Showing papers on "Chitinase published in 2007"
TL;DR: It is shown that chitin induces the accumulation in tissue of IL-4-expressing innate immune cells, including eosinophils and basophils, when given to mice, and this process can be negatively regulated by a vertebrate chit inase.
Abstract: Allergic and parasitic worm immunity is characterized by infiltration of tissues with interleukin (IL)-4- and IL-13-expressing cells, including T-helper-2 cells, eosinophils and basophils. Tissue macrophages assume a distinct phenotype, designated alternatively activated macrophages. Relatively little is known about the factors that trigger these host responses. Chitin, a widespread environmental biopolymer of N-acetyl-beta-D-glucosamine, provides structural rigidity to fungi, crustaceans, helminths and insects. Here, we show that chitin induces the accumulation in tissue of IL-4-expressing innate immune cells, including eosinophils and basophils, when given to mice. Tissue infiltration was unaffected by the absence of Toll-like-receptor-mediated lipopolysaccharide recognition but did not occur if the injected chitin was pre-treated with the IL-4- and IL-13-inducible mammalian chitinase, AMCase, or if the chitin was injected into mice that overexpressed AMCase. Chitin mediated alternative macrophage activation in vivo and the production of leukotriene B(4), which was required for optimal immune cell recruitment. Chitin is a recognition element for tissue infiltration by innate cells implicated in allergic and helminth immunity and this process can be negatively regulated by a vertebrate chitinase.
738 citations
TL;DR: YKL-40 is found in increased quantities in the serum and lungs in a subgroup of patients with asthma, in whom expression of chitinase in both compartments correlates with the severity of asthma.
Abstract: Background The evolutionarily conserved 18-glycosyl-hydrolase family contains true chitinases and chitinase-like proteins that lack enzymatic activity. Acidic mammalian chitinase has recently been associated with animal models of asthma. The related chitinase-like protein, YKL-40 (also called human cartilage glycoprotein 39 [HCgp-39] and chitinase 3–like 1), can be readily measured in the serum. However, its relationship to asthma has not been evaluated. Methods We quantified serum YKL-40 levels in three cohorts of patients with asthma — one recruited from the patient population at Yale University, one from the University of Paris, and one from the University of Wisconsin — as well as in controls from the surrounding communities. In the Paris cohort, immunohistochemical analysis and morphometric quantitation were used to evaluate the locus of expression of YKL-40 in the lung. The clinical characteristics of the patients with high serum or lung YKL-40 levels were also evaluated. Results Serum YKL-40 levels...
525 citations
TL;DR: Some of the chitinases produced by bacterial systems that have gained worldwide research interest for their diverse properties and potential industrial uses are reviewed.
Abstract: Chitin is among the most abundant biomass present on Earth. Chitinase plays an important role in the decomposition of chitin and potentially in the utilization of chitin as a renewable resource. During the previous decade, chitinases have received increased attention because of their wide range of applications. Chito-oligomers produced by enzymatic hydrolysis of chitin have been of interest in recent years due to their broad applications in medical, agricultural, and industrial applications, including antibacterial, antifungal, hypocholesterolemic, and antihypertensive activity, and as a food quality enhancer. Microorganisms, particularly bacteria, form one of the major sources of chitinase. In this article, we have reviewed some of the chitinases produced by bacterial systems that have gained worldwide research interest for their diverse properties and potential industrial uses.
385 citations
TL;DR: Find that the human GH18 gene family is closely linked to the human major histocompatibility complex paralogon on chromosome 1, together with the recent association of GH18 chitinase activity with Th2 cell inflammation, suggests that its late expansion could be related to an emerging interface of innate and adaptive immunity during early vertebrate history.
