant cell defence as xylanase inhibitors. Its role on inhibiting germination of fungal spores makes it an eligible candidate gene for the control of Asian rust.

The effect of chitin metabolic effectors on the population increase of stored product mites

The study tested the effect of the chitin metabolic effectors, teflubenzuron, diflubenzuron, and calcofluor, and a combination of a chitinase and soybean trypsin inhibitor (STI) on the population growth of eight species of stored product mites under laboratory conditions. The compounds were incorporated into the diets of the mites in concentrations ranging from 0.01 to 50 mg g(-1). The final populations of mites were observed after 21 days of growth in controlled conditions. Diflubenzuron and calcofluor suppressed the growth of all the tested species more effectively than the other compounds. The doses required to suppress the mite populations to 50% (rc(50)) in comparison to the control ranged from 0.29 to 12.68 mg g(-1) for diflubenzuron and from 1.75 to 37.7 mg g(-1) for calcofluor, depending on the mite species. When tested at the highest concentration (10 mg g(-1)), teflubenzuron also suppressed all of the tested mite species in comparison to the control. The addition of chitinase/STI into the diet influenced population growth in several ways. When the highest concentration of chitinase in a cocktail of chitinase and STI (12.5 mg g(-1) of diet) was compared to the control, populations of Acarus siro, Aleuroglyphus ovatus and Aëroglyphus robustus decreased significantly, whereas populations of Tyroborus lini and Sancassania rodionovi increased significantly. The sensitivity of species to the tested compounds differed among species. The most tolerant species was S. rodionovi, the most sensitive was A. ovatus. The results confirmed that calcofluor and diflubenzuron have a toxic effect on stored product mites.

A viral chitinase enhances oral activity of TMOF

In this study we investigate the combined effect on Heliothis virescens (Lepidoptera, Noctuidae) larvae of Aedes aegypti-Trypsin Modulating Oostatic Factor (Aea-TMOF), a peptide that inhibits trypsin synthesis by the gut, impairing insect digestive function, and Autographa californica nucleopolyhedrovirus Chitinase A (AcMNPV ChiA), an enzyme that is able to alter the permeability of the peritrophic membrane (PM). Aea-TMOF and AcMNPV ChiA were provided to the larvae by administering transgenic tobacco plants, co-expressing both molecules. Experimental larvae feeding on these plants, compared to those alimented on plants expressing only one of the two molecules considered, showed significantly stronger negative effects on growth rate, developmental time and mortality. The impact of AcMNPV ChiA on the PM of H. virescens larvae, measured as increased permeability to molecules, was evident after five days of feeding on transgenic plants expressing ChiA. This result was confirmed by in vitro treatment of PM with recombinant ChiA, extracted from the transgenic plants used for the feeding experiments. Collectively, these data indicate the occurrence of a positive interaction between the two transgenes concurrently expressed in the same plant. The hydrolytic activity of ChiA on the PM of tobacco budworm larvae enhances the permeation of TMOF molecules to the ectoperitrophic space, and its subsequent absorption. The permeation through the paracellular route of Aea-TMOF resulted in a spotted accumulation on the basolateral domain of enterocytes, which suggests the occurrence of a receptor on the gut side facing the haemocoel. The binding of the peptide, permeating at increased rates due to the ChiA activity, is considered responsible for the enhanced insecticide activity of the transgenic plants expressing both molecules. These data corroborate the idea that ChiA can be effectively used as gut permeation enhancer in oral delivery strategies of bioinsecticides targeting haemocoelic receptors.

Differential expression of maize chitinases in the presence or absence of Trichoderma harzianum strain T22 and indications of a novel exo- endo-heterodimeric chitinase activity

BACKGROUND

The interaction of plants with endophytic symbiotic fungi in the genus Trichoderma alters the plant proteome and transcriptome and results in enhanced plant growth and resistance to diseases. In a previous study, we identified the numerous chitinolytic enzyme families and individual enzymes in maize which are implicated in plant disease resistance and other plant responses.

