Chitin Deacetylase from Bacillus aryabhattai TCI-16: Heterologous Expression, Characterization, and Deacetylation Performance

Chitin deacetylase (CDA) removes the acetyl group from the chitin molecule to generate chitosan in a uniform, high-quality deacetylation pattern. Herein, BaCDA was a novel CDA discovered from our previously isolated Bacillus aryabhattai strain TCI-16, which was excavated from mangrove soil. The gene BaCDA was cloned and overexpressed in Escherichia coli BL21 (DE3) to facilitate its subsequent purification. The purified recombinant protein BaCDA was obtained at a concentration of about 1.2 mg/mL after Ni2+ affinity chromatography. The molecular weight of BaCDA was around 28 kDa according to the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. In addition, BaCDA exhibited a significant deacetylation effect on colloidal chitin, and the deacetylation degree was measured from the initial 25.69 to 69.23% by Fourier transform infrared (FT-IR) spectroscopy. Scanning electron microscopy (SEM) observation showed that the surface of colloidal chitin after enzymatic digestion was rough, the crystal fibers disappeared, and the chitin structure was loose and porous with grooves. The results of electrospray ionization mass spectrometry (ESI-MS) showed that BaCDA had full-deacetylation activity against (GlcNAc)4. Molecular docking revealed that BaCDA had an open active pocket capable of binding to the GlcNAc unit. This study not only provides a novel enzymatic resource for the green and efficient application of chitin but also helps to deepen the understanding of the catalytic mechanism of CDA.

Cloning and Characterization of Chitin Deacetylase from Euphausia superba

Chitin deacetylase (CDA) can catalyze the deacetylation of chitin to produce chitosan. In this study, we identified and characterized a chitin deacetylase gene from Euphausia superba (EsCDA-9k), and a soluble recombinant protein chitin deacetylase from Euphausia superba of molecular weight 45 kDa was cloned, expressed, and purified. The full-length cDNA sequence of EsCDA-9k was 1068 bp long and encoded 355 amino acid residues that contained the typical domain structure of carbohydrate esterase family 4. The predicted three-dimensional structure of EsCDA-9k showed a 67.32% homology with Penaeus monodon. Recombinant chitin deacetylase had the highest activity at 40 °C and pH 8.0 in Tris-HCl buffer. The enzyme activity was enhanced by metal ions Co2+, Fe3+, Ca2+, and Na+, while it was inhibited by Zn2+, Ba2+, Mg2+, and EDTA. Molecular simulation of EsCDA-9k was conducted based on sequence alignment and homology modeling. The EsCDA-9k F18G mutant showed a 1.6-fold higher activity than the wild-type enzyme. In summary, this is the first report of the cloning and heterologous expression of the chitin deacetylase gene in Euphausia superba. The characterization and function study of EsCDA-9k will serve as an important reference point for future application.

Rational Design of a Potential New Nematicide Targeting Chitin Deacetylase

In a previously published study, the authors devised a molecular topology QSAR (quantitative structure-activity relationship) approach to detect novel fungicides acting as inhibitors of chitin deacetylase (CDA). Several of the chosen compounds exhibited noteworthy activity. Due to the close relationship between chitin-related proteins present in fungi and other chitin-containing plant-parasitic species, the authors decided to test these molecules against nematodes, based on their negative impact on agriculture. From an overall of 20 fungal CDA inhibitors, six showed to be active against Caenorhabditis elegans. These experimental results made it possible to develop two new molecular topology-based QSAR algorithms for the rational design of potential nematicides with CDA inhibitor activity for crop protection. Linear discriminant analysis was employed to create the two algorithms, one for identifying the chemo-mathematical pattern of commercial nematicides and the other for identifying nematicides with activity on CDA. After creating and validating the QSAR models, the authors screened several natural and synthetic compound databases, searching for alternatives to current nematicides. Finally one compound, the N2-(dimethylsulfamoyl)-N-{2-[(2-methyl-2-propanyl)sulfanyl]ethyl}-N2-phenylglycinamide or nematode chitin deacetylase inhibitor, was selected as the best candidate and was further investigated both in silico, through molecular docking and molecular dynamic simulations, and in vitro, through specific experimental assays. The molecule shows favorable binding behavior on the catalytic pocket of C. elegans CDA and the experimental assays confirm potential nematicide activity.

tritici confers disease pathogenicity by suppressing chitin-triggered immunity in wheat

Plants have the ability to recognize the essential chitin molecule present in the fungal cell wall, which stimulates the immune response. Phytopathogenic fungi have developed various strategies to inhibit the chitin-triggered immune response. Here, we identified a chitin deacetylase of Puccinia striiformis f. sp. tritici (Pst), known as PsCDA2, that was induced during the initial invasion of wheat and acted as an inhibitor of plant cell death. Knockdown of PsCDA2 in wheat enhanced its resistance against Pst, highlighting the significance of PsCDA2 in the host-pathogen interaction. Moreover, PsCDA2 can protect Pst urediniospores from being damaged by host chitinase in vitro. PsCDA2 also suppressed the basal chitin-induced plant immune response, including the accumulation of callose and the expression of defence genes. Overall, our results demonstrate that Pst secretes PsCDA2 as a chitin deacetylase involved in establishing infection and modifying the acetyl group to prevent the breakdown of chitin in the cell wall by host endogenous chitinases. Our research unveils a mechanism by which the fungus suppresses plant immunity, further contributing to the understanding of wheat stripe rust control. This information could have significant implications for the development of suitable strategies for protecting crops against the devastating effects of this disease.

A comprehensive immunoinformatic analysis of chitin deacetylase's and MP88 for designing multi-epitope vaccines against Cryptococcus neoformans

Cryptococcus neoformans causes life-threatening pneumonia and meningitis and is regarded as one of the leading killers of immunocompromised individuals. There is currently no vaccine against this pathogen. Recently, WHO placed it at the top among the critical priority groups in the fungal priority pathogens to accelerate the development of effective treatments. Numerous studies suggested the potential of subunit vaccines to overcome the challenges associated with live and inactivated whole-cell vaccines. Therefore, this study exploited integrated reverse vaccinology and immunoinformatic approach to construct and characterize multi-epitope vaccines targeting chitin deacetylases (Cda1, Cda2, Cda3) and MP88 of C. neoformans. 4 CTL, 8 HTL and 6 B cell epitopes were fused with different adjuvants and appropriate linkers to design two multi-epitope vaccines (VC1 and VC2). Both chimeric constructs were predicted to be highly antigenic, non-allergenic, non-toxic, soluble and had satisfactory physicochemical properties. Molecular docking and binding free energy calculation revealed strong binding interactions between vaccine constructs and human TLRs (TLR-2 and TLR-4). Classical MD Simulation and Normal mode analysis verified the stability of the vaccine-TLR complex in the biological environment. Codon adaptation, cloning and in silico expression suggested the efficient expression of recombinant vaccine proteins in E. coli. Both candidates also generated robust immune profiles comprising innate, adaptive and humoral immune responses. Taken together, experimental validations of our findings through extensive in vitro and in vivo testing might provide an effective vaccine for prophylactic control of C. neoformans.Communicated by Ramaswamy H. Sarma.

Cell wall composition in Cryptococcus neoformans is media dependent and alters host response, inducing protective immunity

Introduction

Cryptococcus neoformans is a basidiomycete fungus that can cause meningoencephalitis, especially in immunocompromised patients. Cryptococcus grows in many different media, although little attention has been paid to the role of growth conditions on the cryptococcal cell wall or on virulence.

Objective

The purpose of this study was to determine how different media influenced the amount of chitin and chitosan in the cell wall, which in turn impacted the cell wall architecture and host response.

Methods

Yeast extract, peptone, and dextrose (YPD) and yeast nitrogen base (YNB) are two commonly used media for growing Cryptococcus before use in in vitro or in vivo experiments. As a result, C. neoformans was grown in either YPD or YNB, which were either left unbuffered or buffered to pH 7 with MOPS. These cells were then labeled with cell wall-specific fluorescent probes to determine the amounts of various cell wall components. In addition, these cells were employed in animal virulence studies using the murine inhalation model of infection.

