Hydrophobin Genes Involved in Formation of Aerial Hyphae and Fruit Bodies in Schizophyllum

Abstract

Fungi typically grow by apical extension of hyphae that penetrate moist substrates. After establishing a branched feeding mycelium, the hyphae differentiate and grow away from the substrate into the air where they form various structures such as aerial hyphae and mushrooms. In the basidiomycete species Schizophyllum commune, we previously identified a family of homologous genes that code for small cysteine-rich hydrophobic proteins. We now report that the encoded hydrophobins are excreted in abundance into the culture medium by submerged feeding hyphae but form highly insoluble complexes in the walls of emerging hyphae. The Sc3 gene encodes a hydrophobin present in walls of aerial hyphae. The homologous Sc1 and Sc4 genes, which are regulated by the mating-type genes, encode hydrophobins present in walls of fruit body hyphae. The hydrophobins are probably instrumental in the emergence of these aerial structures.

The Role of the Extracellular Matrix (ECM) in Phytopathogenic Fungi: A Potential Target for Disease Control

“…Class I hydrophobins form highly insoluble polymers, whereas class II hydrophobins form polymers that are soluble in some organic solvents (Sunde et al, 2008). These hydrophobins are differentially expressed during the growth stage, and seem to have different functions (Nielsen et al, 2001;Segers et al, 1999;Wessels et al, 1991;Whiteford et al, 2004). In M. oryzae, two hydrophobins are well characterized: class I Mpg1 (Talbot et al, 1993) and class II Mhp1 (Kim et al, 2005).…”

Complementation of the Mpg1 mutant phenotype in Magnaporthe grisea reveals functional relationships between fungal hydrophobins

“…This 'easily wettable' phenotype is due to the absence of a hydrophobin-encoded protein layer on the surface of conidia (Templeton et al, 1995). In the mushroom Schizophyllum commune, four hydrophobin genes have been described-SC1, SC3, SC4 and SC6 (Wessels et al, 1991;Wessels, 1997)-and are differentially expressed during development of fruit bodies. SC3, a hydrophobin which is produced during hyphal growth, is required for production of upwardly projecting aerial hyphae as sc3 -gene disruption mutants are unable to form hydrophobic aerial structures (van Wetter et al, 1996).…”

Applications of hydrophobins: current state and perspectives

“…Hydrophobins self-assemble at hydrophilic-hydrophobic interfaces such as those between water and air, water and oil, and water and hydrophobic solids. Class I hydrophobins assemble into a very stable, amyloid-like membrane that can only be dissociated using trifluoroacetic acid (TFA) and formic acid (Wessels et al 1991;de Vries et al 1993). In contrast, class II hydrophobins do not assemble into amyloidlike fibrils and can be dissociated in 60 % ethanol, in 2 % SDS, or by applying pressure .…”