Chitinase

About: Chitinase is a research topic. Over the lifetime, 4690 publications have been published within this topic receiving 161786 citations. The topic is also known as: 1,4-beta-poly-N-acetylglucosaminidase & poly-beta-glucosaminidase.

Signal Transduction by Tga3, a Novel G Protein α Subunit of Trichoderma atroviride

Abstract: Several fungi belonging to the genus Trichoderma can act as mycoparasites and are used commercially as biological control agents against plant-pathogenic fungi, such as Rhizoctonia solani, Botrytis cinerea, Sclerotium rolfsii, Sclerotinia sclerotiorum, and Pythium spp (5, 6, 18) Mycoparasitic strains can penetrate and kill the host fungi Mycoparasitism is accompanied by the secretion of antifungal metabolites, such as peptaibol antibiotics (32, 47), and morphological changes, such as coiling around the host and development of hooks and/or appressorium-like structures (11) Hydrolytic enzymes, such as chitinases, glucanases, and proteases, also are important for biocontrol activity, since they enable Trichoderma to degrade the host's cell wall and to utilize its cellular contents (20) Chitinase gene expression is induced by colloidal chitin, fungal cell walls, or the chitin monomer N-acetylglucosamine (29) In Trichoderma atroviride the N-acetylglucosaminidase (NAGase)-encoding gene, nag1, has a major impact on the induction by chitin of other chitinases (4) In mycoparasitic interactions between T atroviride and R solani, expression of ech42, which encodes endochitinase 42, is triggered by a low-molecular-weight diffusible factor released from the host prior to physical contact between the two fungi (10, 50) Lectins in the host's cell wall can induce coiling of the mycoparasite around the host (1, 24, 41) Elucidation of the signaling pathways underlying mycoparasitism has only recently begun Heterotrimeric G proteins are composed of α, β, and γ subunits Gα subunits play pivotal roles in the recognition process, virulence, and virulence-dependent development in a number of plant-pathogenic fungi (3, 15, 26, 27, 31) Fungal Gα subunits are highly conserved and can be divided into three major subgroups (3) In T atroviride, the subgroup I Gα protein Tga1 affects light-induced conidiation and mycoparasitism-related coiling (41) The corresponding protein in Trichoderma virens is involved in antagonism against S rolfsii but not in antagonism against R solani ΔtgaA loss-of-function mutants sporulate and have coiling behavior similar to that of the wild type (37), suggesting that the subgroup I Gα subunits have different functions in these mycoparasites The T virens subgroup II G protein α subunit, TgaB, has no specific role in development or mycoparasitism (37) Fungal subgroup III Gα proteins also regulate morphological and developmental processes, such as germination, conidiation, and secondary metabolite production (28, 53), and they may increase intracellular cyclic AMP (cAMP) levels by stimulating adenylyl cyclase (28, 33, 39) The objectives of this study were to isolate a subgroup III Gα subunit deletion mutant of T atroviride and to determine its role in development and mycoparasitism This report is the first report of the role of the Tga3-mediated G protein pathway in mycoparasitism-related properties, such as host recognition, chitinase expression, and secretion

What are the roles of chitinases in the growing fungus

Abstract: Filamentous fungi with chitin as a major component of their cell walls produce chitinases at all stages of active growth, i.e. during spore germination, exponential growth and mycelial development. The roles of chitinases in these processes have been investigated by assessing the effects of treatment with the inhibitor, allosamidin. Inhibition has only been observed, however, of spore germination, of cell separation in budding yeasts and of the action of a yeast toxin, and not of apical extension or branching. This may be explained by the finding that chitinase activities in situ have different properties to those in cell homogenates, and appear to be protected from environmental stresses.

Purification and characterization of a thermophilic and acidophilic chitinase from Microbispora sp. V2.

Abstract: Aim: Purification and characterization of a chitinase from Microbispora sp. V2. Methods and Results: The chitinase from Microbispora sp. V2 was purified to homogeneity by gel filtration chromatography with 4·6% recovery. It had a molecular weight of 35 kDa and showed maximum activity towards p-nitrophenyl-β-d-N,N′-diacetylchitobiose, indicating a chitobiosidase activity. The enzyme had a pH optimum of 3·0 and temperature optimum of 60 °C. It was stable in a wide pH range from 3·0 to 11·0, retaining 61% activity at pH 3·0 and 52% activity at pH 11·0. It retained 71% activity at 30 °C and 45% activity at 50 °C, up to 24 h. The enzyme activity was not inhibited by any of the metal ions tested except Hg2+, in the presence of which only 10% activity was retained. Conclusions: The 35 kDa chitinase from Microbispora sp. V2 has an acidic pH optimum and a high temperature optimum. It is fairly stable and active, and degrades chitin efficiently, although the growth of the culture and enzyme production is slow. Significance and Impact of the Study: This report is the first detailed study of a chitinase from Microbispora sp. V2, isolated from hot springs. The chitinase from Microbispora sp. V2 may have potential applications in the recycling of chitinous wastes, particularly due to its thermophilic and acidophilic character. Studies at molecular level may provide further insight on the chitinolytic system of Microbispora spp. with respect to the number and types of chitinases and their regulation.

Differential induction of apoplastic peroxidase and chitinase activities in susceptible and resistant wheat cultivars by Russian wheat aphid infestation

Abstract: The intercellular peroxidase and chitinase activities of three wheat cultivars [Triticum aestivum L. cvs `Tugela DN', `Molopo DN' (Gariep) and `Betta DN'] containing the Dn-1 gene for resistance to the Russian wheat aphid (RWA) Diuraphis noxia (Mordvilko) and the corresponding near-isogenic susceptible cultivars (`Tugela', `Molopo' and `Betta') were studied under conditions of infestation and non-infestation. The aim was to gain information on the mechanism of resistance. The resistance response was induced by RWA infestation. Infestation rapidly induced the activities of both enzymes selectively in resistant wheat to levels of magnitudes higher than those in susceptible wheat. The genetic background in which the Dn-1 resistance gene is bred played a role and the level of activity corresponded to the level of resistance. Immunologic studies confirmed that the induction of enzyme activities was due to the induction of higher protein levels. These results indicate that peroxidase and chitinase may have a role in insect resistance.

Activation of a Bean Chitinase Promoter in Transgenic Tobacco Plants by Phytopathogenic Fungi.

Abstract: The temporal and spatial expression of a bean chitinase promoter has been investigated in response to fungal attack. Analysis of transgenic tobacco plants containing a chimeric gene composed of a 1.7-kilobase fragment carrying the chitinase 5B gene promoter fused to the coding region of the gus A gene indicated that the chitinase promoter is activated during attack by the fungal pathogens Botrytis cinerea, Rhizoctonia solani, and Sclerotium rolfsii. Although induction of [beta]-glucuronidase activity was observed in tissues that had not been exposed to these phytopathogens, the greatest induction occurred in and around the site of fungal infection. The increase in [beta]-glucuronidase activity closely paralleled the increase in endogenous tobacco chitinase activity produced in response to fungal infection. Thus, the chitinase 5B-gus A fusion gene may be used to analyze the cellular and molecular details of the activation of the host defense system during pathogen attack.