Results

We observed that the growth of wild-type C. neoformans KN99 significantly changes the pH of unbuffered media during growth. It raises the pH to 8.0 when grown in unbuffered YPD but lowers the pH to 2.0 when grown in unbuffered YNB (YNB-U). Importantly, the composition of the cell wall was substantially impacted by growth in different media. Cells grown in YNB-U exhibited a 90% reduction in chitosan, the deacetylated form of chitin, compared with cells grown in YPD. The decrease in pH and chitosan in the YNB-U-grown cells was associated with a significant increase in some pathogen-associated molecular patterns on the surface of cells compared with cells grown in YPD or YNB, pH 7. This altered cell wall architecture resulted in a significant reduction in virulence when tested using a murine model of infection. Furthermore, when heat-killed cells were used as the inoculum, KN99 cells grown in YNB-U caused an aberrant hyper-inflammatory response in the lungs, resulting in rapid animal death. In contrast, heat-killed KN99 cells grown in YNB, pH 7, caused little to no inflammatory response in the host lung, but, when used as a vaccine, they conferred a robust protective response against a subsequent challenge infection with the virulent KN99 cells.

Conclusion

These findings emphasize the importance of culture media and pH during growth in shaping the content and organization of the C. neoformans cell wall, as well as their impact on fungal virulence and the host response.

Three Chitin Deacetylase Family Members of Beauveria bassiana Modulate Asexual Reproduction and Virulence of Fungi by Mediating Chitin Metabolism and Affect Fungal Parasitism and Saprophytic Life

As an important chitin-modifying enzyme, chitin deacetylase (CDA) has been characterized in many fungi, but its function in the entomopathogenic fungus Beauveria bassiana remains unclear. Three CDAs with conserved domains of the carbohydrate esterase 4 (CE-4) family were identified in B. bassiana. Disruption of CDA1 resulted in growth restriction of the fungus on medium with chitin as a carbon source or without a carbon source. Deletion of CDA1 and CDA2 led to defects in fungal conidial formation and conidial vitality compared with those of the wild type (WT), and the conidial yield decreased by 25.81% to 47.68%. Inactivation of three CDA genes resulted in a decrease of 20.23% to 27% in the blastospore yield. ΔCDA1 and ΔCDA3 showed 29.33% and 23.34% reductions in cuticular infection virulence, respectively. However, the CDA family may not contribute to hemocoel infection virulence. Additionally, the sporulation of the insect carcass showed that the three gene deletion mutants were 68.45%, 63.84%, and 56.65% less than WT. Penetration experiments with cicada wings and enzyme activity assays were used to further explore the effect of the fungus on chitin metabolism after gene deletion. Although the three gene deletion mutants penetrated the cicada wings successfully and continued to grow on the underlying medium, their colony sizes were reduced by 29.12% to 47.76%. The CDA enzyme activity of ΔCDA1 and ΔCDA3 decreased by 84.76% and 83.04%, respectively. These data showed that members of the CDA family play a different role in fungal growth, conidial quality, and virulence. IMPORTANCE In this study, we report the roles of CDA family in entomopathogenic fungus B. bassiana. Our results indicated that CDA modulates asexual development and regulates fungal virulence by altering chitin deacetylation and metabolic capacity. CDA affected the biological control potential and life history of B. bassiana by affecting its parasitic and saprophytic life. These findings provide novel insights into the roles of multiple CDA paralogues existing in fungal biocontrol agents.

Group V Chitin Deacetylases Influence the Structure and Composition of the Midgut of Beet Armyworm, Spodoptera exigua

Chitin deacetylase (CDA) can accelerate the conversion of chitin to chitosan, influencing the mechanical properties and permeability of the cuticle structures and the peritrophic membrane (PM) in insects. Putative Group V CDAs SeCDA6/7/8/9 (SeCDAs) were identified and characterized from beet armyworm Spodoptera exigua larvae. The cDNAs of SeCDAs contained open reading frames of 1164 bp, 1137 bp, 1158 bp and 1152 bp, respectively. The deduced protein sequences showed that SeCDAs are synthesized as preproteins of 387, 378, 385 and 383 amino acid residues, respectively. It was revealed via spatiotemporal expression analysis that SeCDAs were more abundant in the anterior region of the midgut. The SeCDAs were down-regulated after treatment with 20-hydroxyecdysone (20E). After treatment with a juvenile hormone analog (JHA), the expression of SeCDA6 and SeCDA8 was down-regulated; in contrast, the expression of SeCDA7 and SeCDA9 was up-regulated. After silencing SeCDAV (the conserved sequences of Group V CDAs) via RNA interference (RNAi), the layer of intestinal wall cells in the midgut became more compact and more evenly distributed. The vesicles in the midgut were small and more fragmented or disappeared after SeCDAs were silenced. Additionally, the PM structure was scarce, and the chitin microfilament structure was loose and chaotic. It was indicated in all of the above results that Group V CDAs are essential for the growth and structuring of the intestinal wall cell layer in the midgut of S. exigua. Additionally, the midgut tissue and the PM structure and composition were affected by Group V CDAs.

Combined Application of Tacrolimus with Cyproconazole, Hymexazol and Novel {2-(3-R-1H-1,2,4-triazol-5-yl)phenyl}amines as Antifungals: In Vitro Growth Inhibition and In Silico Molecular Docking Analysis to Fungal Chitin Deacetylase

Agents with antifungal activity play a vital role as therapeutics in health care, as do fungicides in agriculture. Effectiveness, toxicological profile, and eco-friendliness are among the properties used to select suitable substances. Furthermore, a steady supply of new agents with different modes of action is required to counter the well-known potential of human and phyto-pathogenic fungi to develop resistance against established antifungals. Here, we use an in vitro growth assay to investigate the activity of the calcineurin inhibitor tacrolimus in combination with the commercial fungicides cyproconazole and hymexazol, as well as with two earlier reported novel {2-(3-R-1H-1,2,4-triazol-5-yl)phenyl}amines, against the fungi Aspergillus niger, Colletotrichum higginsianum, Fusarium oxysporum and the oomycete Phytophthora infestans, which are notoriously harmful in agriculture. When tacrolimus was added in a concentration range from 0.25 to 25 mg/L to the tested antifungals (at a fixed concentration of 25 or 50 mg/L), the inhibitory activities were distinctly enhanced. Molecular docking calculations revealed triazole derivative 5, (2-(3-adamantan-1-yl)-1H-1,2,4-triazol-5-yl)-4-chloroaniline), as a potent inhibitor of chitin deacetylases (CDA) of Aspergillus nidulans and A. niger (AnCDA and AngCDA, respectively), which was stronger than the previously reported polyoxorin D, J075-4187, and chitotriose. The results are discussed in the context of potential synergism and molecular mode of action.

Isolation and screening of a chitin deacetylase producing Bacillus cereus and its potential for chitosan preparation

Chitosan is a biopolymer material extracted from marine biomass waste such as shrimp and crab shells, which has good biocompatibility and degradability with great potential for application in the field of wastewater treatment and soil remediation. The higher the degree of deacetylation (DD), the better the adsorption performance of chitosan. Chitin deacetylase (CDA) can specifically catalyze the deacetylate of chitin in a green reaction that is environmentally friendly. However, the scarcity of high yielding chitin deacetylase strains has been regarded as the technical bottleneck of chitosan green production. Here, we screened a natural chitin degrading bacterium from coastal mud and identified it as Bacillus cereus ZWT-08 by re-screening the chitin deacetylase activity and degree of deacetylation values. By optimizing the medium conditions and enzyme production process, ZWT-08 was cultured in fermentation medium with 1% (m/V) glucose and yeast extract at pH 6.0, 37°C, and a stirring speed of 180 r/min. After fermenting in 5 L fermenter for 48 h, the deacetylation activity of the supernatant reached 613.25 U/mL. Electron microscopic examination of the chitin substrate in the fermentation medium revealed a marshmallow-like fluffy texture on its structural surface. Meanwhile, 89.29% of the acetyl groups in this chitin substrate were removed by enzymatic digestion of chitin deacetylase produced by ZWT-08, resulting in the preparation of chitosan a degree of deacetylation higher than 90%. As an effective strain for chitosan production, Bacillus cereus ZWT-08 plays a positive role in the bioconversion of chitin and the upgrading of the chitosan industry.

