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Antifungal activity of sugar beet chitinase against Cercospora beticola : an autoradiographic study on cell wall degradation
Author(s) -
NIELSEN K. K.,
JØRGENSEN P.,
MIKKELSEN J. D.
Publication year - 1994
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/j.1365-3059.1994.tb01647.x
Subject(s) - chitinase , chitin , sugar beet , biology , cell wall , hypha , spore germination , cercospora , biochemistry , lysis , coccidioides immitis , spore , hydrolysis , microbiology and biotechnology , leaf spot , botany , enzyme , horticulture , chitosan
Two independent bioassays demonstrated an antifungal effect of a basic sugar beet chitinase on Cercospora beticola , the causal agent of leaf spot disease in sugar beet ( Beta vulgaris ). In one assay, the growth of submerged spore cultures of C. beticola in microtitre wells was followed by measuring the increase in absorbance at 620 nm. Addition of chitinase to the culture resulted in a delay in germination and a slower initial growth rate. A more detailed picture of the action of the chitinase on the fungal cell wall was provided by an autoradiographic study. An intense labelling was observed at the apex of fungal hyphae grown in medium containing [ 3 H] N ‐acetylglucosamine, through incorporation of the radioactive chitin monomer into newly synthesized chitin in the cell wall. After fixation of the fungal specimen, the radioactive labelling could be removed by treatment with purified chitinase, i.e. nascent chitin chains were hydrolysed by the enzyme. When the fungal culture was subjected to a chase phase prior to fixation, the radioactive depositions were less accessible to hydrolysis by the chitinase. HPLC analysis of the radioactive hydrolysis products released from the apex of the fungal hyphae showed that the main products were small chito‐oligosaccharides, mainly dimers, trimers and tetramers of chitin.