Abstract: Chitinases (EC.3.2.1.14) hydrolyze the β-1,4-linkages in chitin, an abundant N-acetyl-β-D-glucosamine polysaccharide that is a structural component of protective biological matrices such as insect exoskeletons and fungal cell walls. The glycoside hydrolase 18 (GH18) family of chitinases is an ancient gene family widely expressed in archea, prokaryotes and eukaryotes. Mammals are not known to synthesize chitin or metabolize it as a nutrient, yet the human genome encodes eight GH18 family members. Some GH18 proteins lack an essential catalytic glutamic acid and are likely to act as lectins rather than as enzymes. This study used comparative genomic analysis to address the evolutionary history of the GH18 multiprotein family, from early eukaryotes to mammals, in an effort to understand the forces that shaped the human genome content of chitinase related proteins. Gene duplication and loss according to a birth-and-death model of evolution is a feature of the evolutionary history of the GH18 family. The current human family likely originated from ancient genes present at the time of the bilaterian expansion (approx. 550 mya). The family expanded in the chitinous protostomes C. elegans and D. melanogaster, declined in early deuterostomes as chitin synthesis disappeared, and expanded again in late deuterostomes with a significant increase in gene number after the avian/mammalian split. This comprehensive genomic study of animal GH18 proteins reveals three major phylogenetic groups in the family: chitobiases, chitinases/chitolectins, and stabilin-1 interacting chitolectins. Only the chitinase/chitolectin group is associated with expansion in late deuterostomes. Finding that the human GH18 gene family is closely linked to the human major histocompatibility complex paralogon on chromosome 1, together with the recent association of GH18 chitinase activity with Th2 cell inflammation, suggests that its late expansion could be related to an emerging interface of innate and adaptive immunity during early vertebrate history.
263 citations
TL;DR: Molecular phylogenetic analyses suggest that both active chitinases (chitotriosidase and AMCase) result from an early gene duplication event, and substantial gene specialization has occurred in time, allowing for tissue-specific expression of pH optimized chit inases and chi-lectins.
Abstract: Family 18 of glycosyl hydrolases encompasses chitinases and so-called chi-lectins lacking enzymatic activity due to amino acid substitutions in their active site. Both types of proteins widely occur in mammals although these organisms lack endogenous chitin. Their physiological function(s) as well as evolutionary relationships are still largely enigmatic. An overview of all family members is presented and their relationships are described. Molecular phylogenetic analyses suggest that both active chitinases (chitotriosidase and AMCase) result from an early gene duplication event. Further duplication events, followed by mutations leading to loss of chitinase activity, allowed evolution of the chi-lectins. The homologous genes encoding chitinase(-like) proteins are clustered in two distinct loci that display a high degree of synteny among mammals. Despite the shared chromosomal location and high homology, individual genes have evolved independently. Orthologs are more closely related than paralogues, and calculated substitution rate ratios indicate that protein-coding sequences underwent purifying selection. Substantial gene specialization has occurred in time, allowing for tissue-specific expression of pH optimized chitinases and chi-lectins. Finally, several family 18 chitinase-like proteins are present only in certain lineages of mammals, exemplifying recent evolutionary events in the chitinase protein family.
260 citations
TL;DR: This study demonstrates that Avr4 expression in Arabidopsis results in increased virulence of several fungal pathogens with exposed chitin in their cell walls, whereas the virulent of a bacterium and an oomycete remained unaltered.
Abstract: The biotrophic fungal pathogen Cladosporium fulvum (syn. Passalora fulva) is the causal agent of tomato leaf mold. The Avr4 protein belongs to a set of effectors that is secreted by C. fulvum during infection and is thought to play a role in pathogen virulence. Previous studies have shown that Avr4 binds to chitin present in fungal cell walls and that, through this binding, Avr4 can protect these cell walls against hydrolysis by plant chitinases. In this study, we demonstrate that Avr4 expression in Arabidopsis results in increased virulence of several fungal pathogens with exposed chitin in their cell walls, whereas the virulence of a bacterium and an oomycete remained unaltered. Heterologous expression of Avr4 in tomato increased the virulence of Fusarium oxysporum f. sp. lycopersici. Through tomato GeneChip analyses, we demonstrate that Avr4 expression in tomato results in the induced expression of only a few genes. Finally, we demonstrate that silencing of the Avr4 gene in C. fulvum decreases its virulence on tomato. This is the first report on the intrinsic function of a fungal avirulence protein that has a counter-defensive activity required for full virulence of the pathogen.
236 citations
TL;DR: A strategy where genetic components of the host insect can be incorporated into the fungal pathogen in order to increase host cuticle penetration ability is utilized in B. bassiana.