Expression and Molecular Modification of Chitin Deacetylase from Streptomyces bacillaris

Chitin deacetylase can be used in the green and efficient preparation of chitosan from chitin. Herein, a novel chitin deacetylase SbCDA from Streptomyces bacillaris was heterologously expressed and comprehensively characterized. SbDNA exhibits its highest deacetylation activity at 35 °C and pH 8.0. The enzyme activity is enhanced by Mn²⁺ and prominently inhibited by Zn²⁺, SDS, and EDTA. SbCDA showed better deacetylation activity on colloidal chitin, (GlcNAc)₅, and (GlcNAc)₆ than other forms of the substrate. Molecular modification of SbCDA was conducted based on sequence alignment and homology modeling. A mutant SbCDA63G with higher activity and better temperature stability was obtained. The deacetylation activity of SbCDA63G was increased by 133% compared with the original enzyme, and the optimal reaction temperature increased from 35 to 40 °C. The half-life of SbCDA63G at 40 °C is 15 h, which was 5 h longer than that of the original enzyme. The improved characteristics of the chitin deacetylase SbCDA63G make it a potential candidate to industrially produce chitosan from chitin.

Genomic and transcriptomic analyses of chitin metabolism enzymes in Tenebrio molitor

Chitin is of great importance in the cuticle and inner cuticular linings of insects. Chitin synthases (CHSs), chitin deacetylases (CDAs), chitinases (CHTs), and β-N-acetylhexosaminidases (HEXs) are important enzymes required for chitin metabolism, and play essential roles in development and metamorphosis. Although chitin metabolism genes have been well characterized in limited insects, the information in the yellow mealworm, Tenebrio molitor, a model insect, is presently still unavailable. With the help of bioinformatics, we identified 54 genes that encode putative chitin metabolism enzymes, including 2 CHSs, 10 CDAs, 32 CHTs, and 10 HEXs in the genome of T. molitor. All these genes have the conserved domains and motifs of their corresponding protein family. Phylogenetic analyses indicated that CHS genes were divided into two groups. CDA genes were clustered into five groups. CHT genes were phylogenetically grouped into 11 clades, among which 1 in the endo-β-N-acetylglucosaminidases group and the others were classified in the glycoside hydrolase family 18 groups. HEX genes were assorted into six groups. Developmental and tissue-specific expression profiling indicated that the identified chitin metabolism genes showed dynamical expression patterns concurrent with specific instar during molting period, suggesting their significant roles in molting and development. They were predominantly expressed in different tissues or body parts, implying their functional specialization and diversity. The results provide important information for further clarifying their biological functions using the yellow mealworm as an ideal experimental insect.

A Novel Potent Crystalline Chitin Decomposer: Chitin Deacetylase from Acinetobacter schindleri MCDA01

Chitosan is a functional ingredient that is widely used in food chemistry as an emulsifier, flocculant, antioxidant, or preservative. Chitin deacetylases (CDAs) can catalyze the hydrolysis of acetyl groups, making them useful in the clean production of chitosan. However, the high inactivity of crystalline chitin catalyzed by CDAs has been regarded as the technical bottleneck of crystalline chitin deacetylation. Here, we mined the AsCDA gene from the genome of Acinetobacter schindleri MCDA01 and identified a member of the uraD_N-term-dom superfamily, which was a novel chitin deacetylase with the highest deacetylation activity. The AsCDA gene was expressed in Escherichia coli BL21 by IPTG induction, whose activity to colloidal chitin, α-chitin, and β-chitin reached 478.96 U/mg, 397.07 U/mg, and 133.27 U/mg, respectively. In 12 h, the enzymatic hydrolysis of AsCDA removed 63.05% of the acetyl groups from α-chitin to prepare industrial chitosan with a degree of deacetylation higher than 85%. AsCDA, as a potent chitin decomposer in the production of chitosan, plays a positive role in the upgrading of the chitosan industry and the value-added utilization of chitin biological resources.

Biodegradation and Prospect of Polysaccharide from Crustaceans

Marine crustacean waste has not been fully utilized and is a rich source of chitin. Enzymatic degradation has attracted the wide attention of researchers due to its unique biocatalytic ability to protect the environment. Chitosan (CTS) and its derivative chitosan oligosaccharides (COSs) with various biological activities can be obtained by the enzymatic degradation of chitin. Many studies have shown that chitosan and its derivatives, chitosan oligosaccharides (COSs), have beneficial properties, including lipid-lowering, anti-inflammatory and antitumor activities, and have important application value in the medical treatment field, the food industry and agriculture. In this review, we describe the classification, biochemical characteristics and catalytic mechanisms of the major degrading enzymes: chitinases, chitin deacetylases (CDAs) and chitosanases. We also introduced the technology for enzymatic design and modification and proposed the current problems and development trends of enzymatic degradation of chitin polysaccharides. The discussion on the characteristics and catalytic mechanism of chitosan-degrading enzymes will help to develop new types of hydrolases by various biotechnology methods and promote their application in chitosan.

tritici and increases the resistance to Bgt in wheat

The biotrophic fungal pathogen Blumeria graminis f. sp. tritici (Bgt) is a crucial factor causing reduction in global wheat production. Wild wheat relatives, for example Thinopyrum intermedium, is one of the wild-used parents in wheat disease-resistant breeding. From T. intermedium line, we identified the aspartic protease gene, TiAP1, which is involved in resistance against Bgt. TiAP1 is a secreted protein that accumulates in large amounts at the infection sites of Bgt and extends to the intercellular space. Yeast two-hybrid, luciferase complementation imaging and bimolecular florescent complimentary analysis showed that TiAP1 interacted with the chitin deacetylase (BgtCDA1) of Bgt. The yeast expression, purification and in vitro test confirmed the chitin deacetylase activity of BgtCDA1. The bombardment and VIGS-mediated host-induced gene silencing showed that BgtCDA1 promotes the invasion of Bgt. Transcriptome analysis showed the cell wall xylan metabolism, lignin biosynthesis-related and defence genes involved in the signal transduction were up-regulated in the transgenic TiAP1 wheat induced by Bgt. The TiAP1 in wheat may inactivate the deacetylation function of BgtCDA1, cause chitin oligomers expose to wheat chitin receptor, then trigger the wheat immune response to inhibit the growth and penetration of Bgt, and thereby enhance the resistance of wheat to pathogens.

Chitin Deacetylase, a Novel Target for the Design of Agricultural Fungicides

Fungicide resistance is a serious problem for agriculture. This is particularly apparent in the case of powdery mildew fungi. Therefore, there is an urgent need to develop new agrochemicals. Chitin is a well-known elicitor of plant immunity, and fungal pathogens have evolved strategies to overcome its detection. Among these strategies, chitin deacetylase (CDA) is responsible for modifying immunogenic chitooligomers and hydrolysing the acetamido group in the N-acetylglucosamine units to avoid recognition. In this work, we tested the hypothesis that CDA can be an appropriate target for antifungals using the cucurbit powdery mildew pathogen Podosphaera xanthii. According to our hypothesis, RNAi silencing of PxCDA resulted in a dramatic reduction in fungal growth that was linked to a rapid elicitation of chitin-triggered immunity. Similar results were obtained with treatments with carboxylic acids such as EDTA, a well-known CDA inhibitor. The disease-suppression activity of EDTA was not associated with its chelating activity since other chelating agents did not suppress disease. The binding of EDTA to CDA was confirmed by molecular docking studies. Furthermore, EDTA also suppressed green and grey mould-causing pathogens applied to oranges and strawberries, respectively. Our results conclusively show that CDA is a promising target for control of phytopathogenic fungi and that EDTA could be a starting point for fungicide design.

