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

Insights into midgut cell types and their crucial role in antiviral immunity in the lepidopteran model Bombyx mori

The midgut, a vital component of the digestive system in arthropods, serves as an interface between ingested food and the insect's physiology, playing a pivotal role in nutrient absorption and immune defense mechanisms. Distinct cell types, including columnar, enteroendocrine, goblet and regenerative cells, comprise the midgut in insects and contribute to its robust immune response. Enterocytes/columnar cells, the primary absorptive cells, facilitate the immune response through enzyme secretions, while regenerative cells play a crucial role in maintaining midgut integrity by continuously replenishing damaged cells and maintaining the continuity of the immune defense. The peritrophic membrane is vital to the insect's innate immunity, shielding the midgut from pathogens and abrasive food particles. Midgut juice, a mixture of digestive enzymes and antimicrobial factors, further contributes to the insect's immune defense, helping the insect to combat invading pathogens and regulate the midgut microbial community. The cutting-edge single-cell transcriptomics also unveiled previously unrecognized subpopulations within the insect midgut cells and elucidated the striking similarities between the gastrointestinal tracts of insects and higher mammals. Understanding the intricate interplay between midgut cell types provides valuable insights into insect immunity. This review provides a solid foundation for unraveling the complex roles of the midgut, not only in digestion but also in immunity. Moreover, this review will discuss the novel immune strategies led by the midgut employed by insects to combat invading pathogens, ultimately contributing to the broader understanding of insect physiology and defense mechanisms.

An overview of viral chitinases: General properties and biotechnological potential

Chitin is a biopolymer profusely present in nature and of pivotal importance as a structural component in cells. It is degraded by chitinases, enzymes naturally produced by different organisms. Chitinases are proteins enrolled in many cellular mechanisms, including the remodeling process of the fungal cell wall, the cell growth process, the autolysis of filamentous fungi, and cell separation of yeasts, among others. These enzymes also have properties with different biotechnological applications. They are used to produce polymers, for biological control, biofilm formation, and as antitumor and anti-inflammatory target molecules. Chitinases are classified into different glycoside hydrolase (GH) families and are widespread in microorganisms, including viruses. Among them, the GH18 family is highly predominant in the viral genomes, being present and active enzymes in baculoviruses and nucleocytoplasmic large DNA viruses (NCLDV), especially chloroviruses from the Phycodnaviridae family. These viral enzymes contain one or more GH domains and seem to be involved during the viral replication cycle. Curiously, only a few DNA viruses have these enzymes, and studying their properties could be a key feature for biological and biotechnological novelties. Here, we provide an overview of viral chitinases and their probable function in viral infection, showing evidence of at least two distinct origins for these enzymes. Finally, we discuss how these enzymes can be applied as biotechnological tools and what one can expect for the coming years on these GHs.

Diversity of transgenes in sustainable management of insect pests

Insecticidal transgenes, when incorporated and expressed in plants, confer resistance against insects by producing several products having insecticidal properties. Protease inhibitors, lectins, amylase inhibitors, and chitinase genes are associated with the natural defenses developed by plants to counter insect attacks. Several toxin genes are also derived from spiders and scorpions for protection against insects. Bacillus thuringiensis Berliner is a microbial source of insecticidal toxins. Several methods have facilitated the large-scale production of transgenic plants. Bt-derived cry, cyt, vip, and sip genes, plant-derived genes such as lectins, protease inhibitors, and alpha-amylase inhibitors, insect cell wall-degrading enzymes like chitinase and some proteins like arcelins, plant defensins, and ribosome-inactivating proteins have been successfully utilized to impart resistance to insects. Besides, transgenic plants expressing double-stranded RNA have been developed with enhanced resistance. However, the long-term effects of transgenes on insect resistance, the environment, and human health must be thoroughly investigated before they are made available for commercial planting. In this chapter, the present status, prospects, and future scope of transgenes for insect pest management have been summarized and discussed.

