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Eukaryotic Cell, March 2009, p. 410-420, Vol. 8, No. 3
1535-9778/09/$08.00+0 doi:10.1128/EC.00256-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
The G-Alpha Protein GNA3 of Hypocrea jecorina (Anamorph Trichoderma reesei) Regulates Cellulase Gene Expression in the Presence of Light
,
Monika Schmoll,*
André Schuster,
Roberto do Nascimento Silva,
and
Christian P. Kubicek
Research Area Gene Technology and Applied Biochemistry, Institute for Chemical Engineering, Vienna University of Technology, Getreidemarkt 9/1665, Vienna 1060, Austria
Received 30 July 2008/ Accepted 30 December 2008
Although the enzymes enabling Hypocrea jecorina (anamorph Trichoderma reesei) to degrade the insoluble substrate cellulose have been investigated in some detail, little is still known about the mechanism by which cellulose signals its presence to the fungus. In order to investigate the possible role of a G-protein/cyclic AMP signaling pathway, the gene encoding GNA3, which belongs to the adenylate cyclase-activating class III of G-alpha subunits, was cloned. gna3 is clustered in tandem with the mitogen-activated protein kinase gene tmk3 and the glycogen phosphorylase gene gph1. The gna3 transcript is upregulated in the presence of light and is almost absent in the dark. A strain bearing a constitutively activated version of GNA3 (gna3QL) exhibits strongly increased cellulase transcription in the presence of the inducer cellulose and in the presence of light, whereas a gna3 antisense strain showed delayed cellulase transcription under this condition. However, the gna3QL mutant strain was unable to form cellulases in the absence of cellulose. The necessity of light for stimulation of cellulase transcription by GNA3 could not be overcome in a mutant which expressed gna3 under control of the constitutive gpd1 promoter also in darkness. We conclude that the previously reported stimulation of cellulase gene transcription by light, but not the direct transmission of the cellulose signal, involves the function and activation of GNA3. The upregulation of gna3 by light is influenced by the light modulator ENVOY, but GNA3 itself has no effect on transcription of the light regulator genes blr1, blr2, and env1. Our data for the first time imply an involvement of a G-alpha subunit in a light-dependent signaling event in fungi.
* Corresponding author. Mailing address: Research Area Gene Technology and Applied Biochemistry, Institute for Chemical Engineering, Vienna University of Technology, Getreidemarkt 9/1665, Vienna 1060, Austria. Phone: 43 1 58801 17227. Fax: 43 1 58801 17299. E-mail: mschmoll{at}mail.zserv.tuwien.ac.at
Published ahead of print on 9 January 2009.
Supplemental material for this article may be found at http://ec.asm.org/.
Present address: Laboratório de Enzimologia, Instituto de Ciências Biológicas, Departamento de Biologia Celular, Universidade de Brasilia, Asa Norte, 70910-900 Brasilia DF, Brazil.
Eukaryotic Cell, March 2009, p. 410-420, Vol. 8, No. 3
1535-9778/09/$08.00+0 doi:10.1128/EC.00256-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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