Polycistronic Expression System for Pichia pastoris Composed of Chitino- and Chitosanolytic Enzymes

Chitin is one of the most abundant biopolymers. Due to its recalcitrant nature and insolubility in accessible solvents, it is often considered waste and not a bioresource. The products of chitin modification such as chitosan and chitooligosaccharides are highly sought, but their preparation is a challenging process, typically performed with thermochemical methods that lack specificities and generate hazardous waste. Enzymatic treatment is a promising alternative to these methods, but the preparation of multiple biocatalysts is costly. In this manuscript, we biochemically characterised chitin deacetylases of Mucor circinelloides IBT-83 and utilised one of them for the construction of the first eukaryotic, polycistronic expression system employing self-processing 2A sequences. The three chitin-processing enzymes; chitin deacetylase of M. circinelloides IBT-83, chitinase from Thermomyces lanuginosus, and chitosanase from Aspergillus fumigatus were expressed under the control of the same promoter in methylotrophic yeast Pichia pastoris and characterised for their synergistic action towards their respective substrates.

Characterization and functional analysis of chitinase family genes involved in nymph-adult transition of Sogatella furcifera

Chitinase degrades chitin in the old epidermis or peritrophic matrix of insects, which ensures normal development and metamorphosis. In our previous work, we comprehensively studied the function of SfCht7 in Sogatella furcifera. However, the number and function of chitinase genes in S. furcifera remain unknown. Here, we identified 12 full-length chitinase transcripts from S. furcifera, which included nine chitinase (Cht), two imaginal disc growth factor (IDGF), and one endo-β-N-acetylglucosaminidase (ENGase) genes. Expression analysis results revealed that the expression levels of eight genes (SfCht3, SfCht5, SfCht6-1, SfCht6-2, SfCht7, SfCht8, SfCht10, and SfIDGF2) with similar transcript levels peaked prior to molting of each nymph and were highly expressed in the integument. Based on RNA interference (RNAi), description of the functions of each chitinase gene indicated that the silencing of SfCht5, SfCht10, and SfIDGF2 led to molting defects and lethality. RNAi inhibited the expressions of SfCht5, SfCht7, SfCht10, and SfIDGF2, which led to downregulated expressions of chitin synthase 1 (SfCHS1, SfCHS1a, and SfCHS1b) and four chitin deacetylase genes (SfCDA1, SfCDA2, SfCDA3, and SfCDA4), and caused a change in the expression level of two trehalase genes (TRE1 and TRE2). Furthermore, silencing of SfCht7 induced a significant decrease in the expression levels of three wing development-related genes (SfWG, SfDpp, and SfHh). In conclusion, SfCht5, SfCht7, SfCht10, and SfIDGF2 play vital roles in nymph-adult transition and are involved in the regulation of chitin metabolism, and SfCht7 is also involved in wing development; therefore, these genes are potential targets for control of S. furcifera.

Identification and RNAi-Based Functional Analysis of Four Chitin Deacetylase Genes in Sogatella furcifera (Hemiptera: Delphacidae)

Chitin deacetylases (CDAs) are chitin-degrading enzymes that play a key role in insect molting. In this study, we identified and characterized four full-length cDNAs of CDAs from Sogatella furcifera (Horváth). Developmental expression showed that SfCDA1 and SfCDA2 were expressed at all nymph developmental stages, SfCDA3 and SfCDA4 were mainly expressed in the third-instar to fifth-instar nymph stages, whereas tissue-specific analyses indicated that four CDA genes were mainly high expressed in the integument and head during the fifth-instar nymph. RNA interference (RNAi) results revealed that SfCDA1, SfCDA2, and SfCDA4 are associated with molting defect and high mortality with nymph-adult molting. Furthermore, transcripts of chitin synthase 1 variants (SfCHS1, SfCHS1a, and SfCHS1b) were significantly downregulated and causing significant changes in the expression levels of trehalases (TRE1 and TRE2) in the SfCDA1, SfCDA2, and SfCDA4 dsRNA treatment groups. By contrast, no significant phenotypic characteristics were observed after dsSfCDA3 injection. Taken together, our results suggest that SfCDA1, SfCDA2, and SfCDA4 play a vital role in nymph-adult transition, and these genes could regulate chitin biosynthesis expression levels.

A Conserved Machinery Underlies the Synthesis of a Chitosan Layer in the Candida Chlamydospore Cell Wall

The polysaccharide chitosan is found in the cell wall of specific cell types in a variety of fungal species where it contributes to stress resistance, or in pathogenic fungi, virulence. Under certain growth conditions, the pathogenic yeast Candida dubliniensis forms a cell type termed a chlamydospore, which has an additional internal layer in its cell wall compared to hyphal or yeast cell types. We report that this internal layer of the chlamydospore wall is rich in chitosan. The ascospore wall of Saccharomyces cerevisiae also has a distinct chitosan layer. As in S. cerevisiae, formation of the chitosan layer in the C. dubliniensis wall requires the chitin synthase CHS3 and the chitin deacetylase CDA2 In addition, three lipid droplet-localized proteins-Rrt8, Srt1, and Mum3-identified in S. cerevisiae as important for chitosan layer assembly in the ascospore wall are required for the formation of the chitosan layer of the chlamydospore wall in C. dubliniensis These results reveal that a conserved machinery is required for the synthesis of a distinct chitosan layer in the walls of these two yeasts and may be generally important for incorporation of chitosan into fungal walls.IMPORTANCE The cell wall is the interface between the fungal cell and its environment and disruption of cell wall assembly is an effective strategy for antifungal therapies. Therefore, a detailed understanding of how cell walls form is critical to identify potential drug targets and develop therapeutic strategies. This study shows that a set of genes required for the assembly of a chitosan layer in the cell wall of S. cerevisiae is also necessary for chitosan formation in a different cell type in a different yeast, C. dubliniensis Because chitosan incorporation into the cell wall can be important for virulence, the conservation of this pathway suggests possible new targets for antifungals aimed at disrupting cell wall function.

Screening and Identification of Sponge-Associated Chitinolytic Bacteria by Forming Chitosan from Manado Bay, Indonesia

BACKGROUND AND OBJECTIVE

Chitosan can be produced through the enzymatic process catalyzed by chitin deacetylase which can be produced by bacteria. The biotransformation of chitin to chitosan by bacteria is interesting because the process is economical and environmentally friendly. This study described the potential of sponge-associated bacterium capability in degrading chitin and forming chitosan.

MATERIALS AND METHODS

The bacteria were isolated from sponge Cribrochalina sp. at Manado Bay, Indonesia. In the screening of the chitinase activity of bacteria, chitin media was used. Meanwhile, the transformation of chitin to chitosan was tested by using Chitinase Degrading Activity media. Molecular identification of bacteria was based on 16S rRNA gene sequences.

RESULTS

The results showed that the SS1, SS2, SS3, SS4 and SS5 bacterial isolates could degrade chitin based on chitinolytic indexes. These five bacteria could also form chitosan exhibited through the presence of chitosan in the form of precipitation in the fermented broth of bacteria. SS1 had the highest chitinase activity based on the chitinolytic index identified as Bacillus subtilis (100% identity), hence it is called B. subtilis strain SS1. The partial rRNA gene sequences data were deposited at GenBank under accession number MN999892.

CONCLUSION

The bacteria strain isolated from Cribrochalina sp. can be utilized in degrading chitin and form chitosan which could be a promising candidate for an economical and eco-friendly process of chitosan.

Chitosan and Chitin Deacetylase Activity Are Necessary for Development and Virulence of Ustilago maydis

The basidiomycete Ustilago maydis causes smut disease in maize, causing substantial losses in world corn production. This nonobligate pathogen penetrates the plant cell wall with the help of appressoria and then establishes an extensive biotrophic interaction, where the hyphae are tightly encased by the plant plasma membrane.

The biotrophic fungus Ustilago maydis harbors a chitin deacetylase (CDA) family of six active genes as well as one pseudogene which are differentially expressed during colonization. This includes one secreted soluble CDA (Cda4) and five putatively glycosylphosphatidylinositol (GPI)-anchored CDAs, of which Cda7 belongs to a new class of fungal CDAs. Here, we provide a comprehensive functional study of the entire family. While budding cells of U. maydis showed a discrete pattern of chitosan staining, biotrophic hyphae appeared surrounded by a chitosan layer. We purified all six active CDAs and show their activity on different chitin substrates. Single as well as multiple cda mutants were generated and revealed a virulence defect for mutants lacking cda7. We implicated cda4 in production of the chitosan layer surrounding biotrophic hyphae and demonstrated that the loss of this layer does not reduce virulence. By combining different cda mutations, we detected redundancy as well as specific functions for certain CDAs. Specifically, certain combinations of mutations significantly affected virulence concomitantly with reduced adherence, appressorium formation, penetration, and activation of plant defenses. Attempts to inactivate all seven cda genes simultaneously were unsuccessful, and induced depletion of cda2 in a background lacking the other six cda genes illustrated an essential role of chitosan for cell wall integrity.