Chitinases as key virulence factors in microbial pathogens: Understanding their role and potential as therapeutic targets

Chitinases are crucial for the survival of bacterial and fungal pathogens both during host infection and outside the host in the environment. Chitinases facilitate adhesion onto host cells, act as virulence factors during infection, and provide protection from the host immune system, making them crucial factors in the survival of microbial pathogens. Understanding the mechanisms behind chitinase action is beneficial to design novel therapeutics to control microbial infections. This review explores the role of chitinases in the pathogenesis of bacterial, fungal, and viral infections. The mechanisms underlying the action of chitinases of bacterial, fungal, and viral pathogens in host cells are thoroughly reviewed. The evolutionary relationships between chitinases of various bacterial, fungal, and viral pathogens are discussed to determine their involvement in processes, such as adhesion and host immune system modulation. Gaining a better understanding of the distribution and activity of chitinases in these microbial pathogens can help elucidate their role in the invasion and infection of host cells.

A Novel EGFR Targeted Immunotoxin Based on Cetuximab and Type 1 RIP Quinoin Overcomes the Cetuximab Resistance in Colorectal Cancer Cells

Cetuximab is a monoclonal antibody blocking the epidermal growth factor receptor (EGFR) in metastatic colorectal cancer (mCRC). However, cetuximab treatment has no clinical benefits in patients affected by mCRC with KRAS mutation or in the presence of constitutive activation of signalling pathways acting downstream of the EGFR. The aim of this study was to improve cetuximab's therapeutic action by conjugating cetuximab with the type 1 ribosome inactivating protein (RIP) quinoin isolated from quinoa seeds. A chemical conjugation strategy based on the use of heterobifunctional reagent succinimidyl 3-(2-pyridyldithio)propionate (SPDP) was applied to obtain the antibody-type 1 RIP chimeric immunoconjugate. The immunotoxin was then purified by chromatographic technique, and its enzymatic action was evaluated compared to quinoin alone. Functional assays were performed to test the cytotoxic action of the quinoin cetuximab immunoconjugate against the cetuximab-resistant GEO-CR cells. The novel quinoin cetuximab immunoconjugate showed a significant dose-dependent cytotoxicity towards GEO-CR cells, achieving IC50 values of 27.7 nM (~5.0 μg/mL) at 72 h compared to cetuximab (IC50 = 176.7 nM) or quinoin (IC50 = 149.3 nM) alone assayed in equimolar amounts. These results support the therapeutic potential of quinoin cetuximab immunoconjugate for the EGFR targeted therapy, providing a promising candidate for further development towards clinical use in the treatment of cetuximab-resistant metastatic colorectal cancer.

Isolation, Characterization and Biological Action of Type-1 Ribosome-Inactivating Proteins from Tissues of Salsola soda L

Ribosome-inactivating proteins (RIPs) are known as RNA N-glycosylases. They depurinate the major rRNA, damaging ribosomes and inhibiting protein synthesis. Here, new single-chain (type-1) RIPs named sodins were isolated from the seeds (five proteins), edible leaves (one protein) and roots (one protein) of Salsola soda L. Sodins are able to release Endo's fragment when incubated with rabbit and yeast ribosomes and inhibit protein synthesis in cell-free systems (IC₅₀ = 4.83-79.31 pM). In addition, sodin 5, the major form isolated from seeds, as well as sodin eL and sodin R, isolated from edible leaves and roots, respectively, display polynucleotide:adenosine glycosylase activity and are cytotoxic towards the Hela and COLO 320 cell lines (IC₅₀ = 0.41-1200 nM), inducing apoptosis. The further characterization of sodin 5 reveals that this enzyme shows a secondary structure similar to other type-1 RIPs and a higher melting temperature (Tm = 76.03 ± 0.30 °C) and is non-glycosylated, as other sodins are. Finally, we proved that sodin 5 possesses antifungal activity against Penicillium digitatum.

