Induction Of Chitinase Activity Research Articles

The Characteristics of Chitinase Expression in Aeromonas schubertii

In this study, chitinase activity in an incubation broth of Aeromonas schubertii was measured using colloidal chitin azure as the substrate. More specifically, the induction of chitinases due to amendment with various carbon sources was examined. The highest chitinase activity was found following amendment with 0.5-1.0 % chitin powder, whereas the activity increased negligibly due to amendment with other carbon sources, such as glucose, GlcNAc, GlcN, sorbitol, sucrose, cellulose, or starch. The chitinase activity induced by the chitin powder was suppressed when the glucose, GlcNAc, GlcN, or starch was added simultaneously to the medium but was not suppressed by the addition of sorbitol, sucrose, or cellulose. The activity of chitinase in the crude extract was also not directly inhibited by glucose. Taken together, these findings suggest that the induction of chitinase activity depends on the acquisition of suitable carbon sources from the environment and that induction occurs at a regulatory level.

Induction of chitinase activity by exogenous cytokinins in excised dark-grown cucumber cotyledons: involvement of Ca 2+ and staurosporine-sensitive protein kinase(s) in cytokinin signaling

Cotyledons were excised from 7-day-old dark-grown cucumber seedlings and treated with water, benzyladenine (BA), kinetin (K), zeatin (Z), or zeatin riboside (ZR) in dark after endogenous cytokinin depletion. We have compared changes in chitinase (EC. 3.2.1.14) activity induced by these cytokinins. We find that the activities of chitinase and its isoforms increase by approximately 3- to 6-fold following BA, Z, and ZR treatments. Among these treatments, Z was more effective. K was totally ineffective in inducing chitinase activity. Immunoblot analysis suggests that the cytokinin Z-induction of enzyme activity is due to the induction of higher chitinase protein levels and not the activation of existing enzyme. Furthermore, the Z-induced chitinase activity and its protein accumulation were completely inhibited by the protein kinase inhibitor staurosporine, whereas the protein phosphatase inhibitor sodium fluoride was not effective in such inhibitions. Treatment of cotyledons with extemal $CaCl_2$ and calcium ionophore increased the basal chitinase activity by 6- and 5-fold, respectively. Moreover, the effects of staurosporine, sodium fluoride, and $Ca^{2+}$ on Z-induced chitinase activity correlate with their effects on chitinase protein levels. Taken together, our data suggests $Ca^{2+}$ and staurosporine-sensitive protein kinase(s) as components of the cytokinin transduction machinery involving induction of chitinase in cucumber.

Differential induction of chitinase activity in flax (Linum usitatissimum) in response to inoculation with virulent or avirulent strains of Melampsora lini, the cause of flax rust

Chitinase enzymes are induced in many plants in response to pathogen challenge and other stress stimuli. Chitinase induction in flax leaves in response to inoculation with flax rust, caused by Melampsora lini (Pers.) Lev., was investigated in a line of flax (Forge) that has four resistance genes, viz. L6, M, N and P2. Four avirulent rust strains, each of which interacts with just one of the resistance genes in Forge, as well as a strain that is virulent on Forge, were used. Thus chitinase levels associated with resistance reactions triggered by the L6, M, N or P2 genes, and by a susceptible reaction, have been compared in the same host genotype. A marked increase in chitinase activity in inoculated leaves was observed with all four resistance reactions, with the increase occurring earlier with the P2 resistance reaction compared with the L6, M, and N reactions. A moderate increase in chitinase activity was also observed in systemic (new-growth) leaves of flax plants inoculated with strains interacting with the M, N or P2 genes. Leaves inoculated with a virulent strain of rust also had increased chitinase activity but the increase was much less than that found in leaves inoculated with the avirulent strains.