MC7

Chitin deacetylase (CDA) can hydrolyze the acetamido group of chitin polymers and its deacetylated derivatives to produce chitosan, an industrially important biopolymer. Compared with traditional chemical methods, biocatalysis by CDA is more environment-friendly and easy to control. However, most reported CDA-producing microbial strains show low CDA producing capabilities. Thus, the enhancement of CDA production has always been a challenge. In this study, we report co-culture fermentation to significantly promote the CDA production of Rhodococcus equi CGMCC14861 chitin deacetylase (ReCDA). Due to co-culture fermentation with Staphylococcus sp. MC7, ReCDA yield increased to 21.74 times that of pure culture of R. equi. Additionally, the enhancement was demonstrated to be cell-independent by adding cell-free extracts and the filtrate obtained by 10 kDa ultrafiltration of Staphylococcus sp. MC7. By preliminary characterization, we found extracellular, thermosensitive signal substances produced by Staphylococcus that were less than 10 kDa. We investigated the mechanism of promotion of ReCDA production by transcriptomic analysis. The data showed that 328 genes were upregulated and 1,258 genes were downregulated. The transcription level of the gene encoding ReCDA increased 2.3-fold. These findings provide new insights into the research of co-culture fermentation for the production of CDA and quorum sensing regulation.

Preparation of Defined Chitosan Oligosaccharides Using Chitin Deacetylases

During the past decade, detailed studies using well-defined 'second generation' chitosans have amply proved that both their material properties and their biological activities are dependent on their molecular structure, in particular on their degree of polymerisation (DP) and their fraction of acetylation (F_A). Recent evidence suggests that the pattern of acetylation (PA), i.e., the sequence of acetylated and non-acetylated residues along the linear polymer, is equally important, but chitosan polymers with defined, non-random PA are not yet available. One way in which the PA will influence the bioactivities of chitosan polymers is their enzymatic degradation by sequence-dependent chitosan hydrolases present in the target tissues. The PA of the polymer substrates in conjunction with the subsite preferences of the hydrolases determine the type of oligomeric products and the kinetics of their production and further degradation. Thus, the bioactivities of chitosan polymers will at least in part be carried by the chitosan oligomers produced from them, possibly through their interaction with pattern recognition receptors in target cells. In contrast to polymers, partially acetylated chitosan oligosaccharides (paCOS) can be fully characterised concerning their DP, F_A, and PA, and chitin deacetylases (CDAs) with different and known regio-selectivities are currently emerging as efficient tools to produce fully defined paCOS in quantities sufficient to probe their bioactivities. In this review, we describe the current state of the art on how CDAs can be used in forward and reverse mode to produce all of the possible paCOS dimers, trimers, and tetramers, most of the pentamers and many of the hexamers. In addition, we describe the biotechnological production of the required fully acetylated and fully deacetylated oligomer substrates, as well as the purification and characterisation of the paCOS products.

Evolutionary analysis and protein family classification of chitin deacetylases in Cryptococcus neoformans

Cryptococcus neoformans is an opportunistic fungal pathogen causing cryptococcal meningoencephalitis. Interestingly, the cell wall of C. neoformans contains chitosan, which is critical for its virulence and persistence in the mammalian host. C. neoformans (H99) has three chitin deacetylases (CDAs), which convert chitin to chitosan. Herein, the classification of the chitin-related protein (CRP) family focused on cryptococcal CDAs was analyzed by phylogenetics, evolutionary pressure (d_N/d_S), and 3D modeling. A phylogenetic tree of 110 CRPs revealed that they can be divided into two clades, CRP I and II with bootstrap values (> 99%). CRP I clade comprises five groups (Groups 1-5) with a total of 20 genes, while CRP II clade comprises sixteen groups (Groups 6-21) with a total of 90 genes. CRP I comprises only fungal CDAs, including all three C. neoformans CDAs, whereas CRP II comprises diverse CDAs from fungi, bacteria, and amoeba, along with other carbohydrate esterase 4 family proteins. All CDAs have the signal peptide, except those from group 11. Notably, CDAs with the putative O-gycosylation site possess either the glycosylphosphatidylinositol (GPI)-anchor motif for CRP I or the chitin-binding domain (CBD) for CRP II, respectively. This evolutionary conservation strongly indicates that the O-glycosylation modification and the presence of either the GPI-anchor motif or the chitin-binding domain is important for fungal CDAs to function efficiently at the cell surface. This study reveals that C. neoformans CDAs carrying GPI anchors have evolved divergently from fungal and bacterial CDAs, providing new insights into evolution and classification of CRP family.

Chitin deacetylase: A potential target for Mythimna separata (Walker) control

Chitin deacetylase (CDA) is a hydrolytic enzyme that modifies chitin into chitosan in the body of insects. In this study, we obtained a full-length complementary DNA sequence (MsCDA1) from the oriental armyworm Mythimna separata by high-throughput sequencing. MsCDA1 is 1,952 bp long and includes 1,620 bp open reading frame encoding 539 amino acids. Analysis by quantitative real time polymerase chain reaction showed that MsCDA1 expression was higher at the adult stage than at earlier developmental stages. MsCDA1 was expressed in all larval tissues examined, in which the highest expression level was found in the midgut. The RNA interference (RNAi) suppressed MsCDA1 expression levels at 12, 24, and 48 hr after injection of double-stranded RNA (1-4 μg per larva) specific to MsCDA1. Under RNAi condition, CDA enzyme activity was significantly reduced and changes an ultramicroscopic structure of M. separata peritrophic matrix especially in its microfibrillar organization exhibiting loose network. In contrast, the surface of the peritrophic matrix was relatively smooth and well organized at control or low RNAi conditions. Moreover, RNAi of MsCDA1 expression impaired larval growth and development, occasionally leading to larval death. These results demonstrate that MsCDA1 plays a crucial role in maintaining peritrophic matrix integrity in M. separata.

Role of Chitin Deacetylase 1 in the Molting and Metamorphosis of the Cigarette Beetle Lasioderma serricorne

Chitin deacetylases (CDAs) are chitin-modifying enzymes known to play vital roles in insect metamorphosis and development. In this study, we identified and characterized a chitin deacetylase1 gene (LsCDA1) from the cigarette beetle Lasioderma serricorne. LsCDA1 contains a 1614 bp open reading frame encoding a protein of 537 amino acids that includes domain structures typical of CDAs. LsCDA1 was mainly expressed in the late larval and late pupal stages. In larval tissues, the highest level of LsCDA1 was detected in the integument. The expression of LsCDA1 was induced by 20-hydroxyecdysone (20E) in vivo, and it was significantly suppressed by knocking down the expression of ecdysteroidogenesis genes and 20E signaling genes. RNA interference (RNAi)-aided silencing of LsCDA1 in fifth-instar larvae prevented the larval–pupal molt and caused 75% larval mortality. In the late pupal stage, depletion of LsCDA1 resulted in the inhibition of pupal growth and wing abnormalities, and the expression levels of four wing development-related genes (LsDY, LsWG, LsVG, and LsAP) were dramatically decreased. Meanwhile, the chitin contents of LsCDA1 RNAi beetles were significantly reduced, and expressions of three chitin synthesis pathway genes (LsTRE1, LsUAP1, and LsCHS1) were greatly decreased. The results suggest that LsCDA1 is indispensable for larval–pupal and pupal–adult molts, and that it is a potential target for the RNAi-based control of L. serricorne.

What Are the Functions of Chitin Deacetylases in Aspergillus fumigatus?