Myoglobin from Atlantic and Tinker mackerels: Purification, characterization and its possible use as a molecular marker

Here, we report the characterization (purification, autoxidation rate, pseudoperoxidase activity) and amino acid sequence determination of S. scombrus (Atlantic mackerel) and S. colias (Tinker mackerel) mioglobins (Mbs), considering the increasing consumption of fresh and canned mackerel meat and Mb implication in meat storage (e.g.: browning and lipid oxidation). We found that Atlantic mackerel Mb has major autoxidation rate (0.204 ± 0.013 h^-1) compared to Tinker mackerel Mb (0.140 ± 0.009 h^-1), while the pseudoperoxidase activity is major for Tinker mackerel (K_m: 87.71 ± 7.19 μM; k_cat: 0.32 s^-1) Mb with respect to Atlantic mackerel (K_m: 96.08 ± 6.91 μM; k_cat: 0.50 s^-1). These functional differences are confirmed by primary structure determination, in which six amino acid substitutions are found, with the first N-terminal amino acid residue acetylated. Furthermore, we predicted by AphaFold 3D model both fish Mbs and used them to investigate the possible structural differences. In addition, phylogenetic analysis using Mb sequences from Scombridae family confirms that Atlantic and Tinker mackerels are two distinct species. Finally, an analytic qualitative RP-HPLC method to distinguish S. scombrus and S. colias specimens was developed considering the different retention times of the two mackerel apoMbs.

A Contemporary Appraisal on Impending Industrial and Agricultural Applications of Thermophilic-Recombinant Chitinolytic Enzymes from Microbial Sources

The ability of chitinases to degrade the second most abundant polymer, chitin, into potentially useful chitooligomers and chitin derivatives has not only rendered them fit for chitinous waste management but has also made them important from industrial point of view. At the same time, they have also been recognized to have an imperative role as promising biocontrol agents for controlling plant diseases. As thermostability is an important property for an industrially important enzyme, various bacterial and fungal sources are being exploited to obtain such stable enzymes. These stable enzymes can also play a role in agriculture by maintaining their stability under adverse environmental conditions for longer time duration when used as biocontrol agent. Biotechnology has also played its role in the development of recombinant chitinases with enhanced activity, thermostability, fungicidal and insecticidal activity via recombinant DNA techniques. Furthermore, a relatively new approach of generating pathogen-resistant transgenic plants has opened new ways for sustainable agriculture by minimizing the yield loss of valuable crops and plants. This review focuses on the potential applications of thermostable and recombinant microbial chitinases in industry and agriculture.

Ageritin-The Ribotoxin-like Protein from Poplar Mushroom (Cyclocybe aegerita) Sensitizes Primary Glioblastoma Cells to Conventional Temozolomide Chemotherapy

Here, we propose Ageritin, the prototype of the ribotoxin-like protein family, as an adjuvant treatment to control the growth of NULU and ZAR, two primary human glioblastoma cell lines, which exhibit a pharmacoresistance phenotype. Ageritin is able to inhibit NULU and ZAR growth with an IC50 of 0.53 ± 0.29 µM and 0.42 ± 0.49 µM, respectively. In this study, Ageritin treatment highlighted a macroscopic genotoxic response through the formation of micronuclei, which represents the morphological manifestation of genomic chaos induced by this toxin. DNA damage was not associated with either the deregulation of DNA repair enzymes (i.e., ATM and DNA-PK), as demonstrated by quantitative PCR, or reactive oxygen species. Indeed, the pretreatment of the most responsive cell line ZAR with the ROS scavenger N-acetylcysteine (NAC) did not follow the reverse cytotoxic effect of Ageritin, suggesting that this protein is not involved in cellular oxidative stress. Vice versa, Ageritin pretreatment strongly enhanced the sensitivity to temozolomide (TMZ) and inhibited MGMT protein expression, restoring the sensitivity to temozolomide. Overall, Ageritin could be considered as a possible innovative glioblastoma treatment, directly damaging DNA and downregulating the MGMT DNA repair protein. Finally, we verified the proteolysis susceptibility of Ageritin using an in vitro digestion system, and considered the future perspective use of this toxin as a bioconjugate in biomedicine.

