Topic
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.
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TL;DR: The extracellular washing fluid from leaves of transgenic plants expressing either of the secreted class I enzymes exhibited antifungal activity on F. solani germlings in vitro comparable to that of the purified vacuolar class I proteins.
Abstract: Different isoforms of chitinases and [beta]-1,3-glucanases of tobacco (Nicotiana tabacum cv Samsun NN) were tested for their antifungal activities The class I, vacuolar chitinase and [beta]-1,3-glucanase isoforms were the most active against Fusarium solani germlings, resulting in lysis of the hyphal tips and in growth inhibition In additon, we observed that the class I chitinase and [beta]-1,3-glucanase acted synergistically The class II isoforms of the two hydrolases exhibited no antifungal activity However, the class II chitinases showed limited growth inhibitory activity in combination with higher amounts of class I [beta]-1,3-glucanase The class II [beta]-1,3-glucanases showed no inhibitory activity in any combination In transgenic tobacco plants producing modified forms of either a class I chitinase or a class I [beta]-1,3-glucanase, or both, these proteins were targeted extracellularly Both modified proteins lack their C-terminal propeptide, which functions as a vacuolar targeting signal Extracellular targeting had no effect on the specific activities of the chitinase and [beta]-1,3-glucanase enzymes Furthermore, the extracellular washing fluid (EF) from leaves of transgenic plants expressing either of the secreted class I enzymes exhibited antifungal activity on F solani germlings in vitro comparable to that of the purified vacuolar class I proteins Mixing EF fractions from these plants revealed synergism in inhibitory activity against F solani; the mixed fractions exhibited inhibitory activity similar to that of EF from plants expressing both secreted enzymes
437 citations
TL;DR: A model is proposed in which the vacuole-localized chitinase and [beta]-1,3-glucanase are used as a last line of defense to be released when the attacked host cells lyse, which would be involved in recognition processes, releasing defense activating signaling molecules from the walls of invading pathogens.
Abstract: Plants respond to an attack by potentially pathogenic organisms and to the plant stress hormone ethylene with an increased synthesis of hydrolases such as chitinase and [beta]-1,3-glucanase. We have studied the subcellular localization of these two enzymes in ethylene-treated bean leaves by immunogold cytochemistry and by biochemical fractionation techniques. Our micrographs indicate that chitinase and [beta]-1,3-glucanase accumulate in the vacuole of ethylene-treated leaf cells. Within the vacuole label was found predominantly over ethylene-induced electron dense protein aggregates. A second, minor site of accumulation of [beta]-1,3-glucanase was the cell wall, where label was present nearly exclusively over the middle lamella surrounding intercellular air spaces. Both kinds of antibodies labeled Golgi cisternae of ethylene-treated tissue, suggesting that the newly synthesized chitinase and [beta]-1,3-glucanase are processed in the Golgi apparatus. Biochemical fractionation studies confirmed the accumulation in high concentrations of both chitinase and [beta]-1,3-glucanase in isolated vacuoles, and demonstrated that only [beta]-1,3-glucanase, but not chitinase, was present in intercellular washing fluids collected from ethylene-treated leaves. Based on these results and earlier studies, we propose a model in which the vacuole-localized chitinase and [beta]-1,3-glucanase are used as a last line of defense to be released when the attacked host cells lyse. The cell wall-localized [beta]-1,3-glucanase, on the other hand, would be involved in recognition processes, releasing defense activating signaling molecules from the walls of invading pathogens.
427 citations
TL;DR: The understanding of biochemistry and genetics of chitinolytic enzymes, their phylogenetic relationships and methods of estimation will make them more useful in a variety of processes in near future.
414 citations
TL;DR: Two endochitinases (EC 3.2.1.14) of M(r) values of approximately 34,000 and approximately 32,000 have been purified from cultured tissues of Nicotiana tabacum cv, indicating that chitinase accumulation is controlled, at least in part, at the mRNA level.
Abstract: Two endochitinases (EC 3.2.1.14) of Mr values of ≈34,000 and ≈32,000 have been purified from cultured tissues of Nicotiana tabacum cv. Havana 425. The chitinase content of cloned tobacco pith tissues subcultured on hormone-free medium increases by ≈5-fold to 8% of the soluble protein over a 7-day period. This induction is inhibited >90% by addition of combinations of the plant hormones auxin and cytokinin to the culture medium. Chitinase is also developmentally regulated in the intact plant. Not detectable in leaves near the top of the plant, it is 1-4% of the soluble protein in roots and lower leaves. A cDNA clone of tobacco chitinase was isolated containing a single, large open reading frame of 310 amino acids that includes the complete amino acid sequence of the mature enzyme. Chitinase and chitinase mRNA measured by RNA blot analysis show similar patterns of regulation indicating that chitinase accumulation is controlled, at least in part, at the mRNA level. The patterns were also similar to those obtained with glucan endo-1,3-β-glucosidase (EC 3.2.1.39) suggesting that the two enzymes are coordinately regulated.
397 citations
TL;DR: In situ fluorescence studies showed that Avr4 also binds to cell walls of C. fulvum during infection of tomato, where it most likely protects the fungus against tomato chitinases, suggesting that AvR4 is a counter-defensive virulence factor.
Abstract: Resistance against the leaf mold fungus Cladosporium fulvum is mediated by the tomato Cf proteins which belong to the class of receptor-like proteins and indirectly recognize extracellular avirulence proteins (Avrs) of the fungus. Apart from triggering disease resistance, Avrs are believed to play a role in pathogenicity or virulence of C. fulvum. Here, we report on the avirulence protein Avr4, which is a chitin-binding lectin containing an invertebrate chitin-binding domain (CBM14). This domain is found in many eukaryotes, but has not yet been described in fungal or plant genomes. We found that interaction of Avr4 with chitin is specific, because it does not interact with other cell wall polysaccharides. Avr4 binds to chitin oligomers with a minimal length of three N-acetyl glucosamine residues. In vitro, Avr4 protects chitin against hydrolysis by plant chitinases. Avr4 also binds to chitin in cell walls of the fungi Trichoderma viride and Fusarium solani f. sp. phaseoli and protects these fungi against normally deleterious concentrations of plant chitinases. In situ fluorescence studies showed that Avr4 also binds to cell walls of C. fulvum during infection of tomato, where it most likely protects the fungus against tomato chitinases, suggesting that Avr4 is a counter-defensive virulence factor.
392 citations