Deacetylation of chitin by chitin deacetylases (Cda) results in the formation of chitosan. Chitosan, a polymer of β1,4 linked glucosamine, plays multiple roles in the function of the fungal cell wall, including virulence and evasion of host immune responses. In this study, the roles of chitosan and putative CDAs in cell wall structure and virulence of Aspergillus fumigatus were investigated. Low levels of chitosan were found in the conidial and cell wall of A. fumigatus. Seven putative CDA genes were identified, disrupted and the phenotype of the single mutants and the septuple mutants were investigated. No alterations in fungal cell wall chitosan levels, changes in fungal growth or alterations in virulence were detected in the single or septuple Δcda1-7 mutant strains. Collectively, these results suggest that chitosan is a minority component of the A. fumigatus cell wall, and that the seven candidate Cda proteins do not play major roles in fungal cell wall synthesis or virulence. However, Cda2 is involved in conidiation, suggesting that this enzyme may play a role in N-acetyl-glucosamine metabolism.

Enzymatic Modification of Native Chitin and Conversion to Specialty Chemical Products

Chitin is one of the most abundant biomolecules on earth, occurring in crustacean shells and cell walls of fungi. While the polysaccharide is threatening to pollute coastal ecosystems in the form of accumulating shell-waste, it has the potential to be converted into highly profitable derivatives with applications in medicine, biotechnology, and wastewater treatment, among others. Traditionally this is still mostly done by the employment of aggressive chemicals, yielding low quality while producing toxic by-products. In the last decades, the enzymatic conversion of chitin has been on the rise, albeit still not on the same level of cost-effectiveness compared to the traditional methods due to its multi-step character. Another severe drawback of the biotechnological approach is the highly ordered structure of chitin, which renders it nigh impossible for most glycosidic hydrolases to act upon. So far, only the Auxiliary Activity 10 family (AA10), including lytic polysaccharide monooxygenases (LPMOs), is known to hydrolyse native recalcitrant chitin, which spares the expensive first step of chemical or mechanical pre-treatment to enlarge the substrate surface. The main advantages of enzymatic conversion of chitin over conventional chemical methods are the biocompability and, more strikingly, the higher product specificity, product quality, and yield of the process. Products with a higher M_w due to no unspecific depolymerisation besides an exactly defined degree and pattern of acetylation can be yielded. This provides a new toolset of thousands of new chitin and chitosan derivatives, as the physio-chemical properties can be modified according to the desired application. This review aims to provide an overview of the biotechnological tools currently at hand, as well as challenges and crucial steps to achieve the long-term goal of enzymatic conversion of native chitin into specialty chemical products.

Can we make Chitosan by Enzymatic Deacetylation of Chitin?

Chitin, an insoluble linear polymer of β-1,4-N-acetyl-d-glucosamine (GlcNAc; A), can be converted to chitosan, a soluble heteropolymer of GlcNAc and d-glucosamine (GlcN; D) residues, by partial deacetylation. In nature, deacetylation of chitin is catalyzed by enzymes called chitin deacetylases (CDA) and it has been proposed that CDAs could be used to produce chitosan. In this work, we show that CDAs can remove up to approximately 10% of N-acetyl groups from two different (α and β) chitin nanofibers, but cannot produce chitosan.

Enzymatic Modifications of Chitin, Chitosan, and Chitooligosaccharides

Chitin and its N-deacetylated derivative chitosan are two biological polymers that have found numerous applications in recent years, but their further deployment suffers from limitations in obtaining a defined structure of the polymers using traditional conversion methods. The disadvantages of the currently used industrial methods of chitosan manufacturing and the increasing demand for a broad range of novel chitosan oligosaccharides (COS) with a fully defined architecture increase interest in chitin and chitosan-modifying enzymes. Enzymes such as chitinases, chitosanases, chitin deacetylases, and recently discovered lytic polysaccharide monooxygenases had attracted considerable interest in recent years. These proteins are already useful tools toward the biotechnological transformation of chitin into chitosan and chitooligosaccharides, especially when a controlled non-degradative and well-defined process is required. This review describes traditional and novel enzymatic methods of modification of chitin and its derivatives. Recent advances in chitin processing, discovery of increasing number of new, well-characterized enzymes and development of genetic engineering methods result in rapid expansion of the field. Enzymatic modification of chitin and chitosan may soon become competitive to conventional conversion methods.

LmCDA1 organizes the cuticle by chitin deacetylation in Locusta migratoria

Cells produce an extracellular matrix (ECM) with a stereotypic organization that is important for tissue function. The insect cuticle is a layered ECM that mainly consists of the polysaccharide chitin and associated proteins adopting a quasi-crystalline structure. Our understanding of the molecular mechanisms deployed during construction of the highly ordered protein-chitin ECM so far is limited. In this study, we report on the role of the chitin deacetylase 1 (LmCDA1) in the organization of the protein-chitin ECM in the migratory locust Locusta migratoria, and LmCDA1 localizes predominantly to the apical tier of the protein-chitin ECM, but it is also found in lower regions. Reduction of LmCDA1 function correlates with lower amounts of chitin and impedes conversion of chitin to chitosan by deacetylation. Establishment of the quasi-crystalline architecture of the protein-chitin ECM is, however, independent of LmCDA1 activity, but it is dependent on another chitin deacetylase, LmCDA2, which has no detectable effects on chitin deacetylation and, as shown previously, no influence on chitin content. Our data reveal that LmCDA1 and LmCDA2 act in parallel and independently from each other in defining the dimensions of the cuticle. Both enzymes are non-uniformly distributed within the protein-chitin matrix, suggesting a site-autonomous function.

Comparative characterization of putative chitin deacetylases from Phaeodactylum tricornutum and Thalassiosira pseudonana highlights the potential for distinct chitin-based metabolic processes in diatoms

Chitin is generally considered to be present in centric diatoms but not in pennate species. Many aspects of chitin biosynthetic pathways have not been explored in diatoms. We retrieved chitin metabolic genes from pennate (Phaeodactylum tricornutum) and centric (Thalassiosira pseudonana) diatom genomes. Chitin deacetylase (CDA) genes from each genome (PtCDA and TpCDA) were overexpressed in P. tricornutum. We performed comparative analysis of their sequence structure, phylogeny, transcriptional profiles, localization and enzymatic activities. The chitin relevant proteins show complex subcellular compartmentation. PtCDA was likely acquired by horizontal gene transfer from prokaryotes, whereas TpCDA has closer relationships with sequences in Opisthokonta. Using transgenic P. tricornutum lines expressing CDA-green fluorescent protein (GFP) fusion proteins, PtCDA predominantly localizes to Golgi apparatus whereas TpCDA localizes to endoplasmic reticulum/chloroplast endoplasmic reticulum membrane. CDA-GFP overexpression upregulated the transcription of chitin synthases and potentially enhanced the ability of chitin synthesis. Although both CDAs are active on GlcNAc₅ , TpCDA is more active on the highly acetylated chitin polymer DA60. We have addressed the ambiguous characters of CDAs from P. tricornutum and T. pseudonana. Differences in localization, evolution, expression and activities provide explanations underlying the greater potential of centric diatoms for chitin biosynthesis. This study paves the way for in vitro applications of novel CDAs.

Structural and biochemical insights into the catalytic mechanisms of two insect chitin deacetylases of the carbohydrate esterase 4 family

Insect chitin deacetylases (CDAs) catalyze the removal of acetyl groups from chitin and modify this polymer during its synthesis and reorganization. CDAs are essential for insect survival and therefore represent promising targets for insecticide development. However, the structural and biochemical characteristics of insect CDAs have remained elusive. Here, we report the crystal structures of two insect CDAs from the silk moth Bombyx mori: BmCDA1, which may function in cuticle modification, and BmCDA8, which may act in modifying peritrophic membranes in the midgut. Both enzymes belong to the carbohydrate esterase 4 (CE4) family. Comparing their overall structures at 1.98–2.4 Å resolution with those from well-studied microbial CDAs, we found that two unique loop regions in BmCDA1 and BmCDA8 contribute to the distinct architecture of their substrate-binding clefts. These comparisons revealed that both BmCDA1 and BmCDA8 possess a much longer and wider substrate-binding cleft with a very open active site in the center than the microbial CDAs, including VcCDA from Vibrio cholerae and ArCE4A from Arthrobacter species AW19M34-1. Biochemical analyses indicated that BmCDA8 is an active enzyme that requires its substrates to occupy subsites 0, +1, and +2 for catalysis. In contrast, BmCDA1 also required accessory proteins for catalysis. To the best of our knowledge, our work is the first to unveil the structural and biochemical features of insect proteins belonging to the CE4 family.