The Structural Characterization and Antipathogenic Activities of Quinoin, a Type 1 Ribosome-Inactivating Protein from Quinoa Seeds

Quinoin is a type 1 ribosome-inactivating protein (RIP) we previously isolated from the seeds of pseudocereal quinoa (Chenopodium quinoa) and is known as a functional food for its beneficial effects on human health. As the presence of RIPs in edible plants could be potentially risky, here we further characterised biochemically the protein (complete amino acid sequence, homologies/differences with other RIPs and three-dimensional homology modeling) and explored its possible defensive role against pathogens. Quinoin consists of 254 amino acid residues, without cysteinyl residues. As demonstrated by similarities and homology modeling, quinoin preserves the amino acid residues of the active site (Tyr75, Tyr122, Glu177, Arg180, Phe181 and Trp206; quinoin numbering) and the RIP-fold characteristic of RIPs. The polypeptide chain of quinoin contains two N-glycosylation sites at Asn115 and Asp231, the second of which appears to be linked to sugars. Moreover, by comparative MALDI-TOF tryptic peptide mapping, two differently glycosylated forms of quinoin, named pre-quinoin-1 and pre-quinoin-2 (~0.11 mg/100 g and ~0.85 mg/100 g of seeds, respectively) were characterised. Finally, quinoin possesses: (i) strong antiviral activity, both in vitro and in vivo towards Tobacco Necrosis Virus (TNV); (ii) a growth inhibition effect on the bacterial pathogens of plants; and (iii) a slight antifungal effect against two Cryphonectria parasitica strains.

Recent advances in the bioprospection and applications of chitinolytic bacteria for valorization of waste chitin

One of the most abundant natural polymers on earth, chitin is a fibrous and structural polysaccharide, composed of N-acetyl-D-glucosamine. The biopolymer is the major structural constituent of fungi, arthropods, mollusks, nematodes, and some algae. The biodegradation of chitin is largely manifested by chitinolytic enzyme secreting organisms including bacteria, insects, and plants. Among them, bacterial chitinases represent the most promising, inexpensive, and sustainable source of proteins that can be employed for industrial-scale applications. To this end, the presented review comes at a timely moment to highlight the major sources of chitinolytic bacteria. It also discusses the potential pros and cons of prospecting bacterial chitinases that can be easily manipulated through genetic engineering. Additionally, we have elaborated the recent applications of the chitin thereby branding chitinases as potential candidates for biorefinery and biomedical research for eco-friendly and sustainable management of chitin waste in the environment.

Antimicrobial peptides from Capsicum chinense fruits: agronomic alternatives against phytopathogenic fungi

In recent years, the antimicrobial activity of peptides isolated from a wide variety of organs from plant species has been reported. However, a few studies have investigated the potential of antimicrobial peptides (AMPs) found in fruits, especially Capsicum chinense (pepper). The present study aimed to purify and characterize peptides from Capsicum chinense fruits and evaluate their inhibitory activities against different phytopathogenic fungi and also analyze the possible mechanisms of action involved in microbial inhibition. After fruit protein extraction and high-performance liquid chromatography (HPLC), different fractions were obtained, named F1 to F10. Peptides in the F4 and F5 fractions were sequenced and revealed similarity with the plant antimicrobial peptides like non-specific lipid transfer proteins and defensin-like peptide. The F4 and F5 fractions presented strong antimicrobial activity against the fungus Fusarium solani and Fusarium oxysporum, causing toxic effects on these fungi, leading to membrane permeabilization, endogenous reactive oxygen species increase, activation of metacaspase and loss of mitochondrial function.