Abstract: Entomopathogenic fungi are currently being used for the control of several insect pests as alternatives or supplements to chemical insecticides. Improvements in virulence and speed of kill can be achieved by understanding the mechanisms of fungal pathogenesis and genetically modifying targeted genes, thus improving the commercial efficacy of these biocontrol agents. Entomopathogenic fungi, such as Beauveria bassiana, penetrate the insect cuticle utilizing a plethora of hydrolytic enzymes, including chitinases, which are important virulence factors. Two chitinases (Bbchit1 and Bbchit2) have previously been characterized in B. bassiana, neither of which possesses chitin-binding domains. Here we report the construction and characterization of several B. bassiana hybrid chitinases where the chitinase Bbchit1 was fused to chitin-binding domains derived from plant, bacterial, or insect sources. A hybrid chitinase containing the chitin-binding domain (BmChBD) from the silkworm Bombyx mori chitinase fused to Bbchit1 showed the greatest ability to bind to chitin compared to other hybrid chitinases. This hybrid chitinase gene (Bbchit1-BmChBD) was then placed under the control of a fungal constitutive promoter (gpd-Bbchit1-BmChBD) and transformed into B. bassiana. Insect bioassays showed a 23% reduction in time to death in the transformant compared to the wild-type fungus. This transformant also showed greater virulence than another construct (gpd-Bbchit1) with the same constitutive promoter but lacking the chitin-binding domain. We utilized a strategy where genetic components of the host insect can be incorporated into the fungal pathogen in order to increase host cuticle penetration ability.
190 citations
TL;DR: Bacillus cereus QQ308 produced antifungal hydrolytic enzymes, comprising chitinase, chitosanase and protease and these characteristics were unique among known strains of B. cereus.
179 citations
TL;DR: Deltatmk 1 mutants exhibited higher antifungal activity caused by low molecular weight substances, which was reflected by an over-production of 6-pentyl-alpha-pyrone and peptaibol antibiotics and a higher ability to protect bean plants against R. solani.
132 citations
TL;DR: In vivo neutralization of chitinase 3-like-1 significantly suppressed the development of dextran sulfate sodium-induced colitis by dramatically decreasing the bacterial adhesion and invasion into colonic epithelial cells.
Abstract: It has been hypothesized that dysregulated host/microbial interactions play a pivotal role in the pathogenesis of inflammatory bowel disease. However, the exact mechanisms underlying the induction and perpetuation of the intestinal disorder are unclear. Recently, we unexpectedly discovered significantly upregulated gene expression of chitinase 3-like-1 in inflamed colon of the dextran sulfate sodium-induced colitis model by employing the DNA-microarray analysis. Chitinase 3-like-1 has a chitin binding ability, but lacks the enzymatic activity of lysing microbial cell wall. Chitinase 3-like-1 protein is mainly expressed in colonic epithelial cells and macrophages in the inflamed colon of dextran sulfate sodium-induced colitis. Chitinase 3-like-1, which can be upregulated after pro-inflammatory cytokine stimulation, possesses an ability to enhance the adhesion and internalization of intracellular bacteria into colonic epithelial cells. Most importantly, in vivo neutralization of chitinase 3-like-1 significantly suppressed the development of dextran sulfate sodium-induced colitis by dramatically decreasing the bacterial adhesion and invasion into colonic epithelial cells. Furthermore, anti-chitinase 3-like-1 antibody-treated mice exhibited a significantly lower load of Salmonella typhimurium in peripheral organs as compared to control rabbit IgG-treated mice. Recently, it has been reported that acidic mammalian chitinase is expressed in the setting of T helper-2-associated inflammation and subsequently induces airway hyperresponsiveness in allergic asthma patients. In addition, pan-chitinase inhibitor significantly ameliorates T helper-2-mediated inflammation and airway hypersensitivity. These studies provide to be a novel insight into the physiological role of mammalian chitinases in host/microbial interactions, and inhibition of chitinase activity would be considered a novel therapeutic strategy of allergic and inflammatory disorders.
129 citations
TL;DR: This pilot study tested the gastric juices of 25 Italian subjects on the artificial substrates 4-methylumbelliferyl-β-D-N,N’,diacetylchitobiose or/and fluorescein isothiocyanate (FITC) to demonstrate the presence of a chitinase activity and confirmed that this activity was characteristic of AMCase.
Abstract: Chitin digestion by humans has generally been questioned or denied. Only recently chitinases have been found in several human tissues and their role has been associated with defense against parasite i
TL;DR: Results have demonstrated an induced protection of grapevine against B. cinerea by selected bacteria under field conditions, and suggest that induced resistance could be related to a stimulation of plant defense reactions in a successive manner.
