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Applied and Environmental Microbiology, December 2001, p. 5643-5647, Vol. 67, No. 12
Cornell University, Department of
Horticultural Sciences, Geneva, New York 14456
Received 15 March 2001/Accepted 24 September 2001
Chitinolytic and glucanolytic fungal cell wall-degrading enzymes
have been suggested to be primary determinants of biocontrol by
Trichoderma spp. We examined the effects of ammonium,
glucose, chitin, and chito-oligomers on transcription of specific genes and secretion of fungal cell wall-degrading enzymes. The genes ech42, nag1, and
gluc78 were examined, as were the enzymes they encode
(endochitinase CHIT42, N-acetylhexosaminidase CHIT73,
and glucan exo-1,3-
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.12.5643-5647.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Interaction of Ammonium, Glucose, and Chitin
Regulates the Expression of Cell Wall-Degrading Enzymes in
Trichoderma atroviride Strain P1
-glucanase GLUC78, respectively).
gluc78 could be induced by nitrogen starvation alone,
while both ech42 and nag1 required
nitrogen starvation and the presence of chitin for induction.
Starvation for both ammonium and glucose resulted in very early
expression and secretion of all cell wall-degrading enzymes examined.
In the presence of low levels of ammonium (10 mM), both chito-oligomers
and chitin triggered CHIT42 and CHIT40 (chitobiosidase) production.
CHIT73 secretion occurred in the presence of
N-acetylglucosamine and chito-oligomers, while chitin was less effective. The presence of different chito-oligomers resulted
in secretion of specific N-acetylhexosaminidases, of which CHIT73 is one. Our results indicate that the expression and
secretion of cell wall-degrading enzymes is nitrogen repressed, that
effects of carbon and nitrogen nutrition are interactive, and that
especially for chitinolytic enzymes, the inductive effect of chitin is
altered by the level of ammonium or glucose in the medium.
*
Corresponding author. Mailing address: Department of
Horticultural Sciences, Cornell University, Geneva, NY 14456-0462. Phone: (315) 787-2246. Fax: (315) 787-2320. E-mail:
bdd1{at}cornell.edu.
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