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Applied and Environmental Microbiology, May 1999, p. 1858-1863, Vol. 65, No. 5
Abteilung für Mikrobielle Biochemie,
Institut für Biochemische Technologie und Mikrobiologie, TU
Wien, A-1060 Vienna, Austria,1 and
Dipartimento di Arboricoltura, Botanica e Patologia
Vegetale, Sezione di Patologia Vegetale, Universita degli Studi di
Napoli "Federico II," and Centro di Studio CNR per le Tecniche
di Lotta Biologica, 80050 Portici, Italy2
Received 23 November 1998/Accepted 2 March 1999
Regulation of the expression of the two major chitinase genes,
ech42 (encoding the CHIT42 endochitinase) and
nag1 (encoding the CHIT73
N-acetyl-
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Expression of Two Major Chitinase Genes of Trichoderma
atroviride (T. harzianum P1) Is Triggered by Different
Regulatory Signals
-D-glucosaminidase), of the
chitinolytic system of the mycoparasitic biocontrol fungus
Trichoderma atroviride (= Trichoderma harzianum
P1) was investigated by using a reporter system based on the
Aspergillus niger glucose oxidase. Strains harboring
fusions of the ech42 or nag1 5'
upstream noncoding sequences with the A. niger goxA
gene displayed a glucose oxidase activity pattern that was consistent
under various conditions with expression of the native
ech42 and nag1 genes, as assayed by Northern
analysis. The expression product of goxA in the mutants was
completely secreted into the medium, detectable on Western blots, and
quantifiable by enzyme-linked immunosorbent assay. nag1
gene expression was triggered during growth on fungal (Botrytis
cinerea) cell walls and on the chitin degradation product
N-acetylglucosamine. N-Acetylglucosamine, di-N-acetylchitobiose, or
tri-N-acetylchitotriose also induced nag1 gene
expression when added to mycelia pregrown on different carbon sources.
ech42 expression was also observed during growth on fungal
cell walls but, in contrast, was not triggered by addition of
chitooligomers to pregrown mycelia. Significant ech42
expression was observed after prolonged carbon starvation, independent
of the use of glucose or glycerol as a carbon source, suggesting that
relief of carbon catabolite repression was not involved in induction
during starvation. In addition, ech42 gene transcription was triggered by physiological stress, such as low temperature, high
osmotic pressure, or the addition of ethanol. Four copies of a putative
stress response element (CCCCT) were found in the ech42 promoter.
*
Corresponding author. Mailing address: Abteilung
für Mikrobielle Biochemie, Institut für Biochemische
Technologie und Mikrobiologie, TU Wien, Getreidemarkt 9-172.5, A-1060 Vienna, Austria. Phone: 43-1 58801 17251. Fax: 43-1 581 62 66. E-mail: rmach{at}mail.zserv.tuwien.ac.at.
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