Abstract: In this study, the biocontrol ability of seven grapevine-associated bacteria, previously reported as efficient against Botrytis cinerea under in vitro conditions, was evaluated in two vineyard orchards with the susceptible cv Chardonnay during four consecutive years (2002–2005) It was shown that the severity of disease on grapevine leaves and berries was reduced to different levels, depending on the bacterial strain and inoculation method Drenching the plant soil with these bacteria revealed a systemic resistance to B cinerea, even without renewal of treatment Accordingly, this resistance was associated with a stimulation of some plant defense responses such as chitinase and β-1,3-glucanase activities in both leaves and berries In leaves, chitinase activity increased before veraison (end-July) while β-1,3-glucanase reached its maximum activity at ripening (September) Reverse patterns were observed in berries, with β-1,3-glucanase peaking at full veraison (end-August) and chitinase at a later development stage Highest activities were observed with Acinetobacter lwoffii PTA-113 and Pseudomonas fluorescens PTA-CT2 in leaves, and with A lwoffii PTA-113 and Pantoea agglomerans PTA-AF1 in berries These results have demonstrated an induced protection of grapevine against B cinerea by selected bacteria under field conditions, and suggest that induced resistance could be related to a stimulation of plant defense reactions in a successive manner
TL;DR: A chitinase encoding gene from Bacillus sp.
TL;DR: Barley chitinase gene can be used to enhance fungal-resistance in crop plants such as rice, tobacco, tea and clover by exerting broad-spectrum antifungal activity.
TL;DR: The results demonstrate that the protease Ver112 and the chitinase LPCHI1 from the same fungus interacted on the egg infection and were found degrading chitinous components of eggs of the root-knot nematode Meloidogyne incognita and significantly influence its development.
Abstract: The nematophagous fungus Lecanicillium psalliotae (syn Verticillium psalliotae) is a well-known biocontrol agent In this study, a chitinase gene Lpchi1 was isolated for the first time from L psalliotae using degenerate primers and DNA-walking technique The cloned gene Lpchi1 encoding 423 amino acid residues shares a high degree of homology with other pathogenicity-related chitinases from entomopathogenic and mycoparasitic fungi The complementary DNA sequence of the mature chitinase was amplified via reverse transcription polymerase chain reaction and expressed well in Pichia pastoris GS115 Through gel filtration, the recombinant chitinase was purified as a protein of ca 45 kDa with an optimal activity at pH 70 and 376°C The purified chitinase LPCHI1 was found degrading chitinous components of eggs of the root-knot nematode Meloidogyne incognita and significantly influence its development Moreover, our results also demonstrate that the protease Ver112 and the chitinase LPCHI1 from the same fungus interacted on the egg infection
TL;DR: Western blot analysis indicated that the quantity of ChiB significantly increased when the wild-type mycelia were starved for carbon sources, a condition that induced hyphal autolysis, suggesting that chiB plays an important role in the autolytic process in A. nidulans.
Abstract: Chitinases are thought to be involved in the morphogenesis and autolysis of filamentous fungi. We cloned a gene (chiB) encoding a class V chitinase from Aspergillus nidulans. ChiB expressed in Escherichia coli had chitin-hydrolyzing activity, indicating that chiB encoded a chitinase. Deletion of chiB affected neither germination efficiency nor hyphal growth rate, but considerably reduced the intracellular and extracellular chitinase activities. The decrease in hyphal dry weight during autolytic phase was slower in the mutant than in the wild-type strain. Western blot analysis indicated that the quantity of ChiB significantly increased when the wild-type mycelia were starved for carbon sources, a condition that induced hyphal autolysis. These results suggest that chiB plays an important role in the autolytic process in A. nidulans.
TL;DR: It is demonstrated for the first time that a chitin-like material is present in A. aegypti eggs, ovaries and eggshells, and a Chitin synthesis inhibitor can be used to inhibit mosquito oogenesis, and chitIn synthesis inhibitors have potential for controlling mosquito populations.
TL;DR: Findings indicate that GlcNAc-GlcN is produced from chitin by the cooperative hydrolytic reactions of both Pa-Chi and Pa-COD.