Ethylene responsiveness of soybean cultivars characterized by leaf senescence, chitinase induction and nodulation

Summary A total of 161 cultivars of soybean (Glycine max L. Mere.) were tested for their responsiveness to ethyl­ ene treatments, using senescence of the primary leaves and the induction of chitinase activity in the roots as response markers. Cultivar «Gong jiao 6308-1» showed rapid chlorosis and the highest chitinase induc­ tion upon treatments with ethylene. The inducibility of chitinase by ethylene increased with increasing age of the plant. In addition, it was found that upon repeated ethylene treatments nodule formation of culti­ var «Gong jiao 6308-1» was completely blocked in the lower part of the root system when inoculated with Bradyrhizobium japonicum. In several other cultivars, e.g. in «Bai tie jia qing», ethylene treatments did not induce leaf senescence or induction of chitinase activity. Cultivar «Bai tie jia qing» also showed completely normal nodulation even after repeated ethylene treatments. These results demonstrate that different soy­ bean cultivars show a wide variation and strongly differ in their ethylene responsiveness.

Role of salicylic acid and intracellular Ca 2+ in the induction of chitinase activity in carrot suspension culture

Treatment of carrot suspension culture with a fungal cell wall preparation induced the production of chitinase. This treatment also caused an accumulation of salicylic acid both in the cells and in the extracellular medium. Culture medium of induced cells, which contained elevated levels of salicylic acid, was able to induce chitinase activity in a non-induced suspension culture. Exogenous supply of authentic salicylic acid induced chitinase activity in carrot cells more rapidly than the fungal cell wall. Removal of extracellular Ca2+ by treatment with the calcium chelator, EGTA [ethylene glycol bis(β-aminoethyl ether) N,N′-tetraacetic acid], abolished the elicitormediated production of both salicylic acid and chitinase. Verapamil caused similar effects, whereas the addition of the Ca2+ ionophore A23187, enhanced these cellular responses in the absence of elicitor. These observations suggest that Ca2+ plays an important role in the induced production of chitinase and salicylic acid.

Are ethylene and 1-aminocyclopropane-1-carboxylic acid involved in the induction of chitinase and ?-1,3-glucanase activity in sunflower cell-suspension cultures?

Auxin-dependent, heterotrophic suspension cells of sunflower (Helianthus annuus L. C.K. Spanners All-zweck) showed, on a cell-protein basis, a seven-fold increase in chitinase activity, which began 5 d after treatment with 10−5 mol·L−1 of the triazole-type growth retardant BAS 111.W. In proportion to this increase, chitinase activity appeared to be excreted into the culture medium. The intracellular activity of β-1,3-glucanase, assayed fluorimetrically with laminarin as the substrate, was only slightly enhanced. Dose-response experiments with BAS 111.W showed that the onset of the induction of chitinase activity coincided with an inhibition of ethylene formation and an accumulation of endogenous 1-aminocyclopropane-1-carboxylic acid (ACC) as a result of blocking the conversion of ACC to ethylene. Other nitrogen-heterocyclic growth retardants (e.g. tetcyclacis, ancymidol), the triazole-type fungicide BAS 480.F, salicylic acid, CoCl2 and 2,4-dichlorophenoxy-acetic acid, which also increased the ACC/ethylene ratio, similarly induced chitinase activity. In contrast, aminoethoxy vinylglycine, which simultaneously lowered endogenous ACC and ethylene formation, did not stimulate chitinase activity. However, after addition of BAS 111.W and ACC, an accumulation of endogenous ACC was accompanied by a strong induction of the enzymatic activity. This effect did not correlate with changes in the cell culture growth nor in the cellular contents of immunoreactive abscisic acid, 3-indoleacetic acid, gibberellins or cytokinins. Furthermore, ethephon, which chemically generates ethylene, led to a slight reduction in ACC levels and tended to decrease chitinase activity relative to the control. In conclusion, it is hypothesized that the induction of chitinase activity in sunflower cell suspensions is antagonistically regulated by ethylene and ACC. At least at higher production rates, ethylene appears to function as an inhibiting factor whereas ACC may be a promoting one. The stimulation of chitinase and β-1,3-glucanase activity, caused by the retardant BAS 111.W and the fungicide BAS 480.F, is discussed as an additional effect of both compounds which possibly leads to an increased resistance of plants to fungal infections.