Characterization of the Specific Mode of Action of a Chitin Deacetylase and Separation of the Partially Acetylated Chitosan Oligosaccharides

Partially acetylated chitosan oligosaccharides (COS), which consists of N-acetylglucosamine (GlcNAc) and glucosamine (GlcN) residues, is a structurally complex biopolymer with a variety of biological activities. Therefore, it is challenging to elucidate acetylation patterns and the molecular structure-function relationship of COS. Herein, the detailed deacetylation pattern of chitin deacetylase from Saccharomyces cerevisiae, ScCDA₂, was studied. Which solves the randomization of acetylation patterns during COS produced by chemical. ScCDA₂ also exhibits about 8% and 20% deacetylation activity on crystalline chitin and colloid chitin, respectively. Besides, a method for separating and detecting partially acetylated chitosan oligosaccharides by high performance liquid chromatography and electrospray ionization mass spectrometry (HPLC-ESI-MS) system has been developed, which is fast and convenient, and can be monitored online. Mass spectrometry sequencing revealed that ScCDA₂ produced COS with specific acetylation patterns of DAAA, ADAA, AADA, DDAA, DADA, ADDA and DDDA, respectively. ScCDA₂ does not deacetylate the GlcNAc unit that is closest to the reducing end of the oligomer furthermore ScCDA₂ has a multiple-attack deacetylation mechanism on chitin oligosaccharides. This specific mode of action significantly enriches the existing limited library of chitin deacetylase deacetylation patterns. This fully defined COS may be used in the study of COS structure and function.

Cryptococcus neoformans Cda1 and Its Chitin Deacetylase Activity Are Required for Fungal Pathogenesis

Cryptococcus neoformans is unique among fungal pathogens that cause disease in a mammalian host, as it secretes a polysaccharide capsule that hinders recognition by the host to facilitate its survival and proliferation. Even though it causes serious infections in immunocompromised hosts, reports of infection in hosts that are immunocompetent are on the rise. The cell wall of a fungal pathogen, its synthesis, composition, and pathways of remodelling are attractive therapeutic targets for the development of fungicides. Chitosan, a polysaccharide in the cell wall of C. neoformans is one such target, as it is critical for pathogenesis and absent in the host. The results we present shed light on the importance of one of the chitin deacetylases that synthesize chitosan during infection and further implicates chitosan as being a critical factor for the pathogenesis of C. neoformans.

Chitin is an essential component of the cell wall of Cryptococcus neoformans conferring structural rigidity and integrity under diverse environmental conditions. Chitin deacetylase genes encode the enyzmes (chitin deacetylases [Cdas]) that deacetylate chitin, converting it to chitosan. The functional role of chitosan in the fungal cell wall is not well defined, but it is an important virulence determinant of C. neoformans. Mutant strains deficient in chitosan are completely avirulent in a mouse pulmonary infection model. C. neoformans carries genes that encode three Cdas (Cda1, Cda2, and Cda3) that appear to be functionally redundant in cells grown under vegetative conditions. Here we report that C. neoformans Cda1 is the principal Cda responsible for fungal pathogenesis. Point mutations were introduced in the active site of Cda1 to generate strains in which the enzyme activity of Cda1 was abolished without perturbing either its stability or localization. When used to infect CBA/J mice, Cda1 mutant strains produced less chitosan and were attenuated for virulence. We further demonstrate that C. neoformans Cda genes are transcribed differently during a murine infection from what has been measured in vitro.

The Effect of Diet on Midgut and Resulting Changes in Infectiousness of AcMNPV Baculovirus in the Cabbage Looper, Trichoplusia ni

Insecticide resistance has been reported in many important agricultural pests, and alternative management methods are required. Baculoviruses qualify as an effective, yet environmentally benign, biocontrol agent but their efficacy against generalist herbivores may be influenced by diet. However, few studies have investigated the tritrophic interactions of plant, pest, and pathogen from both a gene expression and physiological perspective. Here we use microscopy and transcriptomics to examine how diet affects the structure of peritrophic matrix (PM) in Trichoplusia ni larvae and consequently their susceptibility to the baculovirus, AcMNPV. Larvae raised on potato leaves had lower transcript levels for chitinase and chitin deacetylase genes, and possessed a thicker and more multi-layered PM than those raised on cabbage or artificial diet, which could contribute to their significantly lower susceptibility to the baculovirus. The consequences of these changes underline the importance of considering dietary influences on pathogen susceptibility in pest management strategies.

Studies on the chitin/chitosan binding properties of six cuticular proteins analogous to peritrophin 3 from Bombyx mori

Chitin deacetylation is required to make the cuticle rigid and compact through chitin chain crosslinking. Thus it is presumed that specialized proteins are required to bind deacetylated chitin chains together. However, deacetylated-chitin binding proteins have not ever been reported. In a previous work, six cuticular proteins analogous to peritrophin 3 (CPAP3s) were found to be abundant in the moulting fluid of Bombyx mori. In this study, these BmCPAP3s (BmCPAP3-A1, BmCPAP3-A2, BmCPAP3-B, BmCPAP3-C, BmCPAP3-D1 and BmCPAP3-D2) were cloned and expressed in Escherichia coli and purified using metal-chelating affinity chromatography. Their binding activities demonstrated that although all of the BmCPAP3s showed similar binding abilities toward crystalline chitin and colloidal chitin, they differed in their affinities toward partially and fully deacetylated chitin. Amongst them, BmCPAP3-D1 exhibited the highest binding activity toward deacetylated chitin. The gene expression pattern of BmCPAP3-D1 was similar to BmCPAP3-A1 and BmCPAP3-C at most stages except that it was dramatically upregulated at the beginning of the pupa to adult transition stage. This work is the first report of a chitin-binding protein, BmCPAP3-D1, which exhibits high binding affinity to deacetylated chitin.

Production of chitin deacetylase by Aspergillus flavus in submerged conditions

Chitosan is a biopolymer obtained by deacetylation of chitin and has been proven to have various applications in industry and biomedicine. Deacetylation of chitin using the enzyme chitin deacetylase (CDA) is favorable in comparison to the hazardous chemical method involving strong alkali and high temperature. A fungal strain producing CDA was isolated from environmental samples collected from coastal regions of South Kerala, India. It was identified as Aspergillus flavus by morphological characteristics and ITS DNA analysis. Nutritional requirement for maximum production of CDA under submerged condition was optimized using statistical methods including Plackett-Burman and response surface methodology central composite design. A 5.98-fold enhancement in CDA production was attained in shake flasks when the fermentation process parameters were used at their optimum levels. The highest CDA activity was 57.69 ± 1.68 U under optimized bioprocess conditions that included 30 g L(-1) glucose, 40 g L(-1) yeast extract, 15 g L(-1) peptone, and 7 g L(-1) MgCl2 at initial media pH of 7 and incubation temperature of 32°C after 48 hr of incubation, while the unoptimized basal medium yielded 9.64 ± 2.04 U.

GUT GENES ASSOCIATED WITH THE PERITROPHIC MATRIX IN Reticulitermes flavipes (Blattodea: Rhinotermitidae): IDENTIFICATION AND CHARACTERIZATION

The peritrophic matrix (PM) is an acellular structure that lines the gut of most insects. It is an attractive target for pest management strategies because of its close involvement in digestive processes and role as a barrier against pathogens and toxins. The purpose of this study was to identify and characterize the genes that translate for principal components of the Reticulitermes flavipes PM. Genes encoding a gut chitin synthase (CHS), two proteins with peritrophin-A domains, and a chitin deacetylase were identified from an R. flavipes symbiont-free gut cDNA library, a pyrosequencing study of termite lignocellulose digestion, and a metatranscriptomic analysis of R. flavipes fed on agricultural biomass. Quantitative expression analysis of the identified genes, in the termite digestive tract, revealed that the transcripts coding for a CHS (RfCHSB) and the proteins with peritrophin-A domains (RfPPAD1 and RfPPAD2) were predominantly expressed in the midgut, suggesting an association with the PM. The peritrophin identity of the RfPPAD2 gene was confirmed by immunodetection of its translated peptide in the midgut and PM. The discovery and characterization of PM components of R. flavipes provides a basis for further investigation of the viability of this structure as a target for candidate termiticides.