RESULTS

We examined the differential expression of the entire suite of chitinolytic enzymes in maize plants in the presence and absence of T. harzianum. Expression of these enzymes revealed a band of chitinolytic enzyme activity that had greater mass than any known chitinase. This study reports the characterization of this large protein. It was found to be a heretofore undiscovered heterodimer between an exo- and an endo-enzyme, and the endo portion differed between plants colonized with T. harzianum and those grown in its absence and between shoots and roots. The heterodimeric enzymes from shoots in the presence and absence of T. harzianum were purified and characterized. The dimeric enzyme from Trichoderma-inoculated plants had higher specific activity and greater ability to inhibit fungal growth than those from control plants. The activity of specific chitinolytic enzymes was higher in plants grown from Trichoderma treated seeds than in control plants.

CONCLUSIONS

This is the first report of a dimer between endo- and exochitinase. The endochitinase component of the dimer changed post Trichoderma inoculation. The dimer originating from Trichoderma inoculated plants had a higher antifungal activity than the comparable enzyme from control plants.

Purification and characterization of a viral chitinase active against plant pathogens and herbivores from transgenic tobacco

The Autographa californica nucleopolyhedrovirus chitinase A (AcMNPV ChiA) is a chitinolytic enzyme with fungicidal and insecticidal properties. Its expression in transgenic plants enhances resistance against pests and fungal pathogens. We exploited tobacco for the production of a biologically active recombinant AcMNPV ChiA (rChiA), as such species is an alternative to traditional biological systems for large-scale enzyme production. The protein was purified from leaves using ammonium sulfate precipitation followed by anion exchange and gel-filtration chromatography. Transgenic plants produced an estimated 14 mg kg(-1) fresh leaf weight, which represents 0.2% of total soluble proteins. The yield of the purification was about 14% (2 mg kg(-1) fresh leaf weight). The comparison between the biochemical and kinetic properties of the rChiA with those of a commercial Serratia marcescens chitinase A indicated that the rChiA was thermostable and more resistant at basic pH, two positive features for agricultural and industrial applications. Finally, we showed that the purified rChiA enhanced the permeability of the peritrophic membrane of larvae of two Lepidoptera (Bombyx mori and Heliothis virescens) and inhibited spore germination and growth of the phytopatogenic fungus Alternaria alternata. The data indicated that tobacco represents a suitable platform for the production of rChiA, an enzyme with interesting features for future applications as "eco-friendly" control agent in agriculture.

Characterization of an antifungal and cryoprotective class I chitinase from table grape berries (Vitis vinifera cv. Cardinal)

Gene expression of a class I chitinase (Vcchit1b) in the skin of table grapes was analyzed as a molecular marker for changes induced at low temperature and also to study the effect of high CO(2) levels modulating transcript levels at 0 degrees C. An active recombinant VcCHIT1b was overexpressed in Escherichia coli, and as the protein was produced as insoluble inclusion bodies, it was solubilized and refolded. The purified recombinant chitinase showed an optimum pH of 6.0 and a temperature of 50 degrees C, retaining activity at 0 and -10 degrees C. Purified chitinase exerted in vitro antifungal activity against Botrytis cinerea. Furthermore, recombinant chitinase was able to cryoprotect lactate dehydrogenase against freeze/thaw inactivation. However, the recombinant VcCHIT1b did not show any antifreeze activity when the thermal hysteresis activity was measured using differential scanning calorimetry.

Analysis of the involvement of chitin-binding domain of ChiCW in antifungal activity, and engineering a novel chimeric chitinase with high enzyme and antifungal activities

An antifungal chitinase, ChiCW, produced by Bacillus cereus 28-9 is effective against conidial germination of Botrytis elliptica, the causal agent of lily leaf blight. ChiCW as a modular enzyme consists of a signal peptide, a catalytic domain, a fibronectin type-III-like domain, and a chitin-binding domain. When two C-terminal domains of ChiCW were truncated, ChiCWdeltaFC (lacking the chitin-binding domain and fibronectin type III-like domain) lost its antifungal activity. Since ChiCWdeltaAC (lacking the chitin-binding domain) could not be expressed in Escherichia coli as ChiCWdeltaFC did, a different strategy based on protein engineering technology was designed to investigate the involvement of the chitin-binding domain of ChiCW (ChBD(ChiCW)) in antifungal activity in this study. Because ChiA1 of Bacillus circulans WL-12 is a modular enzyme with a higher hydrolytic activity than ChiCW but not inhibitory to conidial germination of Bo. elliptica and the similar domain composition of ChiA1 and ChiCW, the C-terminal truncated derivatives of ChiA1 were generated and used to construct chimeric chitinases with ChBD(ChiCW). When the chitin-binding domain of ChiA1 was replaced with ChBD(ChiCW), the chimeric chitinase named ChiAAAW exhibited both high enzyme activity and antifungal activity. The results indicate that ChBD(ChiCW) may play an important role in the antifungual activity of ChiCW.

