DIFFERENTIAL EXPRESSION OF THE VEGETATIVE AND SPORE-BOUND HYDROPHOBINS OF TRICHODERMA-REESEI - CLONING AND CHARACTERIZATION OF THE HFB2 GENE

The hfb2 gene encoding the hydrophobin HFBII of the filamentous fungus Trichoderma reesei was isolated by heterologous hybridization using t he vegetative hydrophobin I, hfb1, gene of T. reesei as a probe. The h fb2 gene codes for a typical fungal secreted hydrophobin of 71 amino a cids containing eight cysteine residues. The amino acid similarity tow ards HFBI is 69%. The HFBII protein was isolated from the fungal spore s by extraction with trifluoroacetic acid/acetonitrile solution, and b y bubbling from the lactose-based culture medium. Expression of the hf b1 and hfb2 genes is divergent, hfb1 expression was only observed in v egetative cultures on glucose-containing and sorbitol-containing media . It was not expressed on media containing complex plant polysaccharid es, cellulose, xylan, cellobiose or lactose, whereas hfb2 was highly e xpressed in vegetative cultures on these media. Expression of hfb2 was also strongly induced by N and C starvation, by light and in conidiat ing cultures.