Abstract: A chitin-degrading bacterial strain, KN1699, isolated from Yatsu dry beach (Narashino, Chiba Prefecture, Japan), was identified as Vibrio parahaemolyticus. Treatment of powdered chitin with crude enzyme solution prepared from the supernatant of KN1699 cultures yielded a disaccharide, β-d-N-acetylglucosaminyl-(1,4)-d-glucosamine (GlcNAc-GlcN), as the primary chitin degradation product. The extracellular enzymes involved in the production of this heterodisaccharide, chitinase (Pa-Chi; molecular mass, 92 kDa) and chitin oligosaccharide deacetylase (Pa-COD; molecular mass, 46 kDa), were isolated from the crude enzyme solution, and their hydrolysis specificities were elucidated. These studies confirmed that (1) Pa-Chi hydrolyzes chitin to produce (GlcNAc)2 and (2) Pa-COD hydrolyzes the acetamide group of reducing end GlcNAc residue of (GlcNAc)2. These findings indicate that GlcNAc-GlcN is produced from chitin by the cooperative hydrolytic reactions of both Pa-Chi and Pa-COD.
TL;DR: Two strains of Trichoderma harzianum used for biological control of fungal plant pathogens were investigated for the production of serine protease, chitinase and antibiotic activity in relation to entomopathogenicity, suggesting that the virulence factors involved in biocontrol are the same as those for insect pathogenicity.
TL;DR: To evaluate the biocontrol efficacy of culture filtrate containing chitinase from Trichoderma harzianum against Heliothis.
Abstract: Aims: To evaluate the biocontrol efficacy of culture filtrate containing chitinase from Trichoderma harzianum against Heliothis.
Methods and Results: T. harzianum was cultured by submerged fermentation using colloidal chitin as sole carbon source. The ability of the culture filtrate to hydrolyse colloidal chitin indicated the presence of chitinase as one of its components. Biocontrol assay on Heliothis showed that the culture filtrate is a potent antifeedant as it reduced the feeding rate and body weight of the larvae. It reduced the successful pupation and increased larval and pupal mortality in a dosage-dependent manner when applied topically. The highest mortalities (70%) were recorded for groups treated with 2000 U ml−1 chitinase activity. The percentage of adult emergence was zero for the highest chitinase concentration (2000 U ml−1) tried.
Conclusions: The studies showed that the culture filtrate containing chitinase from T. harzianum is capable of negatively affecting the growth and metamorphosis of Heliothis larvae.
Significance and Impact of the Study: In view of the need for safer and environmentally friendly pest management tools, the present study could help in the development of enzyme-based biopesticides against Heliothis.
01 Jan 2007
TL;DR: Four hundred bacterial isolates were isolated from rhizosphere of some plants collected from Egypt and screened for production of chitinase enzyme and only four isolates designated MS1, MS2, MS3 and MS4 were the most potent chitinolytic bacterial species.
Abstract: Four hundred bacterial isolates were isolated from rhizosphere of some plants collected from Egypt and screened for production of chitinase enzyme Only four isolates designated MS1, MS2, MS3 and MS4 were the most potent chitinolytic bacterial species SDS-PAGE analysis of vegetative and sporulated cells of the four isolates revealed that the protein profile of the four isolates were different from each other in their banding pattern and were identified as Bacillus licheniformis, Stenotrophomonas maltophilia, Bacillus licheniformis and B thuringiensis In vitro MS1 and MS3 were the most active species, so they suppressed the growth of all tested pathogenic fungi (Rhizoctonia solani, Macrophomina phasiolina, Fusarium culmorum, Pythium sp, Alternaria alternata and Sclerotium rolfsii) Also, MS3 produced the highest level of chitinase enzyme (127 µ/ml) after 4 days incubation as compared with the other isolates In green-house experiment, B licheniformis (MS3) significantly reduced the damping off disease caused by Rhizoctonia solani, in Helianthus annus using the seed coat or soil draing treatments
TL;DR: Crystal structures of ScCTS1 in complex with inhibitors from three series reveal striking mimicry of carbohydrate substrate by small aromatic moieties and a pocket that could be further exploited in optimization of these inhibitors.
TL;DR: Wheat chitinase gene from wheat has been subcloned and overexpressed in Escherichia coli BL-21 (DE3) and molecular phylogeny analyses indicated that it belongs to an acidic form of class VII chit inase (glycosyl hydrolase family 19) and shows 77% identity with other wheat ch itinase of class IV and low level identity to other plant chitInase.
TL;DR: Optimization of physico-chemical parameters, nutritional parameters and studies on the degradation of colloidal chitin to N-acetyl-D-glucosamine showed improved efficiency when endochitinase and chitobiase were used in combination.
TL;DR: Symptoms of infection by P. grisea in rice seedlings were evident after 14 days evaluation date, but according to the standard scale proposed by the International Rice Research Institute, these symptoms fell into the resistance category of blast diseases.