A family 19 chitinase (Chit30) from Streptomyces olivaceoviridis ATCC 11238 expressed in transgenic pea affects the development of T. harzianum in vitro

Embryo axes excised from mature seeds of pea (Pisum sativum L.) cv. 'Sponsor' were used as explants for Agrobacterium-mediated transformation using pGreenII 0229 binary vectors. The vectors harbored a chimeric chitinase gene (chit30), driven by the constitutive 35S promoter or the elicitor inducible stilbene synthase (vst) promoter from grape (Vitis vinifera L.). The secretion signal of the bacterial chitinase gene from Streptomyces olivaceoviridis ATCC 11238 (DSM 41433) was replaced by the A. thaliana basic chitinase leader sequence. Functional properties of the recombinant gene were tested in tobacco as a model system before the long process of pea transformation was undertaken. Several transgenic pea clones were obtained and the transgenic nature confirmed by different molecular methods. The accumulation and activity of chitinase in stably transformed plants were examined by Western blot analysis and in-gel assays, which showed the presence of an additional 3 isoform bands. Using in vitro bioassays with Trichoderma harzanium as a model, we found an inhibition or delay of hyphal extension, which might indicate enhanced antifungal activity compared with non-transformed pea plants. Up to the 4th generation, the transgenic plants did not show any phenotypic alterations compared with non-transgenic control plants.

Strategies to improve the insecticidal activity of Cry toxins from Bacillus thuringiensis

Bacillus thuringiensis Cry toxins have been widely used in the control of insect pests either as spray products or expressed in transgenic crops. These proteins are pore-forming toxins with a complex mechanism of action that involves the sequential interaction with several toxin-receptors. Cry toxins are specific against susceptible larvae and although they are often highly effective, some insect pests are not affected by them or show low susceptibility. In addition, the development of resistance threatens their effectiveness, so strategies to cope with all these problems are necessary. In this review we will discuss and compare the different strategies that have been used to improve insecticidal activity of Cry toxins. The activity of Cry toxins can be enhanced by using additional proteins in the bioassay like serine protease inhibitors, chitinases, Cyt toxins, or a fragment of cadherin receptor containing a toxin-binding site. On the other hand, different modifications performed in the toxin gene such as site-directed mutagenesis, introduction of cleavage sites in specific regions of the protein, and deletion of small fragments from the amino-terminal region lead to improved toxicity or overcome resistance, representing interesting alternatives for insect pest control.

Cloning and expression of an antifungal chitinase gene of a novel Bacillus subtilis isolate from Taiwan potato field

A chitinase producing Bacillus subtilis CHU26 was isolated from Taiwan potato field. This strain exhibited a strong extra-cellular chitinase activity on the colloidal chitin containing agar plate, and showed a potential inhibit activity against phytopathogen, Rhizoctonia solani. The gene encoding chitinase (chi18) was cloned from the constructed B. subtilis CHU26 genomic DNA library. The chi18 consisted of an open reading frame of 1791 nucleotides and encodes 595 amino acids with a deduced molecular weight of 64kDa, next to a promoter region containing a 9 base pair direct repeat sequence (ATTGATGAA). The deduced amino acid sequence of the chitinase from Bacillus subtilis CHU26 exhibits 62% and 81% similarity to those from B. circulans WL-12 and B. licheniformis, respectively. Subcloned chi18 into vector pGEM3Z and pYEP352 to construct recombinant plasmid pGCHI18 and pYCHI18, respectively, chitinase activity could be observed on the colloidal chitin agar plate from recombinant plasmid containing Escherichia coli transformant. Cell-free culture broth of pYCHI18 containing E. coli transformant decreased R. solani pathogenic activity more than 90% in the antagonistic test on the radish seedlings (Raphanus sativus Linn.).