Coffea canephora Peptides in Combinatorial Treatment with Fluconazole: Antimicrobial Activity against Phytopathogenic Fungus

The objective of the present study was to evaluate the antimicrobial activity of the Cc-LTP2 and Cc-GRP peptides isolated from Coffea canephora seeds and their possible synergistic activity with the azole drug fluconazole and characterize their mechanisms of action on cells of pathogenic fungi. Cc-LTP2 and Cc-GRP alone or in combination with 20 µg/mL of fluconazole were evaluated for their antimicrobial activity on the fungus Fusarium solani, and the effects of these peptides on the permeability of membranes and the induction of oxidative stress were determined. Our results show that these peptides at a concentration of 400 µg/mL combined with 20 µg/mL of fluconazole were able to inhibit the growth of the tested fungi, promote changes in their growth pattern, permeabilize the membrane, and induce reactive oxygen species (ROS). Some of these results were also observed with the peptides alone or with fluconazole alone, suggesting that the peptides act synergistically, promoting the potentiation of antimicrobial action. In this study, it was shown that Cc-LTP2 and Cc-GRP in combination with fluconazole were able to inhibit the growth of the fungus F. solani, to promote permeabilization of its membrane, and to induce the production of ROS, suggesting a combinatorial activity between the peptides and fluconazole.

Antimicrobial activity and mechanism of action of a thionin-like peptide from Capsicum annuum fruits and combinatorial treatment with fluconazole against Fusarium solani

Many Fusarium species are able to cause severe infections in plants as well as in animals and humans. Therefore, the discovery of new antifungal agents is of paramount importance. CaThi belongs to the thionins, which are cationic peptides with low molecular weights (∼5 kDa) that have toxic effects against various microorganisms. Herein, we study the mechanism of action of CaThi and its combinatory effect with fluconazole (FLC) against Fusarium solani. The mechanism of action of CaThi was studied by growth inhibition, viability, plasma membrane permeabilization, ROS induction, caspase activation, localization, and DNA binding capability, as assessed with Sytox green, DAB, FITC-VAD-FMK, CaThi-FITC, and gel shift assays. The combinatory effect of CaThi and FLC was assessed using a growth inhibition assay. Our results demonstrated that CaThi present a dose dependent activity and at the higher used concentration (50 µg mL^-1 ) inhibits 83% of F. solani growth, prevents the formation of hyphae, permeabilizes membranes, induces endogenous H₂ O₂ , activates caspases, and localizes intracellularly. CaThi combined with FLC, at concentrations that alone do not inhibit F. solani, result in 100% death of F. solani when combined. The data presented in this study demonstrate that CaThi causes death of F. solani via apoptosis; an intracellular target may also be involved. Combined treatment using CaThi and FLC is a strong candidate for studies aimed at improved targeting of F. solani. This strategy is of particular interest because it minimizes selection of resistant microorganisms.

A secreted chitinase-like protein (OsCLP) supports root growth through calcium signaling in Oryza sativa

Chitinases belong to a conserved protein family and play multiple roles in defense, development and growth regulation in plants. Here, we identified a secreted chitinase-like protein, OsCLP, which functions in rice growth. A T-DNA insertion mutant of OsCLP (osclp) showed significant retardation of root and shoot growth. A comparative proteomic analysis was carried out using root tissue of wild-type and the osclp mutant to understand the OsCLP-mediated rice growth retardation. Results obtained revealed that proteins related to glycolysis (phosphoglycerate kinase), stress adaption (chaperonin) and calcium signaling (calreticulin and CDPK1) were differentially regulated in osclp roots. Fura-2 molecular probe staining, which is an intracellular calcium indicator, and inductively coupled plasma-mass spectrometry (ICP-MS) analysis suggested that the intracellular calcium content was significantly lower in roots of osclp as compared with the wild-type. Exogenous application of Ca²⁺ resulted in successful recovery of both primary and lateral root growth in osclp. Moreover, overexpression of OsCLP resulted in improved growth with modified seed shape and starch structure; however, the overall yield remained unaffected. Taken together, our results highlight the involvement of OsCLP in rice growth by regulating the intracellular calcium concentrations.