Cloning and Tissue-Specific Expression of a Chitin Deacetylase Gene from Helicoverpa armigera (Lepidoptera: Noctuidae) and Its Response to Bacillus thuringiensis

Chitin deacetylases (CDAs) convert chitin into chitosan, the N-deacetylated form of chitin, which influences the mechanical and permeability properties of structures such as the cuticle and peritrophic matrices. In this article, a new CDA encoding gene, Hacda2, was cloned by reverse transcription-polymerase chain reaction method in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), with an open reading frame of 1,611 bp. The deduced protein composed of 536 amino acid residues with a signal peptide, a chitin-binding domain, a low-density lipoprotein receptor class A domain, and a polysaccharide deacetylase-like catalytic domain. The highest expression level of Hacda2 was detected in fat body among tissues tested in the fifth-instar larvae using real-time quantitative polymerase chain reaction method. Feeding of Bacillus thuringiensis (Bt) (Bacillales: Bacillaceae) diet changed the expression level of Hacda1, Hacda2, Hacda5a, and Hacda5b significantly and differentially in the third-instar larvae. Hacda5a and Hacda5b expression were initially down-regulated and then up-regulated, whereas, the expression level of Hacda1 and Hacda2 was suppressed constantly postfeeding on Bt diet. These results suggested that HaCDAs may be involved in the response of H. armigera larvae to Bt and may be helpful to elucidate the roles of HaCDAs in the action of Bt cry toxin. The potential of HaCDAs to be used as synergists of Bt insecticidal protein needs to be further tested.

Chitin deacetylase family genes in the brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae)

Chitin deacetylases (CDAs) are enzymes required for one of the pathways of chitin degradation, in which chitosan is produced by the deacetylation of chitin. Bioinformatic investigations with genomic and transcriptomic databases identified four genes encoding CDAs in Nilaparvata lugens (NlCDAs). Phylogenetic analysis showed that insect CDAs were clustered into five major groups. Group I, III and IV CDAs are found in all insect species, whereas the pupa-specific group II and gut-specific group V CDAs are not found in the plant-sap/blood-sucking hemimetabolous species from Hemiptera and Anoplura. The developmental and tissue-specific expression patterns of four NlCDAs revealed that NlCDA3 was a gut-specific CDA, with high expression at all developmental stages; NlCDA1, NlCDA2 and NlCDA4 were highly expressed in the integument and peaked periodically during every moulting, which suggests their roles in chitin turnover of the insect old cuticle. Lethal phenotypes of cuticle shedding failure and high mortality after the injection of double-stranded RNAs (dsRNAs) for NlCDA1, NlCDA2 and NlCDA4 provide further evidence for their functions associated with moulting. No observable morphological and internal structural abnormality was obtained in insects treated with dsRNA for gut-specific NlCDA3.

Bioproduction of chitooligosaccharides: present and perspectives

Chitin and chitosan oligosaccharides (COS) have been traditionally obtained by chemical digestion with strong acids. In light of the difficulties associated with these traditional production processes, environmentally compatible and reproducible production alternatives are desirable. Unlike chemical digestion, biodegradation of chitin and chitosan by enzymes or microorganisms does not require the use of toxic chemicals or excessive amounts of wastewater. Enzyme preparations with chitinase, chitosanase, and lysozymeare primarily used to hydrolyze chitin and chitosan. Commercial preparations of cellulase, protease, lipase, and pepsin provide another opportunity for oligosaccharide production. In addition to their hydrolytic activities, the transglycosylation activity of chitinolytic enzymes might be exploited for the synthesis of desired chitin oligomers and their derivatives. Chitin deacetylase is also potentially useful for the preparation of oligosaccharides. Recently, direct production of oligosaccharides from chitin and crab shells by a combination of mechanochemical grinding and enzymatic hydrolysis has been reported. Together with these, other emerging technologies such as direct degradation of chitin from crustacean shells and microbial cell walls, enzymatic synthesis of COS from small building blocks, and protein engineering technology for chitin-related enzymes have been discussed as the most significant challenge for industrial application.

Optimization of medium components for production of chitin deacetylase by Bacillus amyloliquefaciens Z7, using response surface methodology

Plackett-Burman design and Box-Behnken response surface methodology (RSM) was employed to optimize the medium components for the chitin deacetylase (CDA) activity from Bacillus amyloliquefaciens Z7. Plackett-Burman design was applied to determine the specific medium components affecting CDA activity and found that starch, chitin and MgSO4 were critical in augmenting CDA activity. These significant parameters were further optimized using Box-Behnken RSM and the optimum concentrations of starch, chitin and MgSO4 were found to be 24.4, 8.8 and 0.19 g/L, respectively. The optimum medium composition was chitin 8.8 g/L, starch 24.4 g/L, yeast extract 10g/L, MgSO4 0.19 g/L, K2HPO4 0.3 g/L and NaCl 5 g/L. Under these optimal conditions, the CDA activity of Bacillus amyloliquefaciens Z7 increased distinctly from 18.75 to 27.48 U/mL (46.6% increase in total yield).

In vitro and in vivo application of RNA interference for targeting genes involved in peritrophic matrix synthesis in a lepidopteran system

The midgut of most insects is lined with a semipermeable acellular tube, the peritrophic matrix (PM), composed of chitin and proteins. Although various genes encoding PM proteins have been characterized, our understanding of their roles in PM structure and function is very limited. One promising approach for obtaining functional information is RNA interference, which has been used to reduce the levels of specific mRNAs using double-stranded RNAs administered to larvae by either injection or feeding. Although this method is well documented in dipterans and coleopterans, reports of its success in lepidopterans are varied. In the current study, the silencing midgut genes encoding PM proteins (insect intestinal mucin 1, insect intestinal mucin 4, PM protein 1) and the chitin biosynthetic or modifying enzymes (chitin synthase-B and chitin deacetylase 1) in a noctuid lepidopteran, Mamestra configurata, was examined in vitro and in vivo. In vitro studies in primary midgut epithelial cell preparations revealed an acute and rapid silencing (by 24 h) for the gene encoding chitin deacetylase 1 and a slower rate of silencing (by 72 h) for the gene encoding PM protein 1. Genes encoding insect intestinal mucins were slightly silenced by 72 h, whereas no silencing was detected for the gene encoding chitin synthase-B. In vivo experiments focused on chitin deacetylase 1, as the gene was silenced to the greatest extent in vitro. Continuous feeding of neonates and fourth instar larvae with double-stranded RNA resulted in silencing of chitin deacetylase 1 by 24 and 36 h, respectively. Feeding a single dose to neonates also resulted in silencing by 24 h. The current study demonstrates that genes encoding PM proteins can be silenced and outlines conditions for RNA interference by per os feeding in lepidopterans.

Chitin deacetylases: properties and applications

Chitin deacetylases, occurring in marine bacteria, several fungi and a few insects, catalyze the deacetylation of chitin, a structural biopolymer found in countless forms of marine life, fungal cell and spore walls as well as insect cuticle and peritrophic matrices. The deacetylases recognize a sequence of four GlcNAc units in the substrate, one of which undergoes deacetylation: the resulting chitosan has a more regular deacetylation pattern than a chitosan treated with hot NaOH. Nevertheless plain chitin is a poor substrate, but glycolated, reprecipitated or depolymerized chitins are good ones. The marine Vibrio sp. colonize the chitin particles and decompose the chitin thanks to the concerted action of chitinases and deacetylases, otherwise they could not tolerate chitosan, a recognized antibacterial biopolymer. In fact, chitosan is used to prevent infections in fishes and crustaceans. Considering that chitin deacetylases play very important roles in the biological attack and defense systems, they may find applications for the biological control of fungal plant pathogens or insect pests in agriculture and for the biocontrol of opportunistic fungal human pathogens.