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Applied and Environmental Microbiology, May 2009, p. 3222-3229, Vol. 75, No. 10
0099-2240/09/$08.00+0     doi:10.1128/AEM.01764-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Differential Regulation and Posttranslational Processing of the Class II Hydrophobin Genes from the Biocontrol Fungus Hypocrea atroviridis{triangledown}

Marianna Mikus,1 Lóránt Hatvani,1,2 Torsten Neuhof,3 Monika Komon-Zelazowska,1 Ralf Dieckmann,3 Torsten Schwecke,5 Irina S. Druzhinina,1 Hans von Döhren,4 and Christian P. Kubicek1*

FB Gentechnik und Angewandte Biochemie, Institut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften, TU Wien, Getreidemarkt 9-166, 1060 Vienna, Austria,1 Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Közép fasor 52, H-6726 Szeged, Hungary,2 Anagnostec GmbH, Biotechnologiepark TGZ II, 14943 Luckenwalde, Germany,3 TU Berlin, Institut für Chemie, FG Biochemie und Molekulare Biologie, Franklinstr. 29, 10587 Berlin, Germany,4 Robert-Koch-Institut Berlin, Nordufer 20, D-13353 Berlin, Germany5

Received 31 July 2008/ Accepted 16 March 2009

Hydrophobins are small extracellular proteins, unique to and ubiquitous in filamentous fungi, which mediate interactions between the fungus and environment. The mycoparasitic fungus Hypocrea atroviridis has recently been shown to possess 10 different class II hydrophobin genes, which is a much higher number than that of any other ascomycete investigated so far. In order to learn the potential advantage of this hydrophobin multiplicity for the fungus, we have investigated their expression patterns under different physiological conditions (e.g., vegetative growth), various conditions inducing sporulation (light, carbon starvation, and mechanical injury-induced stress), and confrontation with potential hosts for mycoparasitism. The results show that the 10 hydrophobins display different patterns of response to these conditions: one hydrophobin (encoded by hfb-2b) is constitutively induced under all conditions, whereas other hydrophobins were formed only under conditions of carbon starvation (encoded by hfb-1c and hfb-6c) or light plus carbon starvation (encoded by hfb-2c, hfb-6a, and hfb-6b). The hydrophobins encoded by hfb-1b and hfb-5a were primarily formed during vegetative growth and under mechanical injury-provoked stress. hfb-22a was not expressed under any conditions and is likely a pseudogene. None of the 10 genes showed a specific expression pattern during mycoparasitic interaction. Most, but not all, of the expression patterns under the three different conditions of sporulation were dependent on one or both of the two blue-light regulator proteins BLR1 and BLR2, as shown by the use of respective loss-of-function mutants. Matrix-assisted laser desorption ionization-time of flight mass spectrometry of mycelial solvent extracts provided sets of molecular ions corresponding to HFB-1b, HFB-2a, HFB-2b, and HFB-5a in their oxidized and processed forms. These in silico-deduced sequences of the hydrophobins indicate cleavages at known signal peptide sites as well as additional N- and C-terminal processing. Mass peaks observed during confrontation with plant-pathogenic fungi indicate further proteolytic attack on the hydrophobins. Our study illustrates both divergent and redundant functions of the 10 hydrophobins of H. atroviridis.

* Corresponding author. Mailing address: Section of Microbial Biochemistry and Gene Technology, Institute of Chemical Engineering, Technische Universität Wien, Getreidemarkt 9-166, Vienna A-1060, Austria. Phone: 43 1 58801 17250. Fax: 43 1 58801 17299. E-mail: ckubicek{at}mail.zserv.tuwien.ac.at

{triangledown} Published ahead of print on 27 March 2009.

Applied and Environmental Microbiology, May 2009, p. 3222-3229, Vol. 75, No. 10
0099-2240/09/$08.00+0     doi:10.1128/AEM.01764-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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