Purification and Characterization of a Major Extracellular Chitinase from a Biocontrol Bacterium, Paenibacillus elgii HOA73

Chitinase-producing Paenibacillus elgii strain HOA73 has been used to control plant diseases. However, the antimicrobial activity of its extracellular chitinase has not been fully elucidated. The major extracellular chitinase gene (PeChi68) from strain HOA73 was cloned and expressed in Escherichia coli in this study. This gene had an open reading frame of 2,028 bp, encoding a protein of 675 amino acid residues containing a secretion signal peptide, a chitin-binding domain, two fibronectin type III domains, and a catalytic hydrolase domain. The chitinase (PeChi68) purified from recombinant E. coli exhibited a molecular mass of approximately 68 kDa on SDS-PAGE. Biochemical analysis indicated that optimum temperature for the actitvity of purified chitinase was 50ºC. However, it was inactivated with time when it was incubated at 40ºC and 50ºC. Its optimum activity was found at pH 7, although its activity was stable when incubated between pH 3 and pH 11. Heavy metals inhibited this chitinase. This purified chitinase completely inhibited spore germination of two Cladosporium isolates and partially inhibited germination of Botrytis cinerea spores. However, it had no effect on the spores of a Colletotricum isolate. These results indicate that the extracellular chitinase produced by P. elgii HOA73 might have function in limiting spore germination of certain fungal pathogens.

Intergeneric fusant development using chitinase preparation of Rhizopus stolonifer NCIM 880

Fungal chitinase have tremendous applications in biotech industries, with this approach we focused on extracellular chitinase from Rhizopus stolonifer NCIM 880 for the formation of fungal protoplasts. The maximum chitinase production reached after 24 h at 2.5% colloidal chitin concentration in presence of starch as an inducer. Chitinase was extracted efficiently at 65% cold acetone concentration and then purified by using DEAE-Cellulose column chromatography. Purified chitinase having molecular weight 22 kDa with single polypeptide chain was optimally active at pH 5.0 and temperature 30 °C. The purified chitinase revealed kinetic properties like Km 1.66 mg/ml and Vmax 769 mM/min. Crude chitinase extract efficiently formed protoplasts from A. niger, A. oryzae, T. viride and F. moniliforme. The formed protoplasts of A. niger and T. viride showed 70 and 66% regeneration frequency respectively. Further, intergeneric fusants were developed successfully and identified at molecular level using RNA profiling. Thus, this study could be useful for strain improvement of various fungi for biotechnological applications.

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.

Insight into the structural and functional features of myoglobin from Hystrix cristata L. and Rangifer tarandus L

Myoglobins (Mbs) from Hystrix cristata L. and Rangifer tarandus L. have been isolated and characterised.

Bacterial chitinase with phytopathogen control capacity from suppressive soil revealed by functional metagenomics

Plant disease caused by fungal pathogens results in vast crop damage globally. Microbial communities of soil that is suppressive to fungal crop disease provide a source for the identification of novel enzymes functioning as bioshields against plant pathogens. In this study, we targeted chitin-degrading enzymes of the uncultured bacterial community through a functional metagenomics approach, using a fosmid library of a suppressive soil metagenome. We identified a novel bacterial chitinase, Chi18H8, with antifungal activity against several important crop pathogens. Sequence analyses show that the chi18H8 gene encodes a 425-amino acid protein of 46 kDa with an N-terminal signal peptide, a catalytic domain with the conserved active site F¹⁷⁵DGIDIDWE¹⁸³, and a chitinase insertion domain. Chi18H8 was expressed (pGEX-6P-3 vector) in Escherichia coli and purified. Enzyme characterization shows that Chi18H8 has a prevalent chitobiosidase activity with a maximum activity at 35 °C at pH lower than 6, suggesting a role as exochitinase on native chitin. To our knowledge, Chi18H8 is the first chitinase isolated from a metagenome library obtained in pure form and which has the potential to be used as a candidate agent for controlling fungal crop diseases. Furthermore, Chi18H8 may also answer to the demand for novel chitin-degrading enzymes for a broad range of other industrial processes and medical purposes.