TL;DR: It is confirmed that multiple mechanisms are involved in suppressing phytopathogens as evidenced by the involvement of chitinase and beta-1,3-glucanase in inhibition of R. solani but not P. capsici by isolate GRC3.
Abstract: A study was conducted to investigate the possibility of involvement of chitinase and β-1,3-glucanase of an antagonistic fluorescent Pseudomonas in growth suppression of phytopathogenic fungi, Phyto...
Journal Article•
TL;DR: It was found that the Crchi1 expression was suppressed by glucose but strongly stimulated by chitin or solubilized components of the cell wall from Rhizoctonia solani, suggesting that these chit inases have probably evolved from a common ancestor.
Abstract: Clonostachys rosea (syn. Gliocladium roseum) is a well-known biocontrol agent and widely distributed around the world. In this study, an endochitinase gene Crchi1 was isolated from the mycoparasitic fungus C. rosea using the DNA walking strategy. The Crchi1 ORF is 1,746 bp long and interrupted by three introns. The cloned gene Crchi1 encodes 426 amino acid residues and shares a high degree of similarity with other chitinases from entomopathogenic and mycoparasitic fungi. Several putative binding sites for transcriptional regulation of Crchi1 in response to carbon (5'-SYGGRG-3') and nitrogen (5'-GATA-3') were identified in the upstream of Crchi1. Expression of Crchi1 gene in different carbon sources was analyzed using real-time PCR (RT-PCR). We found that the Crchi1 expression was suppressed by glucose but strongly stimulated by chitin or solubilized components of the cell wall from Rhizoctonia solani. Phylogenetic analysis of chitinases from entomopathogenic and mycoparasitic fungi suggests that these chitinases have probably evolved from a common ancestor.
TL;DR: These findings indicate the ability of modern poultry to digest chitin but suggest that the ingestion of insects is not an important source of nutrients, at least from the exoskeleton.
Abstract: 1. Little is known about the ability of farmed poultry to digest chitin and derive nutrients from the ingestion of insects. 2. Commercial chitin derived from crustacean shell waste was found to contain 373 g crude protein, 265 g ash, 23·5 g ether extract, 130 g calcium and 16·4 g phosphorus per kg, on an air-dry basis. 3. It was included in diets at 0, 25, 50 and 75 g chitin per kg and fed to 320 1-d-old broiler males, over a 21-d period. There were no statistically significant treatment effects on weight gain or feed efficiency. Apparent digestibility of chitin protein was 0·48, 0·50 and 0·45, at the 25, 50 and 75 g per kg inclusions, respectively. Mean AME and AMEN values of chitin were determined as 8·97 and 8·86 MJ/kg. 4. In a subsequent study, mean TME and TMEN values of chitin were determined to be 8·23 and 8·21 MJ per kg, respectively. Addition of chitinase to the diet increased TME and TMEN of chitin to 8·81 and 8·79 MJ per kg, respectively (P < 0·05). True digestibility of chitin protein was dete...
TL;DR: P pH regulation is mediated by the transcriptional factor Pac1 (homologous to PacC regulator in other fungi), encoded by pac1 whose expression increases with pH, which modulates T. harzianum antifungal activity since wild type and mutants inhibit several phytopathogenic fungal strains at various degrees in different assays.
TL;DR: Moderately resistant rice cultivars had higher levels of chitinase activity and lower disease severity and numbers of infection cushions formed compared to IR58, while susceptible cvs Betichikon, Dudruchi, Khatochalani, Padi Pulut Malat, Kakua, IR72, Khakibinni had higher Levels ofChitinases were induced following Rhizoctoniasolani infection.
Abstract: Various rice cultivars were selected and screened for their reaction to sheath blight in the greenhouse. Cluster analysis of percent relative lesion height (% RLH) generated four groups of cultivars with a coefficient of similarity of 3.27. Chitinase activities were detected 24 h after inoculation of moderately resistant cvs Betichikon, Dudruchi, Khatochalani, Padi Pulut Malat, Kakua, IR72, Khakibinni. But in the susceptible cv. IR58, chitinase activity was detected only 36 h after inoculation. Western blot analysis showed that class 1 and class 2 chitinases were induced following Rhizoctoniasolani infection of these cultivars. The % RLH and the number of infection cushions were negatively correlated with the level of chitinase activity. Moderately resistant rice cultivars had higher levels of chitinase activity and lower disease severity and numbers of infection cushions formed compared to IR58.