Immobilised peroxidases from Asparagus acutifolius L. seeds for olive mill waste water treatment

AaP-1-4 peroxidase fromA. acutifoliusL. was immobilised on Eupergit® CM; Eup-AaP-1-4 was proved to be able to remove (poly)phenols in olive mill waste water; Eup-AaP-1-4 is an economic source for removal phenols from industrial processes.

Chitinases: in agriculture and human healthcare

Biological control of phytopathogenic fungi and insects continues to inspire the research and development of environmentally friendly bioactive alternatives. Potentially lytic enzymes, chitinases can act as a biocontrol agent against agriculturally important fungi and insects. The cell wall in fungi and protective covers, i.e. cuticle in insects shares a key structural polymer, chitin, a β-1,4-linked N-acetylglucosamine polymer. Therefore, it is advantageous to develop a common biocontrol agent against both of these groups. As chitin is absent in plants and mammals, targeting its metabolism will signify an eco-friendly strategy for the control of agriculturally important fungi and insects but is innocuous to mammals, plants, beneficial insects and other organisms. In addition, development of chitinase transgenic plant varieties probably holds the most promising method for augmenting agricultural crop protection and productivity, when properly integrated into traditional systems. Recently, human proteins with chitinase activity and chitinase-like proteins were identified and established as biomarkers for human diseases. This review covers the recent advances of chitinases as a biocontrol agent and its various applications including preparation of medically important chitooligosaccharides, bioconversion of chitin as well as in implementing chitinases as diagnostic and prognostic markers for numerous diseases and the prospect of their future utilization.

A novel malate dehydrogenase from Ceratonia siliqua L. seeds with potential biotechnological applications

A novel malate dehydrogenase (MDH; EC 3.1.1.1.37), hereafter MDHCs, from Ceratonia siliqua seeds, commonly known as Carob tree, was purified by using ammonium sulphate precipitation, ion exchange chromatography on SteamLine SP and gel-filtration. The molecular mass of the native protein, obtained by analytical gel-filtration, was about 65 kDa, whereas, by using SDS-PAGE analysis, with and without reducing agent, was 34 kDa. The specific activity of purified MDHCs (0.25 mg/100 g seeds) was estimated to be 188 U/mg. The optimum activity of the enzyme is at pH 8.5, showing a decrease in the presence of Ca(2+), Mg(2+) and NaCl. The N-terminal sequence of the first 20 amino acids of MDHCs revealed 95 % identity with malate dehydrogenase from Medicago sativa L. Finally, the enzymatic activity of MDHCs was preserved even after absorption onto a PVDF membrane. To our knowledge, this is the first contribution to the characterization of an enzyme from Carob tree sources.

Mice orally immunized with a transgenic plant expressing the glycoprotein of Crimean-Congo hemorrhagic fever virus

While Crimean-Congo hemorrhagic fever (CCHF) has a high mortality rate in humans, the associated virus (CCHFV) does not induce clinical symptoms in animals, but animals play an important role in disease transmission to humans. Our aim in this study was to examine the immunogenicity of the CCHFV glycoprotein when expressed in the root and leaf of transgenic plants via hairy roots and stable transformation of tobacco plants, respectively. After confirmatory analyses of transgenic plant lines and quantification of the expressed glycoprotein, mice were either fed with the transgenic leaves or roots, fed the transgenic plant material and injected subcutaneously with the plant-made CCHFV glycoprotein (fed/boosted), vaccinated with an attenuated CCHF vaccine (positive control), or received no treatment (negative control). All immunized groups had a consistent rise in anti-glycoprotein IgG and IgA antibodies in their serum and feces, respectively. The mice in the fed/boosted group showed a significant rise in specific IgG antibodies after a single boost. Our results imply that oral immunization of animals with edible materials from transgenic plants is feasible, and further assessments are under way. In addition, while the study of CCHF is challenging, our protocol should be further used to study CCHFV infection in the knockout mouse model and virus neutralization assays in biosafety level 4 laboratories.